Time reversal focusing through a human skull optimized by skull surface detection algorithm

Abstract

High-intensity focused ultrasounds are mainly envisioned to cure liver and prostate cancer. In order to cure brain tumors, it has been shown that time reversal coupled with amplitude compensation is an interesting technique to correct the aberrations induced by a human skull. This focusing technique should be improved by compensating the amplitude at the exact location of the skull. To measure the geometrical shape of the skull, two different techniques are investigated and compared in terms of precision and duration of the measurement. The first method is based on the measurement of the propagation time from the array to the skull and back of pulsed signals emitted and received by each pair of transducers of an echographic array of 128 transducers. For each pair, the reflection point on the skull is located on an ellipse whose centers correspond to the positions of the emitting and receiving elements. The envelope of the complete set of ellipses is then extracted, giving the shape of the skull. This technique is compared to echographic imaging of the skull using the same array. Comparisons between these techniques will be presented using the Phased Array Simulation software and the corresponding experimental focusing.