Development of a Robust, Accurate Ultrasonic Tracking System for Image Guided Surgery

As development of the 75 kHz 3D ultrasonic position system for Image Guided Surgery continues, major advances have been made in the hardware, and system testing. The hardware contains eight analog receiver circuits each with a 75 kHz band pass filter allowing the receiver signals to be captured with minimum noise distortion improving system reliability and accuracy. 1D testing showed sub millimeter accuracy except in transition regions where the time delay jumps to the next wavelength. Currently the 3D system software uses the ATOF formulation using speed of sound as a known and can handle the eight TOF inputs per transmitter. The system algorithm developed can adjust the receiver and TOF matrices if four or less receivers become occluded (TOF = 0) enhancing system robustness. Presently, the average RMS error reported for the 3D system ranges between 2.0 - 2.5 cm and depends heavily on the critical time delay model developed. Furthermore, the receiver circuitry has been packaged into an enclosure and a portable test bench has been designed and manufactured