Dr. Herickhoff has broad experience in ultrasound research & development, spanning 14 years in both academia and industry (GE Global Research and Philips Medical Systems). He currently serves as Deputy Director of the Radiological Sciences Laboratory, and his current research interests include novel medical ultrasound transducer designs and methods for elasticity, contrast, and flow imaging, and specialized ultrasound imaging systems for pediatrics and interventional procedure guidance.
Education & Certifications
Ph.D., Duke University, Biomedical Engineering (2011)
M.S., Duke University, Biomedical Engineering (2009)
B.S., University of Notre Dame, Electrical Engineering (2005)
Ultrasound/microbubble-mediated targeted delivery of anticancer microRNA-loaded nanoparticles to deep tissues in pigs.
Journal of controlled release : official journal of the Controlled Release Society
In this study, we designed and validated a platform for ultrasound and microbubble-mediated delivery of FDA-approved pegylated poly lactic-co-glycolic acid (PLGA) nanoparticles loaded with anticancer microRNAs (miRNAs) to deep tissues in a pig model. Small RNAs have been shown to reprogram tumor cells and sensitize them to clinically used chemotherapy. To overcome their short intravascular circulation half-life and achieve controlled and sustained release into tumor cells, anticancer miRNAs need to be encapsulated into nanocarriers. Focused ultrasound combined with gas-filled microbubbles provides a noninvasive way to improve the permeability of tumor vasculature and increase the delivery efficiency of drug-loaded particles. A single handheld, curvilinear ultrasound array was used in this study for image-guided therapy with clinical-grade SonoVue contrast agent. First, we validated the platform on phantoms to optimize the microbubble cavitation dose based on acoustic parameters, including peak negative pressure, pulse length, and pulse repetition frequency. We then tested the system in vivo by delivering PLGA nanoparticles co-loaded with antisense-miRNA-21 and antisense-miRNA-10b to pig liver and kidney. Enhanced miRNA delivery was observed (1.9- to 3.7-fold increase) as a result of the ultrasound treatment compared to untreated control regions. Additionally, we used highly fluorescent semiconducting polymer nanoparticles to visually assess nanoparticle extravasation. Fluorescent microscopy suggested the presence of nanoparticles in the extravascular compartment. Hematoxylin and eosin staining of treated tissues did not reveal tissue damage. The results presented in this manuscript suggest that the proposed platform may be used to safely and noninvasively enhance the delivery of miRNA-loaded nanoparticles to target regions in deep organs in large animal models.
View details for DOI 10.1016/j.jconrel.2019.07.024
View details for PubMedID 31326463
Unsupervised clustering method to convert high-resolution magnetic resonance volumes to three-dimensional acoustic models for full-wave ultrasound simulations.
Journal of medical imaging (Bellingham, Wash.)
2019; 6 (3): 037001
Simulations of acoustic wave propagation, including both the forward and the backward propagations of the wave (also known as full-wave simulations), are increasingly utilized in ultrasound imaging due to their ability to more accurately model important acoustic phenomena. Realistic anatomic models, particularly those of the abdominal wall, are needed to take full advantage of the capabilities of these simulation tools. We describe a method for converting fat-water-separated magnetic resonance imaging (MRI) volumes to anatomical models for ultrasound simulations. These acoustic models are used to map acoustic imaging parameters, such as speed of sound and density, to grid points in an ultrasound simulation. The tissues of these models are segmented from the MRI volumes into five primary classes of tissue in the human abdominal wall (skin, fat, muscle, connective tissue, and nontissue). This segmentation is achieved using an unsupervised machine learning algorithm, fuzzy c-means clustering (FCM), on a multiscale feature representation of the MRI volumes. We describe an automated method for utilizing FCM weights to produce a model that achieves ∼ 90 % agreement with manual segmentation. Two-dimensional (2-D) and three-dimensional (3-D) full-wave nonlinear ultrasound simulations are conducted, demonstrating the utility of realistic 3-D abdominal wall models over previously available 2-D abdominal wall models.
View details for DOI 10.1117/1.JMI.6.3.037001
View details for PubMedID 31338389
View details for PubMedCentralID PMC6643101
- Axially-segmented cylindrical array for intravascular shear wave imaging SPIE-INT SOC OPTICAL ENGINEERING. 2019
Versatile Low-Cost Volumetric 3-D Ultrasound Platform for Existing Clinical 2-D Systems
IEEE TRANSACTIONS ON MEDICAL IMAGING
2018; 37 (10): 2248–56
Ultrasound imaging has indications across many areas of medicine, but the need for training and the variability in skill and acquired image quality among 2-D ultrasound users have limited its wider adoption and utilization. Low-cost volumetric ultrasound with a known frame of reference has the potential to lower these operator-dependent barriers and enhance the clinical utility of ultrasound imaging. In this paper, we improve upon our previous research-scanner-based prototype to implement a versatile volumetric imaging platform for existing clinical 2-D ultrasound systems. We present improved data acquisition and image reconstruction schemes to increase quality, streamline workflow, and provide real-time visual feedback. We present initial results using the platform on a Vimedix simulator, as well as on phantom and in vivo targets using a variety of clinical ultrasound systems and probes.
View details for DOI 10.1109/TMI.2018.2821901
View details for Web of Science ID 000446342100008
View details for PubMedID 29993653
- Low-cost Volumetric Ultrasound by Augmentation of 2D Systems: Design and Prototype ULTRASONIC IMAGING 2018; 40 (1): 35–48
Intravascular acoustic radiation force imaging: Feasibility study
IEEE International Ultrasonics Symposium (IUS)
View details for DOI 10.1109/ULTSYM.2015.0118
Intracranial Dual-Mode IVUS and Hyperthermia Using Circular Arrays: Preliminary Experiments
2013; 35 (1): 17–29
In this study, we investigated the feasibility of using 3.5-Fr (3 Fr = 1 mm) circular phased-array intravascular ultrasound (IVUS) catheters for minimally invasive, image-guided hyperthermia treatment of tumors in the brain. Feasibility was demonstrated in two ways: (1) by inserting a 3.5-Fr IVUS catheter through skull burr holes, for 20 MHz brain imaging in the pig model, and (2) by testing a modified circular array for therapy potential with 18.5-MHz and 9-MHz continuous wave (CW) excitation. The imaging transducer's performance was superior to our previous 9-MHz mechanical IVUS prototype. The therapy catheter transducer was driven by CW electrical power at 18.5 MHz, achieving temperature changes reaching +8°C at a depth of 2 mm in a human glioblastoma grown on the flank of a mouse with minimal transducer resistive heating of +2°C. Further hyperthermia trials showed that 9-MHz CW excitation produced temperature changes of +4.5°C at a depth of 12 mm-a sufficient temperature rise for our long-term goal of targeted, controlled drug release via thermosensitive liposomes for therapeutic treatment of 1-cm-diameter glioblastomas.
View details for DOI 10.1177/0161734612469372
View details for Web of Science ID 000329394300002
View details for PubMedID 23287504
View details for PubMedCentralID PMC3823244
DUAL-MODE IVUS TRANSDUCER FOR IMAGE-GUIDED BRAIN THERAPY: PRELIMINARY EXPERIMENTS
ULTRASOUND IN MEDICINE AND BIOLOGY
2011; 37 (10): 1667–76
In this study, we investigated the feasibility of using 3.5-Fr intravascular ultrasound (IVUS) catheters for minimally-invasive, image-guided hyperthermia treatment of tumors in the brain. Feasibility was demonstrated by: (1) retro-fitting a commercial 3.5-Fr IVUS catheter with a 5 × 0.5 × 0.22 mm PZT-4 transducer for 9-MHz imaging and (2) testing an identical transducer for therapy potential with 3.3-MHz continuous-wave excitation. The imaging transducer was compared with a 9-Fr, 9-MHz ICE catheter when visualizing the post-mortem ovine brain and was also used to attempt vascular access to an in vivo porcine brain. A net average electrical power input of 700 mW was applied to the therapy transducer, producing a temperature rise of +13.5°C at a depth of 1.5 mm in live brain tumor tissue in the mouse model. These results suggest that it may be feasible to combine the imaging and therapeutic capabilities into a single device as a clinically-viable instrument.
View details for DOI 10.1016/j.ultrasmedbio.2011.06.017
View details for Web of Science ID 000295541600015
View details for PubMedID 21856073
View details for PubMedCentralID PMC3177008
Dual-Mode IVUS Catheter for Intracranial Image-Guided Hyperthermia: Feasibility Study
IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL
2010; 57 (11): 2572–84
In this study, we investigated the feasibility of modifying 3-Fr IVUS catheters in several designs to potentially achieve minimally-invasive, endovascular access for image-guided ultrasound hyperthermia treatment of tumors in the brain. Using a plane wave approximation, target frequencies of 8.7 and 3.5 MHz were considered optimal for heating at depths (tumor sizes) of 1 and 2.5 cm, respectively. First, a 3.5-Fr IVUS catheter with a 0.7-mm diameter transducer (30 MHz nominal frequency) was driven at 8.6 MHz. Second, for a low-frequency design, a 220-μm-thick, 0.35 x 0.35-mm PZT-4 transducer--driven at width-mode resonance of 3.85 MHz--replaced a 40-MHz element in a 3.5-Fr coronary imaging catheter. Third, a 5 x 0.5-mm PZT-4 transducer was evaluated as the largest aperture geometry possible for a flexible 3-Fr IVUS catheter. Beam plots and on-axis heating profiles were simulated for each aperture, and test transducers were fabricated. The electrical impedance, impulse response, frequency response, maximum intensity, and mechanical index were measured to assess performance. For the 5 x 0.5-mm transducer, this testing also included mechanically scanning and reconstructing an image of a 2.5-cm-diameter cyst phantom as a preliminary measure of imaging potential.
View details for DOI 10.1109/TUFFC.2010.1723
View details for Web of Science ID 000283944900020
View details for PubMedID 21041144
View details for PubMedCentralID PMC3018697
Dual-Mode Intracranial Catheter Integrating 3D Ultrasound Imaging and Hyperthermia for Neuro-oncology: Feasibility Study
2009; 31 (2): 81–100
In this study, we investigated the feasibility of an intracranial catheter transducer with dual-mode capability of real-time 3D (RT3D) imaging and ultrasound hyperthermia, for application in the visualization and treatment of tumors in the brain. Feasibility is demonstrated in two ways: first by using a 50-element linear array transducer (17 mm x 3.1 mm aperture) operating at 4.4 MHz with our Volumetrics diagnostic scanner and custom, electrical impedance-matching circuits to achieve a temperature rise over 4 degrees C in excised pork muscle, and second, by designing and constructing a 12 Fr, integrated matrix and linear-array catheter transducer prototype for combined RT3D imaging and heating capability. This dual-mode catheter incorporated 153 matrix array elements and 11 linear array elements diced on a 0.2 mm pitch, with a total aperture size of 8.4 mm x 2.3 mm. This 3.64 MHz array achieved a 3.5 degrees C in vitro temperature rise at a 2 cm focal distance in tissue-mimicking material. The dual-mode catheter prototype was compared with a Siemens 10 Fr AcuNav catheter as a gold standard in experiments assessing image quality and therapeutic potential and both probes were used in an in vivo canine brain model to image anatomical structures and color Doppler blood flow and to attempt in vivo heating.
View details for DOI 10.1177/016173460903100201
View details for Web of Science ID 000267182100001
View details for PubMedID 19630251
View details for PubMedCentralID PMC2810199
- Intracranial catheter for integrated 3D ultrasound Imaging & hyperthermia: Feasibility study IEEE. 2007: 208–11