Bio


Professor Okamura received the BS degree from the University of California at Berkeley in 1994, and the MS and PhD degrees from Stanford University in 1996 and 2000, respectively, all in mechanical engineering. She is currently Associate Professor in the mechanical engineering department at Stanford University. She was previously Professor and Vice Chair of mechanical engineering at Johns Hopkins University. She has been an associate editor of the IEEE Transactions on Haptics, an editor of the IEEE International Conference on Robotics and Automation Conference Editorial Board, and co-chair of the IEEE Haptics Symposium. Her awards include the 2009 IEEE Technical Committee on Haptics Early Career Award, the 2005 IEEE Robotics and Automation Society Early Academic Career Award, and the 2004 NSF CAREER Award. She is an IEEE Fellow. Her academic interests include haptics, teleoperation, virtual environments and simulators, medical robotics, neuromechanics and rehabilitation, prosthetics, and engineering education. Outside academia, she enjoys spending time with her husband and two children, running, and playing ice hockey.

Academic Appointments


Honors & Awards


  • Robert Bosch Faculty Scholar, Stanford University (2011-2015)
  • Fellow, IEEE (2010)
  • Early Career Award, IEEE Technical Committee on Haptics (2009)
  • CAREER Award, National Science Foundation (2004-2009)
  • Alumni Distinguished Scholar, Stanford University (2008)
  • Decker Faculty Scholar, Johns Hopkins University (2007-2010)
  • Award for Excellence, Outstanding Paper of the Year in Industrial Robot, Literati Club (2005)
  • Early Academic Career Award, IEEE Robotics and Automation Society (2005)
  • Diversity Recognition Award, Johns Hopkins University (2003)

Professional Education


  • BS, University of California, Berkeley, Mechanical Engineering (1994)
  • MS, Stanford University, Mechanical Engineering (1996)
  • PhD, Stanford University, Mechanical Engineering (2000)

2014-15 Courses


All Publications


  • Learning and generalization in an isometric visuomotor task JOURNAL OF NEUROPHYSIOLOGY Rotella, M. F., Nisky, I., Koehler, M., Rinderknecht, M. D., Bastian, A. J., Okamura, A. M. 2015; 113 (6): 1873-1884

    Abstract

    Adaptation is a prominent feature of the human motor system and has been studied extensively in reaching movements. This study characterizes adaptation and generalization during isometric reaching in which the arm remains stationary and the participant controls a virtual cursor via force applied by the hand. We measured how learning of a visual cursor rotation generalizes across workspace 1) to determine the coordinate system that predominates visual rotation learning, and 2) to ascertain whether mapping type, namely position or velocity control, influences transfer. Participants performed virtual reaches to one of two orthogonal training targets with the applied rotation. In a new workspace, participants reached to a single target, similar to the training target in either hand or joint space. Furthermore, a control experiment measured within-workspace generalization to an orthogonal target. Across position and velocity mappings, learning transferred predominantly in intrinsic (joint) space, although the transfer was incomplete. The velocity mapping resulted in significantly larger aftereffects and broader within-workspace generalization than the position mapping, potentially due to slower peak speeds, longer trial times, greater target overshoot, or other factors. Although we cannot rule out a mixed reference frame in our task, the predominance of intrinsic coding of cursor kinematics in the isometric environment opposes the extrinsic coding of arm kinematics in real reaching but matches the intrinsic coding of dynamics found in prior work. These findings have implications for the design of isometric control systems in human-machine interaction or in rehabilitation when coordinated multi-degree-of-freedom movement is difficult to achieve.

    View details for DOI 10.1152/jn.00255.2014

    View details for Web of Science ID 000350994900016

    View details for PubMedID 25520430

  • Controllable Surface Haptics via Particle Jamming and Pneumatics IEEE TRANSACTIONS ON HAPTICS Stanley, A. A., Okamura, A. M. 2015; 8 (1): 20-30

    Abstract

    The combination of particle jamming and pneumatics allows the simultaneous control of shape and mechanical properties in a tactile display. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to expand existing physical models of jamming at the inter-particle level to define the rheological characteristics of jammed systems from a macroscopic perspective, relevant to force-displacement interactions that would be experienced by human users. Force-displacement data show that a jammed cell in compression fits a Maxwell model and a cell deflected in the center while supported only at the edges fits a Zener model, each with stiffness and damping parameters that increase at higher levels of applied vacuum. This provides framework to tune and control the mechanical properties of a jamming haptic interface.

    View details for DOI 10.1109/TOH.2015.2391093

    View details for Web of Science ID 000351767000004

    View details for PubMedID 25594980

  • Uncontrolled Manifold Analysis of Arm Joint Angle Variability During Robotic Teleoperation and Freehand Movement of Surgeons and Novices IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Nisky, I., Hsieh, M. H., Okamura, A. M. 2014; 61 (12): 2869-2881
  • 3-D Ultrasound-Guided Robotic Needle Steering in Biological Tissue IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Adebar, T. K., Fletcher, A. E., Okamura, A. M. 2014; 61 (12): 2899-2910
  • Cerebellar ataxia impairs modulation of arm stiffness during postural maintenance JOURNAL OF NEUROPHYSIOLOGY Gibo, T. L., Bastian, A. J., Okamura, A. M. 2013; 110 (7): 1611-1620

    Abstract

    Impedance control enables humans to effectively interact with their environment during postural and movement tasks, adjusting the mechanical behavior of their limbs to account for instability. Previous work has shown that people are able to selectively modulate the end-point stiffness of their arms, adjusting for varying directions of environmental disturbances. Behavioral studies also suggest that separate controllers are used for impedance modulation versus joint torque coordination. Here we tested whether people with cerebellar damage have deficits in impedance control. It is known that these individuals have poor motor coordination, which has typically been attributed to deficits in joint torque control. Subjects performed a static postural maintenance task with two different types of directional force perturbations. On average, patients with cerebellar ataxia modified stiffness differentially for the two perturbation conditions, although significantly less than age-matched control subjects. Thus cerebellar damage may impair the ability to modulate arm impedance. Surprisingly, the patients' intact ability to generally alter their limb stiffness during the postural task (albeit less than age-matched control subjects) improved their movement performance in a subsequent tracing task. The transfer of stiffness control from the static to the movement task may be a strategy that can be used by patients to compensate for their motor deficits.

    View details for DOI 10.1152/jn.00294.2013

    View details for Web of Science ID 000325346300015

    View details for PubMedID 23843434

  • Predictive Modeling by the Cerebellum Improves Proprioception JOURNAL OF NEUROSCIENCE Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2013; 33 (36): 14301-14306

    Abstract

    Because sensation is delayed, real-time movement control requires not just sensing, but also predicting limb position, a function hypothesized for the cerebellum. Such cerebellar predictions could contribute to perception of limb position (i.e., proprioception), particularly when a person actively moves the limb. Here we show that human cerebellar patients have proprioceptive deficits compared with controls during active movement, but not when the arm is moved passively. Furthermore, when healthy subjects move in a force field with unpredictable dynamics, they have active proprioceptive deficits similar to cerebellar patients. Therefore, muscle activity alone is likely insufficient to enhance proprioception and predictability (i.e., an internal model of the body and environment) is important for active movement to benefit proprioception. We conclude that cerebellar patients have an active proprioceptive deficit consistent with disrupted movement prediction rather than an inability to generally enhance peripheral proprioceptive signals during action and suggest that active proprioceptive deficits should be considered a fundamental cerebellar impairment of clinical importance.

    View details for DOI 10.1523/JNEUROSCI.0784-13.2013

    View details for Web of Science ID 000324165500004

    View details for PubMedID 24005283

  • Characterization and Psychophysical Studies of an Air-Jet Lump Display IEEE TRANSACTIONS ON HAPTICS Gwilliam, J. C., Bianchi, M., Su, L. K., Okamura, A. M. 2013; 6 (2): 156-166
  • Coaxial Needle Insertion Assistant With Enhanced Force Feedback IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING De Lorenzo, D., Koseki, Y., De Momi, E., Chinzei, K., Okamura, A. M. 2013; 60 (2): 379-389

    Abstract

    Many medical procedures involving needle insertion into soft tissues, such as anesthesia, biopsy, brachytherapy, and placement of electrodes, are performed without image guidance. In such procedures, haptic detection of changing tissue properties at different depths during needle insertion is important for needle localization and detection of subsurface structures. However, changes in tissue mechanical properties deep inside the tissue are difficult for human operators to sense, because the relatively large friction force between the needle shaft and the surrounding tissue masks the smaller tip forces. A novel robotic coaxial needle insertion assistant, which enhances operator force perception, is presented. This one-degree-of-freedom cable-driven robot provides to the operator a scaled version of the force applied by the needle tip to the tissue, using a novel design and sensors that separate the needle tip force from the shaft friction force. The ability of human operators to use the robot to detect membranes embedded in artificial soft tissue was tested under the conditions of 1) tip force and shaft force feedback, and 2) tip force only feedback. The ratio of successful to unsuccessful membrane detections was significantly higher (up to 50%) when only the needle tip force was provided to the user.

    View details for DOI 10.1109/TBME.2012.2227316

    View details for Web of Science ID 000316809800013

    View details for PubMedID 23193302

  • Perception of Springs With Visual and Proprioceptive Motion Cues: Implications for Prosthetics IEEE TRANSACTIONS ON HUMAN-MACHINE SYSTEMS Gurari, N., Kuchenbecker, K. J., Okamura, A. M. 2013; 43 (1): 102-114
  • Behavior of Tip-Steerable Needles in Ex Vivo and In Vivo Tissue IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Majewicz, A., Marra, S. P., van Vledder, M. G., Lin, M., Choti, M. A., Song, D. Y., Okamura, A. M. 2012; 59 (10): 2705-2715

    Abstract

    Robotic needle steering is a promising technique to improve the effectiveness of needle-based clinical procedures, such as biopsies and ablation, by computer-controlled, curved insertions of needles within solid organs. In this paper, we explore the capabilities, challenges, and clinical relevance of asymmetric-tip needle steering through experiments in ex vivo and in vivo tissue. We evaluate the repeatability of needle insertion in inhomogeneous biological tissue and compare ex vivo and in vivo needle curvature and insertion forces. Steerable needles curved more in kidney than in liver and prostate, likely due to differences in tissue properties. Pre-bent needles produced higher insertion forces in liver and more curvature in vivo than ex vivo. When compared to straight stainless steel needles, steerable needles did not cause a measurable increase in tissue damage and did not exert more force during insertion. The minimum radius of curvature achieved by prebent needles was 5.23 cm in ex vivo tissue, and 10.4 cm in in vivo tissue. The curvatures achieved by bevel tip needles were negligible for in vivo tissue. The minimum radius of curvature for bevel tip needles in ex vivo tissue was 16.4 cm; however, about half of the bevel tip needles had negligible curvatures. We also demonstrate a potential clinical application of needle steering by targeting and ablating overlapping regions of cadaveric canine liver.

    View details for DOI 10.1109/TBME.2012.2204749

    View details for Web of Science ID 000308989000003

    View details for PubMedID 22711767

  • Feature detection for haptic exploration with robotic fingers INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Okamura, A. M., Cutkosky, M. R. 2001; 20 (12): 925-938
  • Reality-based models for vibration feedback in virtual environments IEEE-ASME TRANSACTIONS ON MECHATRONICS Okamura, A. M., Cutkosky, M. R., Dennerlein, J. T. 2001; 6 (3): 245-252
  • Artificial Tactile Sensing of Position and Slip Speed by Exploiting Geometrical Features IEEE-ASME TRANSACTIONS ON MECHATRONICS Damian, D. D., Newton, T. H., Pfeifer, R., Okamura, A. M. 2015; 20 (1): 263-274
  • Augmentation Of Stiffness Perception With a 1-Degree-of-Freedom Skin Stretch Device IEEE TRANSACTIONS ON HUMAN-MACHINE SYSTEMS Quek, Z. F., Schorr, S. B., Nisky, I., Okamura, A. M., Provancher, W. R. 2014; 44 (6): 731-742
  • Testing models of cerebellar ataxia via dynamic simulation ROBOTICA Grow, D., Bastian, A. J., Okamura, A. M. 2014; 32 (8): 1383-1397
  • Torsional Dynamics of Steerable Needles: Modeling and Fluoroscopic Guidance IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Swensen, J. P., Lin, M., Okamura, A. M., Cowan, N. J. 2014; 61 (11): 2707-2717
  • Neural coding of passive lump detection in compliant artificial tissue. Journal of neurophysiology Gwilliam, J. C., Yoshioka, T., Okamura, A. M., Hsiao, S. S. 2014; 112 (5): 1131-1141

    Abstract

    Here, we investigate the neural mechanisms of detecting lumps embedded in artificial compliant tissues. We performed a combined psychophysical study of humans performing a passive lump detection task with a neurophysiological study in nonhuman primates (Macaca mulatta) where we recorded the responses of peripheral mechanoreceptive afferents to lumps embedded at various depths in intermediates (rubbers) of varying compliance. The psychophysical results reveal that human lump detection is greatly degraded by both lump depth and decreased compliance of the intermediate. The neurophysiology results reveal that only the slowly adapting type 1 (SA1) afferents provide a clear spatial representation of lumps at all depths and that the representation is affected by lump size, depth, and compliance of the intermediate. The rapidly adapting afferents are considerably less sensitive to the lump. We defined eight neural response measures that we hypothesized could explain the psychophysical behavior, including peak firing rate, spatial spread of neural activity, and additional parameters derived from these measures. We find that peak firing rate encodes the depth of the lump, and the neural spatial spread of the SA1 response encodes for lump size but not lump shape. We also find that the perception of lump size may be affected by the compliance of the intermediate. The results show that lump detection is based on a spatial population code of the SA1 afferents, which is distorted by the depth of the lump and compliance of the tissue.

    View details for DOI 10.1152/jn.00032.2013

    View details for PubMedID 24805077

  • Effects of robotic manipulators on movements of novices and surgeons SURGICAL ENDOSCOPY AND OTHER INTERVENTIONAL TECHNIQUES Nisky, I., Okamura, A. M., Hsieh, M. H. 2014; 28 (7): 2145-2158

    Abstract

    Robot-assisted surgery is widely adopted for many procedures but has not realized its full potential to date. Based on human motor control theories, the authors hypothesized that the dynamics of the master manipulators impose challenges on the motor system of the user and may impair performance and slow down learning. Although studies have shown that robotic outcomes are correlated with the case experience of the surgeon, the relative contribution of cognitive versus motor skill is unknown. This study quantified the effects of da Vinci Si master manipulator dynamics on movements of novice users and experienced surgeons and suggests possible implications for training and robot design.In the reported study, six experienced robotic surgeons and ten novice nonmedical users performed movements under two conditions: teleoperation of a da Vinci Si Surgical system and freehand. A linear mixed model was applied to nine kinematic metrics (including endpoint error, movement time, peak speed, initial jerk, and deviation from a straight line) to assess the effects of teleoperation and expertise. To assess learning effects, t tests between the first and last movements of each type were used.All the users moved slower during teleoperation than during freehand movements (F 1,9343 = 345; p < 0.001). The experienced surgeons had smaller errors than the novices (F 1,14 = 36.8; p < 0.001). The straightness of movements depended on their direction (F 7,9343 = 117; p < 0.001). Learning effects were observed in all conditions. Novice users first learned the task and then the dynamics of the manipulator.The findings showed differences between the novices and the experienced surgeons for extremely simple point-to-point movements. The study demonstrated that manipulator dynamics affect user movements, suggesting that these dynamics could be improved in future robot designs. The authors showed the partial adaptation of novice users to the dynamics. Future studies are needed to evaluate whether it will be beneficial to include early training sessions dedicated to learning the dynamics of the manipulator.

    View details for DOI 10.1007/s00464-014-3446-5

    View details for Web of Science ID 000338278800017

  • Predicting and correcting ataxia using a model of cerebellar function BRAIN Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2014; 137: 1931-1944
  • Predicting and correcting ataxia using a model of cerebellar function. Brain Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2014; 137: 1931-1944

    Abstract

    Cerebellar damage results in uncoordinated, variable and dysmetric movements known as ataxia. Here we show that we can reliably model single-joint reaching trajectories of patients (n = 10), reproduce patient-like deficits in the behaviour of controls (n = 11), and apply patient-specific compensations that improve reaching accuracy (P < 0.02). Our approach was motivated by the theory that the cerebellum is essential for updating and/or storing an internal dynamic model that relates motor commands to changes in body state (e.g. arm position and velocity). We hypothesized that cerebellar damage causes a mismatch between the brain's modelled dynamics and the actual body dynamics, resulting in ataxia. We used both behavioural and computational approaches to demonstrate that specific cerebellar patient deficits result from biased internal models. Our results strongly support the idea that an intact cerebellum is critical for maintaining accurate internal models of dynamics. Importantly, we demonstrate how subject-specific compensation can improve movement in cerebellar patients, who are notoriously unresponsive to treatment.

    View details for DOI 10.1093/brain/awu115

    View details for PubMedID 24812203

  • Task-dependent impedance and implications for upper-limb prosthesis control INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Blank, A. A., Okamura, A. M., Whitcomb, L. L. 2014; 33 (6): 827-846
  • Haptic feedback enhances rhythmic motor control by reducing variability, not improving convergence rate JOURNAL OF NEUROPHYSIOLOGY Ankarali, M. M., Sen, H. T., De, A., Okamura, A. M., Cowan, N. J. 2014; 111 (6): 1286-1299

    Abstract

    Stability and performance during rhythmic motor behaviors such as locomotion are critical for survival across taxa: falling down would bode well for neither cheetah nor gazelle. Little is known about how haptic feedback, particularly during discrete events such as the heel-strike event during walking, enhances rhythmic behavior. To determine the effect of haptic cues on rhythmic motor performance, we investigated a virtual paddle juggling behavior, analogous to bouncing a table tennis ball on a paddle. Here, we show that a force impulse to the hand at the moment of ball-paddle collision categorically improves performance over visual feedback alone, not by regulating the rate of convergence to steady state (e.g., via higher gain feedback or modifying the steady-state hand motion), but rather by reducing cycle-to-cycle variability. This suggests that the timing and state cues afforded by haptic feedback decrease the nervous system's uncertainty of the state of the ball to enable more accurate control but that the feedback gain itself is unaltered. This decrease in variability leads to a substantial increase in the mean first passage time, a measure of the long-term metastability of a stochastic dynamical system. Rhythmic tasks such as locomotion and juggling involve intermittent contact with the environment (i.e., hybrid transitions), and the timing of such transitions is generally easy to sense via haptic feedback. This timing information may improve metastability, equating to less frequent falls or other failures depending on the task.

    View details for DOI 10.1152/jn.00140.2013

    View details for Web of Science ID 000335775500012

    View details for PubMedID 24371296

  • Mapping Stiffness Perception in the Brain with an fMRI-Compatible Particle-Jamming Haptic Interface 2014 36TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Menon, S., Stanley, A. A., Zhu, J., Okamura, A. M., Khatib, O. 2014: 2051-2056

    Abstract

    We demonstrate reliable neural responses to changes in haptic stiffness perception using a functional magnetic resonance imaging (fMRI) compatible particle-jamming haptic interface. Our haptic interface consists of a silicone tactile surface whose stiffness we can control by modulating air-pressure in a sub-surface pouch of coarsely ground particles. The particles jam together as the pressure decreases, which stiffens the surface. During fMRI acquisition, subjects performed a constant probing task, which involved continuous contact between the index fingertip and the interface and rhythmic increases and decreases in fingertip force (1.6 Hz) to probe stiffness. Without notifying subjects, we randomly switched the interface's stiffness (switch time, 300-500 ms) from soft (200 N/m) to hard (1400 N/m). Our experiment design's constant motor activity and cutaneous tactile sensation helped disassociate neural activation for both from stiffness perception, which helped localized it to a narrow region in somatosensory cortex near the supra-marginal gyrus. Testing different models of neural activation, we found that assuming indepedent stiffness-change responses at both soft-hard and hard-soft transitions provides the best explanation for observed fMRI measurements (three subjects; nine four-minute scan runs each). Furthermore, we found that neural activation related to stiffness-change and absolute stiffness can be localized to adjacent but disparate anatomical locations. We also show that classical finger-tapping experiments activate a swath of cortex and are not suitable for localizing stiffness perception. Our results demonstrate that decorrelating motor and sensory neural activation is essential for characterizing somatosensory cortex, and establish particle-jamming haptics as an attractive low-cost method for fMRI experiments.

    View details for Web of Science ID 000350044702010

    View details for PubMedID 25570387

  • Integration of a Particle Jamming Tactile Display with a Cable-Driven Parallel Robot HAPTICS: NEUROSCIENCE, DEVICES, MODELING, AND APPLICATIONS, PT II Stanley, A. A., Mayhew, D., Irwin, R., Okamura, A. M. 2014; 8619: 258-265
  • Recursive Estimation of Needle Pose for Control of 3D-Ultrasound-Guided Robotic Needle Steering 2014 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS (IROS 2014) Adebar, T. K., Okamura, A. M. 2014: 4303-4308
  • Grip Force Control during Virtual Object Interaction: Effect of Force Feedback, Accuracy Demands, and Training IEEE TRANSACTIONS ON HAPTICS Gibo, T. L., Bastian, A. J., Okamura, A. M. 2014; 7 (1): 37-47

    Abstract

    When grasping and manipulating objects, people are able to efficiently modulate their grip force according to the experienced load force. Effective grip force control involves providing enough grip force to prevent the object from slipping, while avoiding excessive force to avoid damage and fatigue. During indirect object manipulation via teleoperation systems or in virtual environments, users often receive limited somatosensory feedback about objects with which they interact. This study examines the effects of force feedback, accuracy demands, and training on grip force control during object interaction in a virtual environment. The task required subjects to grasp and move a virtual object while tracking a target. When force feedback was not provided, subjects failed to couple grip and load force, a capability fundamental to direct object interaction. Subjects also exerted larger grip force without force feedback and when accuracy demands of the tracking task were high. In addition, the presence or absence of force feedback during training affected subsequent performance, even when the feedback condition was switched. Subjects' grip force control remained reminiscent of their employed grip during the initial training. These results motivate the use of force feedback during telemanipulation and highlight the effect of force feedback during training.

    View details for DOI 10.1109/TOH.2013.60

    View details for Web of Science ID 000336913100005

    View details for PubMedID 24845744

  • Cerebellar motor learning: are environment dynamics more important than error size? JOURNAL OF NEUROPHYSIOLOGY Gibo, T. L., Criscimagna-Hemminger, S. E., Okamura, A. M., Bastian, A. J. 2013; 110 (2): 322-333

    Abstract

    Cerebellar damage impairs the control of complex dynamics during reaching movements. It also impairs learning of predictable dynamic perturbations through an error-based process. Prior work suggests that there are distinct neural mechanisms involved in error-based learning that depend on the size of error experienced. This is based, in part, on the observation that people with cerebellar degeneration may have an intact ability to learn from small errors. Here we studied the relative effect of specific dynamic perturbations and error size on motor learning of a reaching movement in patients with cerebellar damage. We also studied generalization of learning within different coordinate systems (hand vs. joint space). Contrary to our expectation, we found that error size did not alter cerebellar patients' ability to learn the force field. Instead, the direction of the force field affected patients' ability to learn, regardless of whether the force perturbations were introduced gradually (small error) or abruptly (large error). Patients performed best in fields that helped them compensate for movement dynamics associated with reaching. However, they showed much more limited generalization patterns than control subjects, indicating that patients rely on a different learning mechanism. We suggest that patients typically use a compensatory strategy to counteract movement dynamics. They may learn to relax this compensatory strategy when the external perturbation is favorable to counteracting their movement dynamics, and improve reaching performance. Altogether, these findings show that dynamics affect learning in cerebellar patients more than error size.

    View details for DOI 10.1152/jn.00745.2012

    View details for Web of Science ID 000321843800005

    View details for PubMedID 23596337

  • Novel algorithm for real-time onset detection of surface electromyography in step-tracking wrist movements. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Kuroda, Y., Nisky, I., Uranishi, Y., Imura, M., Okamura, A. M., Oshiro, O. 2013; 2013: 2056-2059

    Abstract

    We present a novel algorithm for real-time detection of the onset of surface electromyography signal in step-tracking wrist movements. The method identifies abrupt increase of the quasi-tension signal calculated from sEMG resulting from the step-by-step recruitment of activated motor units. We assessed the performance of our proposed algorithm using both simulated and real sEMG signals, and compared with two existing detection methods. Evaluation with simulated sEMG showed that the detection accuracy of our method is robust to different signal-to-noise ratios, and that it outperforms the existing methods in terms of bias when the noise is large (low SNR). Evaluation with real sEMG analysis also indicated better detection performance compared to existing methods.

    View details for DOI 10.1109/EMBC.2013.6609936

    View details for PubMedID 24110123

  • The effect of a robot-assisted surgical system on the kinematics of user movements. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Nisky, I., Hsieh, M. H., Okamura, A. M. 2013; 2013: 6257-6260

    Abstract

    Teleoperated robot-assisted surgery (RAS) offers many advantages over traditional minimally invasive surgery. However, RAS has not yet realized its full potential, and it is not clear how to optimally train surgeons to use these systems. We hypothesize that the dynamics of the master manipulator impact the ability of users to make desired movements with the robot. We compared freehand and teleoperated movements of novices and experienced surgeons. To isolate the effects of dynamics from procedural knowledge, we chose simple movements rather than surgical tasks. We found statistically significant effects of teleoperation and user expertise in several aspects of motion, including target acquisition error, movement speed, and movement smoothness. Such quantitative assessment of human motor performance in RAS can impact the design of surgical robots, their control, and surgeon training methods, and eventually, improve patient outcomes.

    View details for DOI 10.1109/EMBC.2013.6610983

    View details for PubMedID 24111170

  • Adaptation to visuomotor rotation in isometric reaching is similar to movement adaptation. IEEE ... International Conference on Rehabilitation Robotics : [proceedings] Rotella, M. F., Koehler, M., Nisky, I., Bastian, A. J., Okamura, A. M. 2013; 2013: 1-6

    Abstract

    Isometric reaching, in which the arm remains stationary and the user controls a virtual cursor via force input, is a motor task that has not been thoroughly compared to real reaching. In this study, we ask if isometric adaptation to a kinematic perturbation is similar to adaptation in movement, and if the type of isometric mapping (position or velocity control) influences learning. Healthy subjects made real and virtual reaches with the arm in plane. In some trials, the cursor was rotated counter clockwise by 45° to perturb the kinematic mapping. To assess adaptation, the angular error of cursor movement at 150 ms from movement onset was measured for each reach; error was averaged across subjects and a two-state learning mode was fit to error data. For movement and isometric groups, average angular error peaked at perturbation onset, reduced over 200 reaches, and reversed direction when the perturbation was removed. We show that subjects are able to adapt to a visuomotor rotation in both position- and velocity-based cursor control, and that the time course of adaptation resembles that of movement adaptation. Training of virtual reaching using force/torque input could be particularly applicable for stroke patients with significant movement deficits, who could benefit from intensive treatments using simple, cost-effective devices.

    View details for DOI 10.1109/ICORR.2013.6650431

    View details for PubMedID 24187249

  • Effect of age on stiffness modulation during postural maintenance of the arm. IEEE ... International Conference on Rehabilitation Robotics : [proceedings] Gibo, T. L., Bastian, A. J., Okamura, A. M. 2013; 2013: 1-6

    Abstract

    The ability to modify the mechanical impedance of our limbs allows us to perform a variety of motor control tasks while interacting with the environment in a stable manner. Prior work has shown that young, healthy people are capable of modulating arm stiffness via selective muscle co-contraction to account for external disturbances in various directions. Increased age detrimentally affects control of movement and stability, although the neural mechanisms underlying these deficits are not entirely understood. In this study, younger and older subjects performed a static postural maintenance task with two types of directional force perturbations. Older individuals showed significantly less stiffness modification between the two perturbation conditions compared to the younger individuals, indicating less optimal modulation of arm impedance. This impairment should be considered during motor control evaluation in older populations, whether it be activities of daily living or skill assessment.

    View details for DOI 10.1109/ICORR.2013.6650395

    View details for PubMedID 24187214

  • Characterization and psychophysical studies of an air-jet lump display. IEEE transactions on haptics Gwilliam, J. C., Bianchi, M., Su, L. K., Okamura, A. M. 2013; 6 (2): 156-166

    Abstract

    Development of tactile displays to enhance palpation of lumps during robot-assisted minimally invasive surgery is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. This work describes the quantitative and psychophysical assessment of an air-jet tactile display that creates a lump percept by directing pressurized air through an aperture onto the finger. The air pressure and aperture size are meant to control the hardness and size, respectively, of the perceived lump. Jet impingement pressure and flow rate were measured by capacitive tactile sensors and mass flow meters at varying aperture sizes and pressures. The air-jet pressure profile width evolves as jet theory predicts and is largely independent of supply pressure (and therefore jet exit velocity). The method of constant stimuli was used to determine the just noticeable differences (JNDs) for the air pressure and aperture size. Qualitative results indicate that subjects perceive the stimulus as a "lump-like" shape. Pressure JNDs ranged from 19.6-24.4 kPag and aperture size JNDs ranged from 0.50-0.66 mm. No significant correlation exists between the supply pressure and changes in perceived lump size. However, pressure JNDs show significant (p < 0.001) inverse correlation with aperture size, with improved discrimination at larger apertures, where a greater finger pad area is stimulated.

    View details for DOI 10.1109/TOH.2012.71

    View details for PubMedID 24808300

  • Does a basic deficit in force control underlie cerebellar ataxia? JOURNAL OF NEUROPHYSIOLOGY Charles, S. K., Okamura, A. M., Bastian, A. J. 2013; 109 (4): 1107-1116

    Abstract

    Because damage to the cerebellum results in characteristic movement incoordination known as "ataxia," it has been hypothesized that it is involved in estimation of limb dynamics that occur during movement. However, cerebellar function may extend beyond movement to force control in general, with or without movement. Here we tested whether the cerebellum is involved in controlling force separate from estimating limb dynamics and whether ataxia could result from a deficit in force control. We studied patients with cerebellar ataxia controlling their arm force isometrically; in this condition arm dynamics are absent and there is no need for (or effect from an impairment in) estimations of limb dynamics. Subjects were required to control their force magnitude, direction, or both. Cerebellar patients were able to match force magnitude or direction similarly to control subjects. Furthermore, when controlling force magnitude, they intuitively chose directions (not specified) that required minimal effort at the joint level--this ability was also similar to control subjects. In contrast, cerebellar patients performed significantly worse than control subjects when asked to match both force magnitude and direction. This was surprising, since they did not exhibit significant impairment in doing either in isolation. These results show that cerebellum-dependent computations are not limited to estimations of body dynamics needed for active movement. Deficits occur even in isometric conditions, but apparently only when multiple degrees of freedom must be controlled simultaneously. Thus a fundamental cerebellar operation may be combining/coordinating degrees of freedom across many kinds of movements and behaviors.

    View details for DOI 10.1152/jn.00152.2012

    View details for Web of Science ID 000315141100021

    View details for PubMedID 23175807

  • Kinematic analysis of motor performance in robot-assisted surgery: a preliminary study. Studies in health technology and informatics Nisky, I., Patil, S., Hsieh, M. H., Okamura, A. M. 2013; 184: 302-308

    Abstract

    The inherent dynamics of the master manipulator of a teleoperated robot-assisted surgery (RAS) system can affect the movements of a human operator, in comparison with free-space movements. To measure the effects of these dynamics on operators with differing levels of surgical expertise, a da Vinci Si system was instrumented with a custom surgeon grip fixture and magnetic pose trackers. We compared users' performance of canonical motor control movements during teleoperation with the manipulator and freehand cursor control, and found significant differences in several aspects of motion, including target acquisition error, movement speed, and acceleration. In addition, there was preliminary evidence for differences between experts and novices. These findings could impact robot design, control, and training methods for RAS.

    View details for PubMedID 23400175

  • Autonomous Robotic Palpation: Machine Learning Techniques to Identify Hard Inclusions in Soft Tissues 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Nichols, K. A., Okamura, A. M. 2013: 4384-4389
  • A HAPTIC SYSTEM FOR EDUCATIONAL GAMES: DESIGN AND APPLICATION-SPECIFIC KINEMATIC OPTIMIZATION ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE, VOL 2 Kessler, J. A., Lovelace, R. C., Okamura, A. M. 2013
  • MODEL-MEDIATED TELEOPERATION WITH PREDICTIVE MODELS AND RELATIVE TRACKING ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE, VOL 2 Winck, R. C., Okamura, A. M. 2013
  • ROBOT-GUIDED SHEATHS (RoGS) FOR PERCUTANEOUS ACCESS TO THE PEDIATRIC KIDNEY: PATIENT-SPECIFIC DESIGN AND PRELIMINARY RESULTS PROCEEDINGS OF THE ASME 2013 DYNAMIC SYSTEMS AND CONTROL CONFERENCE (DSCC2013), VOL. 1 Morimoto, T. K., Hsieh, M. H., Okamura, A. M. 2013
  • A Framework for Analysis of Surgeon Arm Posture Variability in Robot-Assisted Surgery 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Nisky, I., Hsieh, M. H., Okamura, A. M. 2013: 245-251
  • Tissue Fixation by Suction Increases the Accuracy of Robotic Needle Insertion 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Wedlick, T. R., Lin, D. J., Okamura, A. M. 2013: 1694-1699
  • Sensory Substitution via Cutaneous Skin Stretch Feedback 2013 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Schorr, S. B., Quek, Z. F., Romano, R. Y., Nisky, I., Provancher, W. R., Okamura, A. M. 2013: 2341-2346
  • Sensorimotor Performance in Robot Assisted Surgery. Nisky, I., Hsieh, M., H., Okamura, A., M. 2013
  • Arm Stiffness in Patients with Cerebellar Ataxia: Modulation during Postural Maintenance and its Subsequent Effects on Movement. Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013
  • Sensory Substitution via Cutaneous Skin Stretch Feedback. Schorr, S., B., Quek, Z., F., Romano, R., Y., Nisky, I., Provancher, W., R., Okamura, A., M. 2013
  • A Haptic System for Educational Games: Design and Application-Specific Kinematic Optimization. Kessler, J., A., Lovelace, R., C., Okamura, A., M. 2013
  • A Framework for Analysis of Surgeon Arm Posture Variability in Robot-Assisted Surgery. Nisky, I., Hsieh, M., H., Okamura, A., M. 2013
  • Haptic Jamming: A Deformable Geometry, Variable Stiffness Tactile Display using Pneumatics and Particle Jamming 2013 WORLD HAPTICS CONFERENCE (WHC) Stanley, A. A., Gwilliam, J. C., Okamura, A. M. 2013: 25-30
  • Sensory Augmentation of Stiffness using Fingerpad Skin Stretch 2013 WORLD HAPTICS CONFERENCE (WHC) Quek, Z. F., Schorr, S. B., Nisky, I., Okamura, A. M., Provancher, W. R. 2013: 467-472
  • Cartesian and Joint Space Teleoperation for Nonholonomic Steerable Needles 2013 WORLD HAPTICS CONFERENCE (WHC) Majewicz, A., Okamura, A. M. 2013: 395-400
  • Novel Algorithm for Real-Time Onset Detection of Surface Electromyography in Step-Tracking Wrist Movements. Kuroda, Y., Nisky, I., Uranishi, Y., Imura, M., Okamura, A., M., Oshiro, O. 2013
  • Cerebellar Ataxia Impairs Modulation of Arm Stiffness during Postural Maintenance. Journal of Neurophysiology Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013; 7 (110): 1611-1620
  • A Haptic Display for Medical Simulation Using Particle Jamming. Medicine Meets Virtual Reality (Studies in Health Technology and Information). Stanley, A., Gwilliam, J., C., Okamura, A., M. 2013
  • 3D Segmentation of Curved Needles using Doppler Ultrasound and Vibration. Information Processing in Computer-Assisted Interventions Adebar, T., K., Okamura, A., M. 2013: 61-70
  • Kinematic Analysis of Motor Performance in Robot-Assisted Surgery: Implications for Robot Design and Surgical Training. Nisky, I., Patil, S., Hsieh, M., H., Okamura, A., M. 2013
  • Robot-Guided Sheaths (RoGS) for Percutaneous Access to the Pedatric Kidney: Patient-Specific Design and Preliminary Results. Morimoto, T., K., Hsieh, M., H., Okamura, A., M. 2013
  • Effect of Age on Stiffness Modulation during Postural Maintenance of the Arm. Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013
  • Autonomous Robotic Palpation: Machine Learning Techniques to Identify Hard Inclusions in Soft Tissues. Nichols, K., A., Okamura, A., M. 2013
  • Adaptation to Visuomotor Rotation in Isometric Virtual Reaching Parallels Learning in Movement. Rotella, M., F., Koehler, M., Nisky, I., Bastian, A., J., Okamura, A., M. 2013
  • 3D Segmentation of Curved Needles using Doppler Ultrasound and Vibration. Information Processing in Computer-Assisted Interventions Adebar, T., K., Okamura, A., M. 2013: 61-70
  • Transfer of isometric motor learning depends on the mapping of force input to cursor movement. Rotella, M., F., Koehler, M., Nisky, I., Bastian, A., J., Okamura, A., M. 2013
  • Tissue Fixation by Suction Increases the Accuracy of Robotic Needle Insertion. Wedlick, T., R., Lin, D., J., Okamura, A., M. 2013
  • Model-Mediated Teleoperation with Predictive Models and Relative Tracking. Wedlick, R., C., Okamura, A., M. 2013
  • Grip Force Control During Virtual Object Interaction: Effect of Force Feedback, Accuracy Demands, and Training. IEEE Transactions on Haptics Gibo, T., L., Bastian, A., J., Okamura, A., M. 2013

    View details for DOI 10.1109/TOH.2014.60

  • Active force perception depends on cerebellar function JOURNAL OF NEUROPHYSIOLOGY Bhanpuri, N. H., Okamura, A. M., Bastian, A. J. 2012; 107 (6): 1612-1620

    Abstract

    Damage to the cerebellum causes characteristic movement abnormalities but is thought to have minimal impact on somatosensory perception. Traditional clinical assessments of patients with cerebellar lesions reveal no perceptual deficits despite the fact that the cerebellum receives substantial somatosensory information. Given that abnormalities have been reported in predicting the visual consequences of movement, we suspect that the cerebellum broadly participates in perception when motor output is required (i.e., active perception). Thus we hypothesize that cerebellar integrity is essential for somatosensory perception that requires motor activity, but not passive somatosensory perception. We compared the perceptual acuity of human cerebellar patients to that of healthy control subjects in several different somatosensory perception tasks with minimal visual information. We found that patients were worse at active force and stiffness discrimination but similar to control subjects with regard to passive cutaneous force detection, passive proprioceptive detection, and passive proprioceptive discrimination. Furthermore, the severity of movement symptoms as assessed by a clinical exam was positively correlated with impairment of active force perception. Notably, within the context of these perceptual tasks, control subjects and cerebellar patients displayed similar movement characteristics, and hence differing movement strategies are unlikely to underlie the differences in perception. Our results are consistent with the hypothesis that the cerebellum is vital to sensory prediction of self-generated movement and suggest a general role for the cerebellum in multiple forms of active perception.

    View details for DOI 10.1152/jn.00983.2011

    View details for Web of Science ID 000302140300008

    View details for PubMedID 22190620

  • Augmented reality and haptic interfaces for robot-assisted surgery INTERNATIONAL JOURNAL OF MEDICAL ROBOTICS AND COMPUTER ASSISTED SURGERY Yamamoto, T., Abolhassani, N., Jung, S., Okamura, A. M., Judkins, T. N. 2012; 8 (1): 45-56

    Abstract

    Current teleoperated robot-assisted minimally invasive surgical systems do not take full advantage of the potential performance enhancements offered by various forms of haptic feedback to the surgeon. Direct and graphical haptic feedback systems can be integrated with vision and robot control systems in order to provide haptic feedback to improve safety and tissue mechanical property identification.An interoperable interface for teleoperated robot-assisted minimally invasive surgery was developed to provide haptic feedback and augmented visual feedback using three-dimensional (3D) graphical overlays. The software framework consists of control and command software, robot plug-ins, image processing plug-ins and 3D surface reconstructions.The feasibility of the interface was demonstrated in two tasks performed with artificial tissue: palpation to detect hard lumps and surface tracing, using vision-based forbidden-region virtual fixtures to prevent the patient-side manipulator from entering unwanted regions of the workspace.The interoperable interface enables fast development and successful implementation of effective haptic feedback methods in teleoperation.

    View details for DOI 10.1002/rcs.421

    View details for Web of Science ID 000301120100005

    View details for PubMedID 22069247

  • User comprehension of task performance with varying impedance in a virtual prosthetic arm: A pilot study 2012 4TH IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB) Blank, A., Okamura, A. M., Whitcomb, L. L. 2012: 500-507
  • Haptic Footstep Display. Jayakumar, R., P., Mishra, S., K., Dannenhoffer, J., F., Okamura, A., M. 2012
  • Development of the KineSys MedSim: A Novel Hands-Free Haptic Robot for Medical Simulation. Medicine Meets Virtual Reality (Studies in Health Technology and Information). Judkins, T., N., Stevenson, M., Mayhew, D., Okamura, A., M. 2012
  • Haptic feedback enhances rhythmic motor control performance. Ankarali, M., Mert, Sen, H., Tutkun, Okamura, Allison, M., Cowan, Noah, J. 2012
  • Predicting and correcting human ataxia using a model of cerebellar function. Bhanpuri, N., Okamura, A., M., Bastian, A., J. 2012
  • HAPI Bands: A Haptic Augmented Posture Interface. Rotella, M., F., Guerin, K., He, X., Okamura, A., M. 2012
  • Design and Control of an Air-Jet Lump Display. Gwilliam, J., C., Degirmenci, A., Bianchi, M., Okamura, A., M. 2012
  • Conveying the Configuration of a Virtual Human Hand Using Vibrotactile Feedback. Cheng, A., Nichols, K., A., Weeks, H., M., Gurari, N., Okamura, A., M. 2012
  • M-Width: Stability and Accuracy of Haptic Rendering of Virtual Mass. In Robotics: Science and Systems. Colonnese, N., Okamura, A., M. 2012
  • Discrimination of Springs with Vision, Proprioception, and Artificial Skin Stretch Cues. Gurari, N., Wheeler, J., Shelton, A., Okamura, A., M. 2012
  • Augmented Reality and Haptic Interfaces for Robot-Assisted Surgery. International Journal of Medical Robotics and Computer Assisted Surgery Yamamoto, T., Abolhassani, N., Jung, S., Okamura, A., M., Judkins, T., N. 2012; 1 (8): 45-46
  • Characterization of Robotic Needle Insertion and Rotation in Artificial and Ex Vivo Tissues 2012 4TH IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB) Wedlick, T. R., Okamura, A. M. 2012: 62-68
  • Wearable Haptic Device for Cutaneous Force and Slip Speed Display 2012 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Damian, D. D., Ludersdorfer, M., Kim, Y., Arieta, A. H., Pfeifer, R., Okamura, A. M. 2012: 1038-1043
  • Robot-Assisted Needle Steering IEEE ROBOTICS & AUTOMATION MAGAZINE Reed, K. B., Majewicz, A., Kallem, V., Alterovitz, R., Goldberg, K., Cowan, N. J., Okamura, A. M. 2011; 18 (4): 35-46
  • Haptics in Medicine and Clinical Skill Acquisition IEEE TRANSACTIONS ON HAPTICS Okamura, A. M., Basdogan, C., Baillie, S., Harwin, W. S. 2011; 4 (3): 153-154
  • Experimental evaluation of a coaxial needle insertion assistant with enhanced force feedback 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) De Lorenzo, D., Koseki, Y., De Momi, E., Chinzei, K., Okamura, A. M. 2011: 3447-3450

    Abstract

    During needle insertion in soft tissue, detection of change in tissue properties is important both for diagnosis to detect pathological tissue and for prevention to avoid puncture of important structures. The presence of a membrane located deep inside the tissue results in a relatively small force variation at the needle tip that can be masked by relatively large friction force between the needle shaft and the surrounding tissue. Also, user perception of force can be limited due to the overall small force amplitude in some applications (e.g. brain surgery). A novel robotic coaxial needle insertion assistant was developed to enhance operator force perception. The coaxial needle separates the cutting force at the needle tip from shear friction on the needle shaft. The assistant is force controlled (admittance control), providing the operator with force feedback that is a scaled version of the force applied by the needle tip to the tissue. The effectiveness of the assistant in enhancing the detection of different tissue types was tested experimentally. Users were asked to blindly insert a needle into artificial tissues with membranes at various depths under two force feedback conditions: (1) shaft and tip force together, and (2) only tip force. The ratio of successful to unsuccessful membrane detection was significantly higher when only the needle tip force is displayed to the user. The system proved to be compliant with the clinical applications requirements.

    View details for Web of Science ID 000298810002292

    View details for PubMedID 22255081

  • Robotic Needle Steering: Design, Modeling, Planning, and Image Guidance. In Surgical Robotics - Systems, Applications, and Visions. Cowan, N., J., Goldberg, K., Chirikjian, G., S., Fichtinger, G., Alterovitz, R., Reed, K., B., Okamura, A. M. edited by Rosen, J., Hannaford, B., Satava, R. Springer. 2011: 557-582
  • Task-Dependent Impedance Improves User Performance with a Virtual Prosthetic Arm 2011 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Blank, A., Okamura, A. M., Whitcomb, L. L. 2011: 2235-2242
  • Characterization of an Air Jet Haptic Lump Display 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Bianchi, M., Gwilliam, J. C., Degirmenci, A., Okamura, A. M. 2011: 3467-3470

    Abstract

    During manual palpation, clinicians rely on distributed tactile information to identify and localize hard lumps embedded in soft tissue. The development of tactile feedback systems to enhance palpation using robot-assisted minimally invasive surgery (RMIS) systems is challenging due to size and weight constraints, motivating a pneumatic actuation strategy. Recently, an air jet approach has been proposed for generating a lump percept. We use this technique to direct a thin stream of air through an aperture directly on the finger pad, which indents the skin in a hemispherical manner, producing a compelling lump percept. We hypothesize that the perceived parameters of the lump (e.g. size and stiffness) can be controlled by jointly adjusting air pressure and the aperture size through which air escapes. In this work, we investigate how these control variables interact to affect perceived pressure on the finger pad. First, we used a capacitive tactile sensor array to measure the effect of aperture size on output pressure, and found that peak output pressure increases with aperture size. Second, we performed a psychophysical experiment for each aperture size to determine the just noticeable difference (JND) of air pressure on the finger pad. Subject-averaged pressure JND values ranged from 19.4-24.7 kPa, with no statistical differences observed between aperture sizes. The aperture-pressure relationship and the pressure JND values will be fundamental for future display control.

    View details for Web of Science ID 000298810002297

    View details for PubMedID 22255086

  • Assessing the Quality of Force Feedback in Soft Tissue Simulation 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Basafa, E., Sefati, S., Okamura, A. M. 2011: 3451-3454

    Abstract

    Many types of deformable models have been proposed for simulation of soft tissue in surgical simulators, but their realism in comparison to actual tissue is rarely assessed. In this paper, a nonlinear mass-spring model is used for realtime simulation of deformable soft tissues and providing force feedback to a human operator. Force-deformation curves of real soft tissue samples were obtained experimentally, and the model was tuned accordingly. To test the realism of the model, we conducted two human-user experiments involving palpation with a rigid probe. First, in a discrimination test, users identified the correct category of real and virtual tissue better than chance, and tended to identify the tissues as real more often than virtual. Second, users identified real and virtual tissues by name, after training on only real tissues. The sorting accuracy was the same for both real and virtual tissues. These results indicate that, despite model limitations, the simulation could convey the feel of touching real tissues. This evaluation approach could be used to compare and validate various soft-tissue simulators.

    View details for Web of Science ID 000298810002293

    View details for PubMedID 22255082

  • Gradual anisometric-isometric transition for human-machine interfaces 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Gibo, T. L., Rotella, M. F., Bastian, A. J., Okamura, A. M. 2011: 4507-4510

    Abstract

    Human-machine interfaces (HMIs) are widely used in biomedical applications, from teleoperated surgical systems to rehabilitation devices. This paper investigates a method of control that allows an HMI to transition from anisometric to isometric mode, shifting the control input from position to force as the user's movement is gradually reduced. Two different approaches for achieving this transition are discussed: one is based on the natural system dynamics, whereas the other involves selecting and controlling dynamics. The two approaches were implemented on a custom haptic device in a targeting task. Anisometric to isometric transitioning can potentially be used for training purposes, enabling transfer of what was learned in one mode to the other, as well as novel studies of the human sensorimotor system.

    View details for Web of Science ID 000298810003208

    View details for PubMedID 22255340

  • Robot-Assisted Steerable Needles: Prototype Development and Feasibility Studies in an Animal Model. Vledder, Mark, G. Van, Majewicz, A., Marra, Steven, P., Song, Danny, Y., Okamura, Allison, M., Choti, M. A. 2011
  • Do Cerebellar Patients Generalize after Abrupt or Gradual Motor Learning? Gibo, T., L., Okamura, A., M., Bastian, A., J. 2011
  • Cerebellar predictions underlie the improvement of proprioceptive precision in active versus passive movements. Bhanpuri, N., Okamura, A., M., Bastian, A., J. 2011
  • Task-Dependent Impedance Improves User Performance with a Virtual Prosthetic Arm. Blank, A., Okamura, A., M., Whitcomb, L., L. 2011
  • Characterization of an Air Jet Haptic Lump Display. Bianchi, M., Gwilliam, J., C., Degirmenci, A., Okamura, A., M. 2011
  • Cutaneous Force Display via Shaped Contacts. Ludersdorfer, M., Damian, D., D., Arieta, A., Hernandez, Pfeifer, R., Okamura, A., M. 2011
  • Force Feedback and Sensory Substitution for Robot-Assisted Surgery. Surgical Robotics - Systems, Applications, and Visions Okamura, A., M., Verner, L., N., Yamamoto, T., Gwilliam, J., C., Griffiths, P., G. 2011: 419-448
  • Coaxial Needle Insertion Assistant for Epidural Puncture 2011 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS Koseki, Y., De Lorenzo, D., Chinzei, K., Okamura, A. M. 2011
  • Design and Evaluation of a Multi-Modal Haptic Skin Stimulation Apparatus 2011 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY (EMBC) Damian, D. D., Arieta, A. H., Okamura, A. M. 2011: 3455-3458

    Abstract

    Human grasping and manipulation are facilitated by cutaneous mechanoreceptors that provide information about contact location, pressure, and events such as making and breaking contact. A challenge in designing haptic feedback devices for the wearer of a prosthetic hand is simultaneous display of multiple types of haptic information. We present the preliminary design and evaluation of an apparatus for relaying multi-modal haptic information. The apparatus moves a set of contact points tangentially over the skin at a controlled speed, with controlled normal force. We apply this stimulus to an artificial skin instrumented with an embedded accelerometer, and characterize the resulting signals. Vibration frequency increases with applied normal force and tangential speed, whereas vibration amplitude increases with normal force and depends on skin properties. The results indicate that different forces and speeds can, under some conditions, be discriminated using vibration signals alone. Accurate identification of speeds is provided by series of vibration events that depend on the spatial distribution of contact points. This study motivates future work to perform human perception studies and create a wearable haptic display for prosthetics based on this concept.

    View details for Web of Science ID 000298810002294

    View details for PubMedID 22255083

  • Mechanics of Flexible Needles Robotically Steered through Soft Tissue INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Misra, S., REED, K. B., Schafer, B. W., Ramesh, K. T., Okamura, A. M. 2010; 29 (13): 1640-1660
  • Identifying the Role of Proprioception in Upper-Limb Prosthesis Control: Studies on Targeted Motion ACM TRANSACTIONS ON APPLIED PERCEPTION Blank, A., Okamura, A. M., Kuchenbecker, K. J. 2010; 7 (3)
  • Evaluation of Robotic Needle Steering in ex vivo Tissue 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Majewicz, A., Wedlick, T. R., Reed, K. B., Okamura, A. M. 2010: 2068-2073
  • Estimation of Model Parameters for Steerable Needles 2010 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA) Park, W., Reed, K. B., Okamura, A. M., Chirikjian, G. S. 2010: 3703-3708
  • Human vs. Robotic Tactile Sensing: Detecting Lumps in Soft Tissue. Gwilliam, J., Pezzementi, Z., Jantho, E., Okamura, A., M., Hsiao, S., S. 2010
  • Does a Basic Deficit in Force Control Underlie Cerebellar Ataxia? Charles, S., K., Okamura, A., M., Bastian, A., J. 2010
  • Design of a Haptic Simulator for Osteosynthesis Screw Insertion. Majewicz, A., Glasser, J., Bauer, R., Belkoff, S., Mears, S., Okamura, A., M. 2010
  • A Proposed Method for Correcting Coordination Deficits: Models and Simulation. Grow, D., I., Bhanpuri, N., H., Charles, S., K., Bastian, A., J., Okamura, A., M. 2010
  • Defining Performance Tradeoffs for Multi-Degree-of-Freedom Bilateral Teleoperators with LQG Control 49TH IEEE CONFERENCE ON DECISION AND CONTROL (CDC) Griffiths, P. G., Okamura, A. M. 2010: 3542-3547
  • Modelling of non-linear elastic tissues for surgical simulation COMPUTER METHODS IN BIOMECHANICS AND BIOMEDICAL ENGINEERING Misra, S., Ramesh, K. T., Okamura, A. M. 2010; 13 (6): 811-818

    Abstract

    Realistic modelling of the interaction between surgical instruments and human organs has been recognised as a key requirement in the development of high-fidelity surgical simulators. Primarily due to computational considerations, most of the past real-time surgical simulation research has assumed linear elastic behaviour for modelling tissues, even though human soft tissues generally possess non-linear properties. For a non-linear model, the well-known Poynting effect developed during shearing of the tissue results in normal forces not seen in a linear elastic model. Using constitutive equations of non-linear tissue models together with experiments, we show that the Poynting effect results in differences in force magnitude larger than the absolute human perception threshold for force discrimination in some tissues (e.g. myocardial tissues) but not in others (e.g. brain tissue simulants).

    View details for DOI 10.1080/10255840903505121

    View details for Web of Science ID 000285145800019

    View details for PubMedID 20503126

  • The Cerebellum Contributes to Constant and Dynamic Load Perception but not Position Perception. Bhanpuri, N., H., Okamura, A., M., Bastian, A., J. 2010
  • Defining Performance Tradeoffs for Multi-Degree-of-Freedom Bilateral Teleoperators with LQG Control. Griffiths, P., G., Okamura, A., M. 2010
  • Medical and Healthcare Robotics: Achievements and Opportunities IEEE Robotics and Automation Magazine Okamura, A., M., Mataric, M., J., Christensen, H., I. 2010; 3 (17): 26-37
  • Neural coding of lump detection in soft tissue. Gwilliam, J., C., Yoshioka, T., Okamura, A., M., Hsiao, S., S. 2010
  • Plugfest 2009: Global Interoperability in Telerobotics and Telemedicine. King, H., H., Hannaford, B., Kwok, K., W., Yang, G., Z., Griffiths, P., G., Okamura, A., M. 2010
  • Modeling of Nonlinear Elastic Tissues for Surgical Simulation. Computer Methods in Biomechanics and Biomedical Engineering Misra, S., Ramesh, K., T., Okamura, A., M. 2010; 6 (13): 811-818
  • Haptics for Robot-Assisted Minimally Invasive Surgery ROBOTICS RESEARCH Okamura, A. M., Verner, L. N., Reiley, C. E., Mahvash, M. 2010; 66: 361-372
  • Haptic Feedback: Technology and Medical Applications. Handbook of Touch. Okamura, A., M. 2010
  • Modeling and Control of Needles With Torsional Friction IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Reed, K. B., Okamura, A. M., Cowan, N. J. 2009; 56 (12): 2905-2916

    Abstract

    A flexible needle can be accurately steered by robotically controlling the bevel tip orientation as the needle is inserted into tissue. Friction between the long, flexible needle shaft and the tissue can cause a significant discrepancy between the orientation of the needle tip and the orientation of the base where the needle angle is controlled. Our experiments show that several common phantom tissues used in needle steering experiments impart substantial friction forces to the needle shaft, resulting in a lag of more than 45 ( degrees ) for a 10 cm insertion depth in some phantoms; clinical studies report torques large enough to cause similar errors during needle insertions. Such angle discrepancies will result in poor performance or failure of path planners and image-guided controllers, since the needles used in percutaneous procedures are too small for state-of-the-art imaging to accurately measure the tip angle. To compensate for the angle discrepancy, we develop an estimator using a mechanics-based model of the rotational dynamics of a needle being inserted into tissue. Compared to controllers that assume a rigid needle in a frictionless environment, our estimator-based controller improves the tip angle convergence time by nearly 50% and reduces the path deviation of the needle by 70%.

    View details for DOI 10.1109/TBME.2009.2029240

    View details for Web of Science ID 000272042400016

    View details for PubMedID 19695979

  • The importance of organ geometry and boundary constraints for planning of medical interventions MEDICAL ENGINEERING & PHYSICS Misra, S., Macura, K. J., Ramesh, K. T., Okamura, A. M. 2009; 31 (2): 195-206

    Abstract

    Realistic modeling of medical interventions involving tool-tissue interactions has been considered to be a key requirement in the development of high-fidelity simulators and planners. Organ geometry, soft-tissue constitutive laws, and boundary conditions imposed by the connective tissues surrounding the organ are some of the factors that govern the accuracy of medical intervention planning. In this study it is demonstrated that, for needle path planning, the organ geometry and boundary constraints surrounding the organ are the most important factors influencing the deformation. As an example, the procedure of needle insertion into the prostate (e.g. for biopsy or brachytherapy) is considered. Image segmentation is used to extract the anatomical details from magnetic resonance images, while object-oriented finite element analysis (OOF) software is used to generate finite element (FE) meshes from the segmented images. Two-dimensional FE simulations that account for complex anatomical details along with relative motion between the prostate and its surrounding structure using cohesive zone models are compared with traditional simulation models having simple organ geometry and boundary constraints. Nodal displacements for these simpler models were observed to be up to 14 times larger than those obtained from the anatomically accurate models.

    View details for DOI 10.1016/j.medengphy.2008.08.002

    View details for Web of Science ID 000263872200005

    View details for PubMedID 18815068

  • Controlling a Robotically Steered Needle in the Presence of Torsional Friction ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Reed, K. B., Okamura, A. M., Cowan, N. J. 2009: 3598-3603
  • Observations and Models for Needle-Tissue Interactions ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Misra, S., Reed, K. B., Schafer, B. W., Ramesh, K. T., Okamura, A. M. 2009: 3423-3428
  • Quantifying Perception of Nonlinear Elastic Tissue Models using Multidimensional Scaling WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Misra, S., Fuernstahl, P., Ramesh, K. T., Okamura, A. M., Harders, M. 2009: 570-575
  • Force & Torque Feedback vs Force Only Feedback WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Verner, L. N., Okamura, A. M. 2009: 406-410
  • Haptic feedback in robot-assisted minimally invasive surgery CURRENT OPINION IN UROLOGY Okamura, A. M. 2009; 19 (1): 102-107

    Abstract

    Robot-assisted minimally invasive surgery (RMIS) holds great promise for improving the accuracy and dexterity of a surgeon and minimizing trauma to the patient. However, widespread clinical success with RMIS has been marginal. It is hypothesized that the lack of haptic (force and tactile) feedback presented to the surgeon is a limiting factor. This review explains the technical challenges of creating haptic feedback for robot-assisted surgery and provides recent results that evaluate the effectiveness of haptic feedback in mock surgical tasks.Haptic feedback systems for RMIS are still under development and evaluation. Most provide only force feedback, with limited fidelity. The major challenge at this time is sensing forces applied to the patient. A few tactile feedback systems for RMIS have been created, but their practicality for clinical implementation needs to be shown. It is particularly difficult to sense and display spatially distributed tactile information. The cost-benefit ratio for haptic feedback in RMIS has not been established.The designs of existing commercial RMIS systems are not conducive for force feedback, and creative solutions are needed to create compelling tactile feedback systems. Surgeons, engineers, and neuroscientists should work together to develop effective solutions for haptic feedback in RMIS.

    View details for DOI 10.1097/MOU.0b013e32831a478c

    View details for Web of Science ID 000262215600020

    View details for PubMedID 19057225

  • Feedback Control for Steering Needles through 3D Deformable Tissue using Helical Paths. Robotics: Science and Systems. Hauser, K., Alterovitz, R., Chentanez, N., Okamura, A., Goldberg, K. 2009
  • Observations of Needle-Tissue Interactions 2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20 Misra, S., Reed, K. B., Ramesh, K. T., Okamura, A. M. 2009: 262-265

    Abstract

    Needles with asymmetric bevel tips naturally bend when they are inserted into soft tissue. In this study, we present an analytical model for the loads developed at the bevel tip during needle-tissue interaction. The model calculates the loads based on the geometry of the bevel edge and gel material properties. The modeled transverse force developed at the tip is compared to forces measured experimentally. The analytical model explains the trends observed in the experiments. In addition to macroscopic studies, we also present microscopic observations of needle-tissue interactions. These results contribute to a mechanics-based model of robotic needle steering, extending previous work on kinematic models.

    View details for Web of Science ID 000280543600070

    View details for PubMedID 19963709

  • Design Considerations and Human-Machine Performance of Moving Virtual Fixtures ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Gibo, T. L., Verner, L. N., Yuh, D. D., Okamura, A. M. 2009: 2958-2963
  • Haptics as an Aid to Copying for People with Williams Syndrome WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Lee, J., Okamura, A. M., Landau, B. 2009: 356-361
  • Stiffness Discrimination with Visual and Proprioceptive Cues. Gurari, N., Kuchenbecker, K., J., Okamura, A., M. 2009
  • Can Cerebellar Dysmetria be Explained by an Incorrect Internal Model of Limb Dynamics? Bhanpuri, N., H., Grow, D., I., Okamura, A., M., Bastian, A., J. 2009
  • Modeling and Control of Needles with Torsional Friction. IEEE Transactions on Biomedical Engineering Reed, K., B., Okamura, A., M., Cowan, N., J. 2009; 12 (56): 2905-2916
  • Environment Discrimination with Vibration Feedback to the Foot, Arm, and Fingertip 2009 IEEE 11TH INTERNATIONAL CONFERENCE ON REHABILITATION ROBOTICS, VOLS 1 AND 2 Gurari, N., Smith, K., Madhav, M., Okamura, A. M. 2009: 398-403
  • Tissue Property Estimation and Graphical Display for Teleoperated Robot-Assisted Surgery ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Yamamoto, T., Vagvolgyi, B., Balaji, K., Whitcomb, L. L., Okamura, A. M. 2009: 3117-3123
  • Effects of Haptic and Graphical Force Feedback on Teleoperated Palpation ICRA: 2009 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-7 Gwilliam, J. C., Mahvash, M., Vagvolgyi, B., Vacharat, A., Yuh, D. D., Okamura, A. M. 2009: 3315-3320
  • Quantification and Reproduction of Human Hand Skin Stretch and its Effects on Proprioception. Greenwald, E., Pompe, J., Hsiao, S., Okamura, A. 2009
  • Characterization of Pre-Curved Needles for Steering in Tissue 2009 ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-20 Wedlick, T. R., Okamura, A. M. 2009: 1200-1203

    Abstract

    Needles with tip asymmetry deflect upon insertion into soft tissue, an effect that can be used to steer needles within the body. This paper presents a phenomenological characterization of the steering behavior of pre-curved needles, which have tip asymmetry due to curvature of the needle near the tip. We describe needle construction methods and a needle shaft triangulation algorithm to compute the shape of the needle based on images. Experimental results show that pre-curved needles possess greater dexterity than bevel-tipped needles and achieve radii of curvature similar to pre-bent needles. For long pre-curve arc lengths, the radius of curvature of the needle was found to approach the radius of curvature of the pre-curve. Pre-curved needles were found to display behaviors not seen with bevel-tipped needles, such as the insertion velocity influencing the path of the tip within the tissue and the ability to plastically deform the needle during steering.

    View details for Web of Science ID 000280543601032

    View details for PubMedID 19963994

  • Stiffness Discrimination with Visual and Proprioceptive Cues WORLD HAPTICS 2009: THIRD JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Gurari, N., Kuchenbecker, K. J., Okamura, A. M. 2009: 121-126
  • Surgical and Interventional Robotics: Part III Surgical Assistance Systems IEEE ROBOTICS & AUTOMATION MAGAZINE Hager, G. D., Okamura, A. M., Kazanzides, P., Whitcomb, L. L., Fichtinger, G., Taylor, R. H. 2008; 15 (4): 84-93
  • Modeling of tool-tissue interactions for computer-based surgical simulation: A literature review PRESENCE-TELEOPERATORS AND VIRTUAL ENVIRONMENTS Misra, S., Ramesh, K. T., Okamura, A. M. 2008; 17 (5): 463-491
  • Surgical and interventional robotics: Part II - Surgical CAD-CAM systems IEEE ROBOTICS & AUTOMATION MAGAZINE Fichtinger, G., Kazanzides, P., Okamura, A. M., Hager, G. D., Whitcomb, L. L., Taylor, R. H. 2008; 15 (3): 94-102
  • Surgical and interventional robotics - Core concepts, technology, and design IEEE ROBOTICS & AUTOMATION MAGAZINE Kazanzides, P., Fichtinger, G., Hager, G. D., Okamura, A. M., Whitcomb, L. L., Taylor, R. H. 2008; 15 (2): 122-130
  • Modeling the forces of cutting with scissors IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Mahvash, M., Voo, L. M., Kim, D., Jeung, K., Wainer, J., Okamura, A. M. 2008; 55 (3): 848-856

    Abstract

    Modeling forces applied to scissors during cutting of biological materials is useful for surgical simulation. Previous approaches to haptic display of scissor cutting are based on recording and replaying measured data. This paper presents an analytical model based on the concepts of contact mechanics and fracture mechanics to calculate forces applied to scissors during cutting of a slab of material. The model considers the process of cutting as a sequence of deformation and fracture phases. During deformation phases, forces applied to the scissors are calculated from a torque-angle response model synthesized from measurement data multiplied by a ratio that depends on the position of the cutting crack edge and the curve of the blades. Using the principle of conservation of energy, the forces of fracture are related to the fracture toughness of the material and the geometry of the blades of the scissors. The forces applied to scissors generally include high-frequency fluctuations. We show that the analytical model accurately predicts the average applied force. The cutting model is computationally efficient, so it can be used for real-time computations such as haptic rendering. Experimental results from cutting samples of paper, plastic, cloth, and chicken skin confirm the model, and the model is rendered in a haptic virtual environment.

    View details for DOI 10.1109/TBME.2007.908069

    View details for Web of Science ID 000253733800001

    View details for PubMedID 18334376

  • Haptic simulation of elbow joint spasticity SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Grow, D. I., Wu, M. (., Locastro, M. J., Arora, S. K., Bastian, A. J., Okamura, A. M. 2008: 475-476
  • The touch thimble: Providing fingertip contact feedback during point-force haptic interaction SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Kuchenbecker, K. J., Ferguson, D., Kutzer, M., Moses, M., Okamura, A. M. 2008: 239-246
  • A Simulator to Explore the Role of Haptic Feedback in Cataract Surgery Training MEDICINE MEETS VIRTUAL REALITY 16 Doyle, L., Gauthier, N., Ramanathan, S., Okamura, A. 2008; 132: 106-111

    Abstract

    Phacoemulsification cataract surgery, a minimally invasive technique to remove a cloudy lens from the eye, is one of the most commonly performed surgical procedures in the western world. Conventional training for this procedure involves didactic lectures and practice on pig and human cadaver eyes, none of which allow trainees to form an accurate predictive model of human tissue behavior during surgery. A virtual environment simulator for capsulorrhexis, one of the first steps in cataract surgery, has been developed that allows a trainee to use surgical instruments to excise a circle of tissue on the anterior side of the lens capsule through tearing. The simulator invokes a deformable mass-spring-damper mesh model of the tissue that can be grasped and torn via shearing. A novel algorithm for mesh division and maintenance enables realistic tearing behavior. The trainee controls tool motion using a 3-degree-of-freedom haptic device, and haptic feedback is provided from the virtual tissue. Although the haptic feedback in a real capsulorrhexis procedure is below the human threshold of haptic sensing, this simulator enables an experiment to determine the effectiveness of "haptic training wheels" -- the idea of haptic training for a task without haptic feedback.

    View details for Web of Science ID 000272668400023

    View details for PubMedID 18391267

  • Measurement-Based Modeling for Haptic Display. In Haptic Rendering: Foundations, Algorithms, and Applications. Okamura, A., M., Kuchenbecker, K., J., Mahvash, M. edited by Lin, M., C., Otaduy, M. AK Peters.. 2008: 1
  • Control Methods for Guidance Virtual Fixtures in Compliant Human-Machine Interfaces 2008 IEEE/RSJ INTERNATIONAL CONFERENCE ON ROBOTS AND INTELLIGENT SYSTEMS, VOLS 1-3, CONFERENCE PROCEEDINGS Marayong, P., Hager, G. D., Okamura, A. M. 2008: 1166-1172
  • Chapter 30: Haptics. In Springer Handbook of Robotics Hannaford, B., Okamura, A., M. Springer. 2008: 719-739
  • Force-feedback surgical teleoperator: Controller design and palpation experiments SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Mahvash, M., Gwilliam, J., Agarwal, R., Vagvolgyi, B., Su, L., Yuh, D. D., Okamura, A. M. 2008: 465-471
  • A Simulator to Explore the Role of Haptic Feedback in Cataract Surgery Training. Medicine Meets Virtual Reality. Doyle, L., Gauthier, N., Ramanathan, S., Okamura, A., M. 2008
  • Needle-Tissue Interaction Forces for Bevel-Tip Steerable Needles 2008 2ND IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB 2008), VOLS 1 AND 2 Misra, S., Reed, K. B., Douglas, A. S., Ramesh, K. T., Okamura, A. M. 2008: 224-231
  • Effects of visual force feedback on robot-assisted surgical task performance JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY Reiley, C. E., Akinbiyi, T., Burschka, D., Chang, D. C., Okamura, A. M., Yuh, D. D. 2008; 135 (1): 196-202

    Abstract

    Direct haptic (force or tactile) feedback is negligible in current surgical robotic systems. The relevance of haptic feedback in robot-assisted performances of surgical tasks is controversial. We studied the effects of visual force feedback, a haptic feedback surrogate, on tying surgical knots with fine sutures similar to those used in cardiovascular surgery.By using a modified da Vinci robotic system (Intuitive Surgical, Inc, Sunnyvale, Calif) equipped with force-sensing instrument tips and real-time visual force feedback overlays in the console image, 10 surgeons each tied 10 knots with and 10 knots without visual force feedback. Four surgeons had significant prior da Vinci experience, and the remaining 6 surgeons did not. Performance parameters, including suture breakage and secure knots, peak and standard deviation of applied forces, and completion times using 5-0 silk sutures, were recorded. Chi-square and Student t test analyses determined the differences between groups.Among surgeon subjects with robotic experience, no differences in measured performance parameters were found between robot-assisted knot ties executed with and without visual force feedback. Among surgeons without robotic experience, however, visual force feedback was associated with lower suture breakage rates, peak applied forces, and standard deviations of applied forces. Visual force feedback did not impart differences in knot completion times or loose knots for either surgeon group.Visual force feedback resulted in reduced suture breakage, lower forces, and decreased force inconsistencies among novice robotic surgeons, although elapsed time and knot quality were unaffected. In contrast, visual force feedback did not affect these metrics among surgeons experienced with the da Vinci system. These results suggest that visual force feedback primarily benefits novice robot-assisted surgeons, with diminishing benefits among experienced surgeons.

    View details for DOI 10.1016/j.jtcvs.2007.08.043

    View details for Web of Science ID 000252139600029

    View details for PubMedID 18179942

  • Techniques for Environment Parameter Estimation During Telemanipulation 2008 2ND IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB 2008), VOLS 1 AND 2 Yamamoto, T., Bernhardt, M., Peer, A., Buss, M., Okamura, A. M. 2008: 217-223
  • Effects of proprioceptive motion feedback on sighted and non-sighted control of a virtual hand prosthesis SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Blank, A., Okamura, A. M., Kuchenbecker, K. J. 2008: 141-142
  • Modeling realistic tool-tissue interactions with haptic feedback: A learning-based method SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2008, PROCEEDINGS Pezzernenti, Z., Ursu, D., Misra, S., Okamura, A. M. 2008: 209-215
  • Compensating for Torsion Windup in Steerable Needles. Okamura, A., M., Reed, K., B. 2008
  • The Touch Thimble: Providing Fingertip Contact Feedback During Point-Force Haptic Interaction. Kuchenbecker, K., J., Ferguson, D., Kutzer, M., Moses, M., Okamura, A., M. 2008
  • Telemanipulators with Sensor/Actuator Asymmetries Fail the Robustness Criterion. Verner, L., N., Okamura, A., M. 2008
  • Multi-Estimator Technique for Environment Parameter Estimation During Telemanipulation. Yamamoto, T., Bernhardt, M., Peer, A., Buss, M., Okamura, A., M. 2008
  • Physically Valid Surgical Simulators: Linear Versus Nonlinear Tissue Models MEDICINE MEETS VIRTUAL REALITY 16 Misra, S., Ramesh, K. T., Okamura, A. M. 2008; 132: 293-295

    Abstract

    Realistic modeling of the interaction between surgical instruments and organs has been recognized as a key requirement in the development of high-fidelity surgical simulators. For a nonlinear model, the well-known Poynting effect developed during shearing of the tissue results in normal forces not seen in a linear elastic model. It is demonstrated that the difference in force magnitude for myocardial tissue is larger than the just noticeable difference for contact force discrimination thresholds published in the psychophysics literature. This work also proposes the validation of simulators by careful examination of relevant simulator design parameters that relate to final simulator behaviors affecting clinical outcomes.

    View details for Web of Science ID 000272668400063

    View details for PubMedID 18391307

  • Control Methods for Guidance Virtual Fixtures in Compliant Human-Machine Interfaces. Marayong, P., Hager, G., D., Okamura, A., M. 2008
  • Integrated Planning and Image-Guided Control for Planar Needle Steering 2008 2ND IEEE RAS & EMBS INTERNATIONAL CONFERENCE ON BIOMEDICAL ROBOTICS AND BIOMECHATRONICS (BIOROB 2008), VOLS 1 AND 2 Reed, K. B., Kallem, V., Alterovitz, R., Goldberg, K., Okamura, A. M., Cowan, N. J. 2008: 907-912
  • Friction compensation for enhancing transparency of a teleoperator with compliant transmission IEEE TRANSACTIONS ON ROBOTICS Mahvash, M., Okamura, A. 2007; 23 (6): 1240-1246
  • Pseudo-admittance bilateral telemanipulation with guidance virtual fixtures INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Abbott, J. J., Okamura, A. M. 2007; 26 (8): 865-884
  • Human performance in a knob-turning task WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Gurari, N., Okamura, A. M. 2007: 96-101
  • Teleoperation of steerable needles PROCEEDINGS OF THE 2007 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-10 Romano, J. M., Webster, R. J., Okamura, A. M. 2007: 934-939
  • Force feedback is noticeably different for linear versus nonlinear elastic tissue models WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Misra, S., Okamura, A. M., Ramesh, K. T. 2007: 519-524
  • Virtual fixture control for compliant human-machine interfaces PROCEEDINGS OF THE 2007 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-10 Marayong, P., Na, H. S., Okamura, A. M. 2007: 4018-4024
  • Effects of translational and gripping force feedback are decoupled in a 4-degree-of-freedom telemanipulator WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Verner, L. N., Okamura, A. M. 2007: 286-291
  • Enhancing transparency of a posit ion-exchange teleoperator WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Mahvash, M., Okamura, A. M. 2007: 470-475
  • Evaluation of human performance with kinematic and haptic errors WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Yamamoto, T., Okamura, A. M. 2007: 78-83
  • Dynamic guidance with pseudoadmittance virtual fixtures PROCEEDINGS OF THE 2007 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-10 Pezzementi, Z., Okamura, A. M., Hager, G. D. 2007: 1761-1767
  • Haptic virtual fixtures for robot-assisted manipulation ROBOTICS RESEARCH Abbott, J. J., Marayong, P., Okamura, A. M. 2007; 28: 49-64
  • Design of a Pill-Sized 12-legged Endoscopic Capsule Robot. Okamura, A., M., Quirini, M., Webster III, R., J., Menciassi, A., Dario, P. 2007
  • Force Sensing in Robot-Assisted Surgery: Which Degrees of Freedom are Most Important? Medicine Meets Virtual Reality (MMVR) 15. Saha, S., Mahvash, M., Verner, L., N., Okamura, A., M. 2007
  • Educational Haptics. Grow, D., I., Verner, L., N., Okamura, A., M. 2007
  • Electrolytic Silicone Bourdon Tube Microactuator for Reconfigurable Surgical Robots. Okamura, A., M., Pak, N., Ng, Webster III, R., J., Menciassi, A., Dario, P. 2007
  • Friction Compensation for Enhancing Transparency of a Teleoperator with Compliant Transmission. IEEE Transactions on Robotics Mahvash, M., Okamura, A., M. 2007; 6 (23): 1240-1246
  • Quantifying the value of visual and haptic position feedback during force-based motion control WORLD HAPTICS 2007: SECOND JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Kuchenbecker, K. J., Gurari, N., Okamura, A. M. 2007: 561-562
  • Effects of visual and proprioceptive motion feedback on human control of targeted movement 2007 IEEE 10TH INTERNATIONAL CONFERENCE ON REHABILITATION ROBOTICS, VOLS 1 AND 2 Kuchenbecker, K. J., Gurari, N., Okamura, A. M. 2007: 513-524
  • Nonholonomic modeling of needle steering INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Webster, R. J., Kim, J. S., Cowan, N. J., Chirikjian, G. S., Okamura, A. M. 2006; 25 (5-6): 509-525
  • Stable forbidden-region virtual fixtures for bilateral telemanipulation JOURNAL OF DYNAMIC SYSTEMS MEASUREMENT AND CONTROL-TRANSACTIONS OF THE ASME Abbott, J. J., Okamura, A. M. 2006; 128 (1): 53-64

    View details for DOI 10.1115/1.2168163

    View details for Web of Science ID 000236439100007

  • Nonholonomic modeling of needle steering EXPERIMENTAL ROBOTICS IX Iii, R. J., Cowan, N. J., Chirikjian, G., Okamura, A. M. 2006; 21: 35-44
  • Dynamic augmented reality for sensory substitution in robot-assisted surgical systems. Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference Akinbiyi, T., Reiley, C. E., Saha, S., Burschka, D., Hasser, C. J., Yuh, D. D., Okamura, A. M. 2006; 1: 567-570

    Abstract

    Teleoperated robot-assisted surgical systems provide surgeons with improved precision, dexterity, and visualization over traditional minimally invasive surgery. The addition of haptic (force and/or tactile) feedback has been proposed as a way to further enhance the performance of these systems. However, due to limitations in sensing and control technologies, implementing direct haptic feedback to the surgeon's hands remains impractical for clinical application. A new, intuitive augmented reality system for presentation of force information through sensory substitution has been developed and evaluated. The augmented reality system consists of force-sensing robotic instruments, a kinematic tool tracker, and a graphic display that overlays a visual representation of force levels on top of the moving instrument tips. The system is integrated with the da Vinci Surgical System (Intuitive Surgical, Inc.) and tested by several users in a phantom knot tying task. The augmented reality system decreases the number of broken sutures, decreases the number of loose knots, and results in more consistent application of forces.

    View details for PubMedID 17945986

  • Effect of hand dynamics on virtual fixtures for compliant human-machine interfaces* SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Marayong, P., Hager, G. D., Okamura, A. M. 2006: 109-115
  • Object Capture With a Camera-Mobile Robot System: An Introductory Robotics Project. IEEE Robotics and Automation Magazine Okamura, A., M., Webster III, R., J. 2006; 1 (13): 85-88
  • Pseudo-admittance bilateral telemanipulation with guidance virtual fixtures SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Abbott, J. J., Okamura, A. M. 2006: 169-175
  • Sensor/Actuator asymmetries in telemanipulators: Implications of partial force feedback SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Verner, L. N., Okamura, A. M. 2006: 309-314
  • Toward active cannulas: Miniature snake-like surgical robots 2006 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-12 Webster, R. J., Okamura, A. M., Cowan, N. J. 2006: 2857-2863
  • Portability and applicability of virtual fixtures across medical and manufacturing tasks 2006 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-10 Lin, H. C., Mills, K., Kazanzides, P., Hager, G. D., Marayong, P., Okamura, A. M., Karam, R. 2006: 225-230
  • Dynamic augmented reality for sensory substitution in robot-assisted surgical systems 2006 28TH ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY, VOLS 1-15 Akinbiyi, T., Reiley, C. E., Saha, S., Burschka, D., Hasser, C. J., Yuh, D. D., Okamura, A. M. 2006: 3090-3093
  • Friction compensation for a force-feedback telerobotic system 2006 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-10 Mahvash, M., Okamura, A. M. 2006: 3268-3273
  • Friction compensation for a force-feedback teleoperator with compliant transmission PROCEEDINGS OF THE 45TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-14 Mahvash, M., Okamura, A. M. 2006: 4508-4513
  • Effects of Haptic Feedback on Exploration. Wu, M., Okamura, A., M. 2006
  • Environment parameter estimation during bilateral telemanipulation SYMPOSIUM ON HAPTICS INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS 2006, PROCEEDINGS Misra, S., Okamura, A. M. 2006: 301-307
  • Effects of position quantization and sampling rate on virtual-wall passivity IEEE TRANSACTIONS ON ROBOTICS Abbott, J. J., Okamura, A. M. 2005; 21 (5): 952-964
  • Human-machine collaborative systems for microsurgical applications INTERNATIONAL JOURNAL OF ROBOTICS RESEARCH Kragic, D., Marayong, P., Li, M., Okamura, A. M., Hager, G. A. 2005; 24 (9): 731-741
  • Transrectal fiducial carrier for radiographic image registration in prostate Brachytherapy Kemper, J., Burkholder, A., Jain, A., Mustufa, T., Wyrobek, K., Burdette, C., Song, D., Okamura, A., Fichtinger, G. AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS. 2005: 2108-2108
  • Effect of sensory substitution on suture-manipulation forces for robotic surgical systems JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY Kitagawa, M., Dokko, D., Okamura, A. M., Yuh, D. D. 2005; 129 (1): 151-158

    Abstract

    Direct haptic (force or tactile) feedback is not yet available in commercial robotic surgical systems. Previous work by our group and others suggests that haptic feedback might significantly enhance the execution of surgical tasks requiring fine suture manipulation, specifically those encountered in cardiothoracic surgery. We studied the effects of substituting direct haptic feedback with visual and auditory cues to provide the operating surgeon with a representation of the forces he or she is applying with robotic telemanipulators.Using the robotic da Vinci surgical system (Intuitive Surgical, Inc, Sunnyvale, Calif), we compared applied forces during a standardized surgical knot-tying task under 4 different sensory-substitution scenarios: no feedback, auditory feedback, visual feedback, and combined auditory-visual feedback.The forces applied with these sensory-substitution modes more closely approximate suture tensions achieved under ideal haptic conditions (ie, hand ties) than forces applied without such sensory feedback. The consistency of applied forces during robot-assisted suture tying aided by visual feedback or combined auditory-visual feedback sensory substitution is superior to that achieved with hand ties. Robot-assisted ties aided with auditory feedback revealed levels of consistency that were generally equivalent or superior to those attained with hand ties. Visual feedback and auditory feedback improve the consistency of robotically applied forces.Sensory substitution, in the form of visual feedback, auditory feedback, or both, confers quantifiable advantages in applied force accuracy and consistency during the performance of a simple surgical task.

    View details for DOI 10.1016/j.jtcvs.2004.05.029

    View details for Web of Science ID 000226216600021

    View details for PubMedID 15632837

  • A velocity-dependent model for needle insertion in soft tissue. Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention Crouch, J. R., Schneider, C. M., Wainer, J., Okamura, A. M. 2005; 8: 624-632

    Abstract

    Models that predict the soft tissue deformation caused by needle insertion could improve the accuracy of procedures such as brachytherapy and needle biopsy. Prior work on needle insertion modeling has focused on static deformation; the experiments presented here show that dynamic effects such as relaxation are important. An experimental setup is described for recording and measuring the deformation that occurs with needle insertion into a soft tissue phantom. Analysis of the collected data demonstrates the time- and velocity-dependent nature of the deformation. Deformation during insertion is shown to be well represented using a velocity-dependent force function with a linear elastic finite element model. The model's accuracy is limited to the period during needle motion, indicating that a viscoelastic tissue model may be required to capture tissue relaxation after the needle stops.

    View details for PubMedID 16686012

  • Human-machine collaborative systems for microsurgical applications ROBOTICS RESEARCH Kragic, D., Marayong, P., Li, M., Okamura, A. M., Hager, G. D. 2005; 15: 162-171
  • Planning for steerable bevel-tip needle insertion through 2D soft tissue with obstacles 2005 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-4 Alterovitz, R., Goldberg, K., Okamura, A. 2005: 1640-1645
  • Automatic detection and segmentation of robot-assisted surgical motions. Medical image computing and computer-assisted intervention : MICCAI ... International Conference on Medical Image Computing and Computer-Assisted Intervention Lin, H. C., Shafran, I., Murphy, T. E., Okamura, A. M., Yuh, D. D., Hager, G. D. 2005; 8: 802-810

    Abstract

    Robotic surgical systems such as Intuitive Surgical's da Vinci system provide a rich source of motion and video data from surgical procedures. In principle, this data can be used to evaluate surgical skill, provide surgical training feedback, or document essential aspects of a procedure. If processed online, the data can be used to provide context-specific information or motion enhancements to the surgeon. However, in every case, the key step is to relate recorded motion data to a model of the procedure being performed. This paper examines our progress at developing techniques for "parsing" raw motion data from a surgical task into a labelled sequence of surgical gestures. Our current techniques have achieved >90% fully automated recognition rates on 15 datasets.

    View details for PubMedID 16685920

  • A fracture mechanics approach to haptic synthesis of tissue cutting with scissors WORLD HAPTICS CONFERENCE: FIRST JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRUTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Mahvash, M., Okamura, A. M. 2005: 356-362
  • Steering flexible needles under Markov motion uncertainty 2005 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Alterovitz, R., Lim, A., Goldberg, K., Chirikjian, G. S., Okamura, A. M. 2005: 120-125
  • Design considerations for robotic needle steering 2005 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-4 Webster, R. J., Memisevic, J., Okamura, A. M. 2005: 3588-3594
  • Effects of velocity on human force control WORLD HAPTICS CONFERENCE: FIRST JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRUTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Wu, M., Abbott, J. J., Okamura, A. M. 2005: 73-79
  • A velocity-dependent model for needle insertion in soft tissue MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2005, PT 2 Crouch, J. R., Schneider, C. M., Wainer, J., Okamura, A. M. 2005; 3750: 624-632
  • Diffusion-based motion planning for a nonholonomic flexible needle model 2005 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION (ICRA), VOLS 1-4 Park, W., Kim, J. S., Zhou, Y., Cowan, N. J., Okamura, A. M., Chirikjian, G. S. 2005: 4600-4605
  • Effects of gripping and translational forces on teleoperation MULTI-POINT INTERACTION WITH REAL AND VIRTUAL OBJECTS Verner, L. N., Jeung, K. A., Okamura, A. M. 2005; 18: 231-241
  • The snaptic paddle: A modular haptic device WORLD HAPTICS CONFERENCE: FIRST JOINT EUROHAPTICS CONFERENCE AND SYMPOSIUM ON HAPTIC INTERFACES FOR VIRUTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Wong, C. E., Okamura, A. M. 2005: 537-538
  • Automatic detection and segmentation of robot-assisted surgical motions MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2005, PT 1 Lin, H. C., Shafran, I., Murphy, T. E., Okamura, A. M., Yuh, D. D., Hager, G. D. 2005; 3749: 802-810
  • Vision-assisted control for manipulation using virtual fixtures IEEE TRANSACTIONS ON ROBOTICS AND AUTOMATION Bettini, A., Marayong, P., Lang, S., Okamura, A. M., Hager, G. D. 2004; 20 (6): 953-966
  • Force modeling for needle insertion into soft tissue IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING Okamura, A. M., Simone, C., O'Leary, M. D. 2004; 51 (10): 1707-1716

    Abstract

    The modeling of forces during needle insertion into soft tissue is important for accurate surgical simulation, preoperative planning, and intelligent robotic assistance for percutaneous therapies. We present a force model for needle insertion and experimental procedures for acquiring data from ex vivo tissue to populate that model. Data were collected from bovine livers using a one-degree-of-freedom robot equipped with a load cell and needle attachment. computed tomography imaging was used to segment the needle insertion process into phases identifying different relative velocities between the needle and tissue. The data were measured and modeled in three parts: 1) capsule stiffness, a nonlinear spring model; 2) friction, a modified Karnopp model; and 3) cutting, a constant for a given tissue. In addition, we characterized the effects of needle diameter and tip type on insertion force using a silicone rubber phantom. In comparison to triangular and diamond tips, a bevel tip causes more needle bending and is more easily affected by tissue density variations. Forces for larger diameter needles are higher due to increased cutting and friction forces.

    View details for DOI 10.1109/TBME.2004.831542

    View details for Web of Science ID 000224001900002

    View details for PubMedID 15490818

  • Speed-accuracy characteristics of human-machine cooperative manipulation using virtual fixtures with variable admittance HUMAN FACTORS Marayong, P., Okamura, A. M. 2004; 46 (3): 518-532

    Abstract

    This work explores the effect of virtual fixture admittance on the performance, defined by error and time, of task execution with a human-machine cooperative system. A desired path is obtained using computer vision, and virtual fixtures for assistance in planar path following were implemented on an admittance-controlled robot. The admittance controller uses a velocity gain, so that the speed of the robot is proportional to the force applied by the operator. The level of virtual fixture guidance is determined by the admittance ratio, which is the ratio of the admittance gain of the force components orthogonal to the path to the gain of the force components parallel to the path. In Experiment 1, we found a linear relationship between admittance ratio and performance. In Experiment 2, we examined the effect of admittance ratio on the performance of three tasks: path following, off-path targeting, and obstacle avoidance. An algorithm was developed to select an appropriate admittance ratio based on the nature of the task. Automatic admittance ratio tuning is recommended for next-generation virtual fixtures. Actual or potential applications of this research include surgery, assembly, and manipulation at the macro and micro scales.

    View details for Web of Science ID 000224978900011

    View details for PubMedID 15573549

  • Application of haptic feedback to robotic surgery JOURNAL OF LAPAROENDOSCOPIC & ADVANCED SURGICAL TECHNIQUES-PART A Bethea, B. T., Okamura, A. M., Kitagawa, M., Fitton, T. P., Cattaneo, S. M., Gott, V. L., Baumgartner, W. A., Yuh, D. D. 2004; 14 (3): 191-195

    Abstract

    Robotic surgical systems have greatly contributed to the advancement of minimally invasive endoscopic surgery. However, current robotic systems do not provide tactile or haptic feedback to the operating surgeon. Under certain circumstances, particularly with the manipulation of delicate tissues and suture materials, this may prove to be a significant irritation. We hypothesize that haptic feedback, in the form of sensory substitution, facilitates the performance of surgical knot tying. This preliminary study describes evidence that visual sensory substitution permits the surgeon to apply more consistent, precise, and greater tensions to fine suture materials without breakage during robot-assisted knot tying.

    View details for Web of Science ID 000222276000015

    View details for PubMedID 15245675

  • Teleoperation with sensor/actuator asymmetry: Task performance with partial force feedback 12TH INTERNATIONAL SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Semere, W., Kitagawa, M., Okamura, A. M. 2004: 121-127
  • Haptic rendering of tissue cutting with scissors MEDICINE MEETS VIRTUAL REALITY 12 Weiss, D. J., Okamura, A. M. 2004; 98: 407-409

    Abstract

    Current surgical simulations that involve cutting with scissors lack display of forces "between the fingers" of the operator. The objective of this work is to develop a fast, realistic haptic rendering technique for scissor cutting that can be easily integrated into soft tissue models commonly used in surgical simulators. A virtual environment was created for combined graphic and haptic display of cutting. Two 2-dimensional deformable mass-spring-damper models were developed: The first is a large mesh that is used to calculate translational forces. The second is a smaller, one-element-thick mesh that is used to calculate cutting (angular) forces. This technique was implemented on the haptic scissors, a haptic interface that allows motion and force feedback in translation and cutting.

    View details for Web of Science ID 000222326200090

    View details for PubMedID 15544316

  • The effect of visual and haptic feedback on computer-assisted needle insertion. Computer aided surgery Gerovich, O., Marayong, P., Okamura, A. M. 2004; 9 (6): 243-249

    Abstract

    We present a study evaluating the effects of visual and haptic feedback on human performance in a needle insertion task.A one-degree-of-freedom needle insertion simulator with a three-layer tissue model (skin, fat and muscle) was used in perceptual experiments. The objective of the 14 subjects was to detect the puncture of each tissue layer using varying haptic and visual cues. Performance was measured by overshoot error-the distance traveled by the virtual needle after puncture.Without force feedback, real-time visual feedback reduced error by at least 87% in comparison to static image overlay. Force feedback, in comparison to no force feedback, reduced puncture overshoot by at least 52% when visual feedback was absent or limited to static image overlay. A combination of force and visual feedback improved performance, especially for tissues with low stiffness, by at least 43% with visual display of the needle position, and by at least 67% with visual display of layer deflection.Real-time image overlay significantly enhances controlled puncture during needle insertion. Force feedback may not be necessary except in circumstances where visual feedback is limited.

    View details for PubMedID 16112974

  • Performance analysis of steady-hand teleoperation versus cooperative manipulation 12TH INTERNATIONAL SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Emeagwali, I., Marayong, P., Abbott, J. J., Okamura, A. M. 2004: 316-322
  • Vision-based assistance for ophthalmic micro-surgery MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2004, PT 2, PROCEEDINGS Dewan, M., Marayong, P., Okamura, A. M., Hager, G. D. 2004; 3217: 49-57
  • Effect of sensory substitution on suture manipulation forces for surgical teleoperation MEDICINE MEETS VIRTUAL REALITY 12 Kitagawa, M., Dokko, D., Okamura, A. M., Bethea, B. T., Yuh, D. D. 2004; 98: 157-163

    Abstract

    Bilateral telemanipulation, which applies haptic feedback to the operator, is not yet available in most commercial robot-assisted surgical systems. We have shown in previous work that the lack of haptic (force or tactile) feedback is detrimental in applications requiring fine suture manipulation. In this paper, we study the effect of substituting direct haptic feedback with visual and auditory cues. Using the da Vinci robot from Intuitive Surgical, we observed the difference between applied forces during a knot tying procedure for four different sensory feedback substitution scenarios: no feedback, auditory feedback, visual feedback, and a combination of auditory and visual feedback. Our results indicate that visual feedback, which provides continuous force information, would improve robot-assisted performance during complex surgical tasks such as knot tying with fine sutures. Discrete auditory feedback gives additional useful support to the surgeon.

    View details for Web of Science ID 000222326200037

    View details for PubMedID 15544263

  • Methods for haptic feedback in teleoperated robot-assisted surgery INDUSTRIAL ROBOT-AN INTERNATIONAL JOURNAL Okamura, A. M. 2004; 31 (6): 499-508
  • Virtual remote center of motion control for needle placement robots. Computer aided surgery Boctor, E. M., Webster, R. J., Mathieu, H., Okamura, A. M., Fichtinger, G. 2004; 9 (5): 175-183

    Abstract

    We present an algorithm that enables percutaneous needle-placement procedures to be performed with unencoded, unregistered, minimally calibrated robots while removing the constraint of placing the needle tip on a mechanically enforced Remote Center of Motion (RCM).The algorithm requires only online tracking of the surgical tool and a five-degree-of-freedom (5-DOF) robot comprising three prismatic DOF and two rotational DOF. An incremental adaptive motion control cycle guides the needle to the insertion point and also orients it to align with the target-entry-point line. The robot executes RCM motion without having a physically constrained fulcrum point.The proof-of-concept prototype system achieved 0.78 mm translation accuracy and 1.4 degrees rotational accuracy (this is within the tracker accuracy) within 17 iterative steps (0.5-1 s).This research enables robotic assistant systems for image-guided percutaneous procedures to be prototyped/constructed more quickly and less expensively than has been previously possible. Since the clinical utility of such systems is clear and has been demonstrated in the literature, our work may help promote widespread clinical adoption of this technology by lowering system cost and complexity.

    View details for PubMedID 16192059

  • A modular 2-DOF force-sensing instrument for laparoscopic surgery MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2003, PT 1 Prasad, S. K., Kitagawa, M., Fischer, G. S., Zand, J., Talamini, M. A., Taylor, R. H., Okamura, A. M. 2003; 2878: 279-286
  • Recognition of operator motions for real-time assistance using virtual fixtures 11TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS - HAPTICS 2003, PROCEEDINGS Ming, L., Okamura, A. M. 2003: 125-131
  • The Haptic Scissors: Cutting in virtual environments 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS Okamura, A. M., Webster, R. J., Nolin, J. T., Johnson, K. W., Jafry, H. 2003: 828-833
  • Virtual fixture architectures for telemanipulation 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS Abbott, J. J., Okamura, A. M. 2003: 2798-2805
  • Uniting haptic exploration and display ROBOTICS RESEARCH Okamura, A. M. 2003; 6: 225-238
  • Robotic needle insertion: Effects of friction and needle geometry 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS O'Leary, M. D., Simone, C., Washio, T., Yoshinaka, K., Okamura, A. M. 2003: 1774-1780
  • Steady-hand teleoperation with virtual fixtures RO-MAN 2003: 12TH IEEE INTERNATIONAL WORKSHOP ON ROBOT AND HUMAN INTERACTIVE COMMUNICATION, PROCEEDINGS Abbott, J. J., Hager, G. D., Okamura, A. M. 2003: 145-151
  • Methods for intelligent localization and mapping during haptic exploration 2003 IEEE INTERNATIONAL CONFERENCE ON SYSTEMS, MAN AND CYBERNETICS, VOLS 1-5, CONFERENCE PROCEEDINGS Schaeffer, M. A., Okamura, A. M. 2003: 3438-3445
  • Virtual remote center of motion control for needle placement robots MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION - MICCAI 2003, PT 1 Boctor, E. M., Webster, R. J., Mathieu, H., Okamura, A. M., Fichtinger, G. 2003; 2878: 157-164
  • Activation cues and force scaling methods for virtual fixtures 11TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS - HAPTICS 2003, PROCEEDINGS Nolin, J. T., Stemniski, P. M., Okamura, A. M. 2003: 404-409
  • Analysis of virtual fixture contact stability for telemanipulation IROS 2003: PROCEEDINGS OF THE 2003 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Abbott, J. J., Okamura, A. M. 2003: 2699-2706
  • Spatial motion constraints: Theory and demonstrations for robot guidance using virtual fixtures 2003 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-3, PROCEEDINGS Marayong, P., Li, M., Okamura, A. M., Hager, G. D. 2003: 1954-1959
  • The effect of visual and haptic feedback on manual and teleoperated needle insertion MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION-MICCAI 2002, PT 1 Gerovichev, O., Marayong, P., Okamura, A. M. 2002; 2488: 147-154
  • On the display of haptic recordings for cutting biological tissues 10TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Chial, V. B., Greenish, S., Okamura, A. M. 2002: 80-87
  • Vision assisted control for manipulation using virtual fixtures: Experiments at macro and micro scales 2002 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS I-IV, PROCEEDINGS Bettini, A., Lang, S., Okamura, A., Hager, G. 2002: 3354-3361
  • Effect of virtual fixture compliance on human-machine cooperative manipulation 2002 IEEE/RSJ INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-3, PROCEEDINGS Marayong, P., Bettini, A., Okamura, A. 2002: 1089-1095
  • Measurement of the tip and friction force acting on a needle during penetration MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION-MICCAI 2002, PT 1 Kataoka, H., Washio, T., Chinzei, K., Mizuhara, K., Simone, C., Okamura, A. M. 2002; 2488: 216-223
  • Modeling of needle insertion forces for robot-assisted percutaneous therapy 2002 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS I-IV, PROCEEDINGS Simone, C., Okamura, A. M. 2002: 2085-2091
  • Building a task language for segmentation and recognition of user input to cooperative manipulation systems 10TH SYMPOSIUM ON HAPTIC INTERFACES FOR VIRTUAL ENVIRONMENT AND TELEOPERATOR SYSTEMS, PROCEEDINGS Hundtofte, C. S., Hager, G. D., Okamura, A. M. 2002: 225-230
  • Analysis of suture manipulation forces for teleoperation with force feedback MEDICAL IMAGE COMPUTING AND COMPUTER-ASSISTED INTERVENTION-MICCAI 2002, PT 1 Kitagawa, M., Okamura, A. M., Bethea, B. T., Gott, V. L., Baumgartner, W. A. 2002; 2488: 155-162
  • Feature-guided exploration with a robotic finger 2001 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS I-IV, PROCEEDINGS Okamura, A. M., Cutkosky, M. R. 2001: 589-596
  • Vision assisted control for manipulation using virtual fixtures IROS 2001: PROCEEDINGS OF THE 2001 IEEE/RJS INTERNATIONAL CONFERENCE ON INTELLIGENT ROBOTS AND SYSTEMS, VOLS 1-4 Bettini, A., Lang, S., Okamura, A., Hager, G. 2001: 1171-1176
  • Haptic surface exploration EXPERIMENTAL ROBOTICS VI Okamura, A. M., Costa, M. A., Turner, M. L. 2000; 250: 423-432
  • Haptic exploration of fine surface features ICRA '99: IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-4, PROCEEDINGS Okamura, A. M., Cutkosky, M. R. 1999: 2930-2936
  • Vibration feedback models for virtual environments 1998 IEEE INTERNATIONAL CONFERENCE ON ROBOTICS AND AUTOMATION, VOLS 1-4 Okamura, A. M., Dennerlein, J. T., Howe, R. D. 1998: 674-679
  • Haptic exploration of objects with rolling and sliding Okamura, A. M., Turner, M. L., Cutkosky, M. R. IEEE. 1997: 2485-2490