Real-time dynamic focusing through tissue inhomogeneities during hyperthermia treatments with phased arrays

A needle probe hydrophone array made of discrete PVDF elements has been designed and fabricated at our laboratory. Such a probe can obtain complex acoustic pressure measurements at or near the tumor site. To extend the region over which these measurements may be used to focus a phased array, a real-time measurement system is needed, along with a method of extrapolating the data to points other than those measured by the probe. We describe such a real-time dynamic focusing algorithm that uses measurements from the full-set of hydrophone array elements in estimating the bearing and range of the elements of the transmitting array. In this way, a measurement of the radius of curvature of the wave front due to an array element is made along the span of the array, which extends the region of reliable refocusing. An outline of the steps of the refocusing algorithm along with simulation and experimental results are given. Finally, we describe the architecture of a real-time system for refocusing currently being designed for this purpose