A microprocessor-based spatial-locating system for use with diagnostic ultrasound

Ultrasound is being used in a growing number of clinical settings and offers the potential for supplementing or replacing many X-ray procedures at significantly reduced cost and risk to the patient. Medical applications of ultrasound have been largely qualitative due to an inability to locate the acoustic beam with respect to a coordinate system. A new method for determining the location and orientation of these beams has been developed which incorporates a dedicated micro-processor. The technique involves measuring the transit times of sparkgenerated shock waves. An Intel 8080 processor controls the operation of the system and performs all the computations required to determine the location and orientation of the ultrasound beam with respect to a known coordinate system. Approximately 2800 bytes of read-only memory and 250 bytes of random-access memory are required. System control, the reading of transit times from external counters, and the display of computed results are accomplished with a total of 2 input and 2 output ports. A 32-bit floating-point mathematics program including square root is necessary in order to obtain spatial resolution of ± 0.6 mm within a cubic volume 50cm on a side. The microprocessor performs error checking on the data and will automatically initiate a new measurement sequence should error limits be exceeded.