A new algorithm for dynamic focusing of phased-array hyperthermia applicators through tissue inhomogeneities

A prototype needle hydrophone array for acoustic feedback during phased-array hyperthermia treatments was presented previously. The authors present a new algorithm for adaptive dynamic focusing of phased-array applicators in the presence of inhomogeneities. This algorithm uses measurements from a limited number of acoustic sensors such as those on the needle hydrophone array. The algorithm is based on a Taylor series expansion of the (measured) propagation operator from the array elements, in the vicinity of the implanted acoustic sensors. The authors show that the new algorithm does not require prior knowledge of the applicator geometry and that all parameters for correction terms can be measured directly at the sensor location. Experimental results of dynamic focusing based on the new algorithm are presented using a 1D cylindrical section phased-array prototype