COHERENT HIGH-RESOLUTION ULTRASOUND REFLECTION MODE CT IMAGING.

A coherent ultrasound reflection-mode computerized tomography (CT) imaging method has been developed to image small (10 mm multiplied by 10 mm) areas in objects such as the liver. Since only a single radial scan and straight-line CT reconstruction are used, the processing time and computer as well as hardware requirements are reduced considerably compared to those of ordinary transmission or reflection CT. The main limitation of the method is the need for correction for speed variations in intervening media. This is done by tracing brightest sinusoids in the Radon space of the data to obtain estimates of the time shifts. Images of simulated objects, real phantoms, and liver specimens are presented and compared to images obtained by compound B-scans from the same objects. These images show that the resolution of the imaging method is about 0. 3 mm using a commercial 3. 5-MHz medium-focused transducer.