The sector-vortex array: Acoustic field synthesis for tumor treatment

The sector-vortex array, which is a disk-shaped phase array with a geometric focus divided into N sectors, can directly synthesize an acoustic field suitable for treating small tumors. By driving the N sectors with such a phase distribution that the phase rotates m (≤N/4) times per rotation around the disk, an annular acoustic field pattern approximated by an m-th order Bessel function is produced on the geometric focal plane. The diameter of the annulus can be adjusted by controlling the mode number m. Moreover, ellipsoidal field patterns fitting the tumor shape can be produced by modulating the phase rotation. The sector-vortex array partitioned into two tracks can produce even more useful patterns when it is driven with a phase difference (--π) between the tracks. Combining these two field patterns by time-sharing, one can obtain a useful heat irradiation pattern for tumor treatment without leaving the marginal region of the tumor unheated