Abstract
Purpose
Focused ultrasound (FUS) is emerging as an effective modality for clinical therapy. The phased array allows fast focus shifting electronically, but such focus shifting distance is quite limited due to the presence of a grating lobe and reduced acoustic pressure at the shifted focus. In addition, a small focus is preferred to enhance the treatment safety and efficacy, especially in neurological applications. However, because of the diffraction limit the size of most of the focal region from a concave transducer cannot be less than a wavelength.
Methods
In order to enhance the focusing ability (i.e., the acoustic pressure at the focus and the − 6 dB focused beam area) over a large focus shifting distance and reducing the focal size, a cylindrical concave phased array transducer with a large focusing angle was proposed and evaluated numerically. The generated acoustic field was simulated using the k-space pseudospectral method by varying the driving frequency, focusing angle, and focus shifting distance.
Results
It is found that the fully enclosed cylindrical design (focusing angle of 360°) could achieve high acoustic pressure and small sub-wavelength focused beam (i.e., < 2 mm2) simultaneously at the focus shifting up to 40 mm in comparison to those with a small focusing angle (i.e., 90°).
Conclusion
Such a fully enclosed cylindrical design may result in the FUS application throughout a large region-of-interest with satisfactory and almost consistent focusing abilities. Therefore, the therapeutic safety and efficacy may be improved.
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Zhou, Y. Simulation of the Sub-Wavelength Focusing Capability of Cylindrical Concave Phased Array. J. Med. Biol. Eng. 42, 747–756 (2022). https://doi.org/10.1007/s40846-022-00745-0
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DOI: https://doi.org/10.1007/s40846-022-00745-0