A disk-shaped phased array with a geometric focus di vided into N sectors (“sector-vortex” array) can directly synthesize an acoustic field suitable for heating nonsuperficial small tumors. By driving the N sectors with a phase that rotates M(≤ N/2) times per revolution around the disk, an annular vortex shaped acoustic field pattern is produced that is approximated by an Mth-order Bessel function on the geometric focal plane. The diameter of the annulus can be adjusted to the tumor size by controlling the mode number M. Moreover, unwanted acoustic “hot spots” are not formed between the array and the focal plane or beyond the focal plane. The sector-vortex array partitioned into multiple tracks can synthesize more complicated and useful patterns by controlling the acoustic interference between the fields produced by each track. Multitrack arrays also allow a larger diameter foci to be formed, and the heating field can be split into more than one annulus along the depth axis. Acoustic field patterns that can be synthesized by the sector-vortex array are studied using appropriate numerical simulations. The steady state temperature distribution around a tumor model, produced by time-sharing irradiation (scanning) between two different field patterns, is computed by solving a bioheat equation numerically.
|Number of pages||9|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|Publication status||Published - 1989 Mar|
ASJC Scopus subject areas
- Acoustics and Ultrasonics
- Electrical and Electronic Engineering