ENHANCED IMAGE RESOLUTION OF DUAL-MODE ULTRASOUND ARRAY USING CODED EXCITATION

We have previously shown that a prototype 64-element 1 MHz concave DMUA has lateral and axial resolution 1.1 mm and 2.6 mm. While the lateral resolution is acceptable and compares favorably with abdominal diagnostic probes, the axial resolution is very poor. It must be improved by a factor of 2 or more to provide more uniform resolution. We have investigated the use of coded excitation and pseudoinverse filtering for enhancing the axial resolution of DMUA. Image data were collected from a 3D quality assurance phantom with an egg-shaped contrast target. The contrast ratio was 3.35, 7.8, and 6.6 and the axial resolution was 2.6, 2.5, and 1.65 mm for conventional pulse-echo, matched filter compression and inverse filter compression, respectively. Thus one can see that approximately 33% improvement in resolution was achievable without significant loss in contrast ratio.