Phase aberration correction and motion compensation for ultrasonic hyperthermia phased arrays: experimental results

In ultrasound hyperthermia, focal patterns generated by phased arrays can be degraded by phase errors due to tissue inhomogeneities, digitization of the driving signals, and imperfect fabrication of the transducers. The degree of degradation depends on the severity of phase aberrations. As predicted by simulation and verified by experimental results, focal degradation scales with the circular variance of phase errors. However, degraded power deposition patterns can be significantly improved after phase aberration correction, especially where patterns are complicated and the aberrations are severe. Also, as shown in motion compensation experiments, an aberration corrected pattern can be particularly sensitive to aberrator movement greater than the correlation length of the aberrator. After motion compensation, new sharply focused patterns can be accomplished, thus reducing the unwanted influence of "body" movement by stabilizing the positions of foci with respect to patient anatomy.<>