Kasra Naftchi-Ardebili

All Publications

• Focal Volume, Acoustic Radiation Force, and Strain in Two-Transducer Regimes IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL Naftchi-Ardebili, K., Menz, M. D., Salahshoor, H., Popelka, G. R., Baccus, S. A., Pauly, K. 2024; 71 (10): 1199-1216

  Abstract

  Transcranial ultrasound stimulation (TUS) holds promise for noninvasive neural modulation in treating neurological disorders. Most clinically relevant targets are deep within the brain (near or at its geometric center), surrounded by other sensitive regions that need to be spared clinical intervention. However, in TUS, increasing frequency with the goal of improving spatial resolution reduces the effective penetration depth. We show that by using a pair of 1-MHz orthogonally arranged transducers, we improve the spatial resolution afforded by each of the transducers individually, by nearly 40 folds, achieving a subcubic millimeter target volume of [Formula: see text]. We show that orthogonally placed transducers generate highly localized standing waves with acoustic radiation force (ARF) arranged into periodic regions of compression and tension near the target. We further present an extended capability of the orthogonal setup, which is to impart selective pressures-either positive or negative, but not both-on the target. Finally, we share our preliminary findings that strain can arise from both particle motion (PM) and ARF with the former reaching its maximum value at the focus and the latter remaining null at the focus and reaching its maximum around the focus. As the field is investigating the mechanism of interaction in TUS by way of elucidating the mapping between ultrasound parameters and neural response, orthogonal transducers expand our toolbox by making it possible to conduct these investigations at much finer spatial resolutions, with localized and directed (compression versus tension) ARF and the capability of applying selective pressures at the target.

  View details for DOI 10.1109/TUFFC.2024.3456048

  View details for Web of Science ID 001338565700012

  View details for PubMedID 39240744

• Biophysical effects and neuromodulatory dose of transcranial ultrasonic stimulation. ArXiv Nandi, T., Kop, B. R., Naftchi-Ardebili, K., Stagg, C. J., Pauly, K. B., Verhagen, L. 2024

  Abstract

  Transcranial ultrasonic stimulation (TUS) has the potential to usher in a new era for human neuroscience by allowing spatially precise and high-resolution non-invasive targeting of both deep and superficial brain regions. Currently, fundamental research on the mechanisms of interaction between ultrasound and neural tissues is progressing in parallel with application-focused research. However, a major hurdle in the wider use of TUS is the selection of optimal parameters to enable safe and effective neuromodulation in humans. In this paper, we will discuss the major factors that determine both the safety and efficacy of TUS. We will discuss the thermal and mechanical biophysical effects of ultrasound, which underlie its biological effects, in the context of their relationships with tunable parameters. Based on this knowledge of biophysical effects, and drawing on concepts from radiotherapy, we propose a framework for conceptualising TUS dose.

  View details for PubMedID 39010872

• Rank restriction for the variational calculation of two-electron reduced density matrices of many-electron atoms and molecules PHYSICAL REVIEW A Naftchi-Ardebili, K., Hau, N. W., Mazziotti, D. A. 2011; 84 (5)

  View details for DOI 10.1103/PhysRevA.84.052506

  View details for Web of Science ID 000296850500003