Split spectrum processing for enhanced detection of the ultrasonic echo of a moving target in biological tissues

This paper describes a biological application for split spectrum processing (SSP). The ultrasonic control of cryosurgery has been reported previously. It was demonstrated chat the echo of the advancing freezing front could be detected during a freeze-thaw cycle. However, the speckle noise can mask the target signal, leading to difficulties in its detection. In this study, a SSP algorithm with a minimisation technique was implemented and compared to linear bandpass filtering. The optimum set of processing parameters for SSP (half-power bandwidth and number of filters, location of the bank of bandpass filters) and for linear filtering (half-power bandwidth and centre frequency) were determined experimentally. Both filtering techniques were successful in locating the target. However, optimum SNR enhancement and axial resolution were achieved with the non-linear minimisation algorithm, which permits rapid and automatic detection of the moving freezing front during cryosurgery