Phantoms and automated system for testing the resolution of ultrasound scanners

Tissue-mimicking phantoms and an automated system have been developed for testing the resolution performance of ultrasound scanners by determining detectability of low to higher contrast spherical lesions over the entire depth of field. Axial, lateral and elevational resolutions are accounted for simultaneously and equally. Tissue-mimicking spherical simulated lesions are either 3 or 4 mm in diameter and have one of four different intrinsic material contrasts. For each diameter and contrast, there is a set of 109 lesions in a regular array with coplanar centers extending from 0.5-15.5 cm in depth. With the scan slice superimposed on the spheres, the image is frame-grabbed for automated analysis. A diameter-dependent lesion signal-to- noise ratio is computed for each pixel position in the image, excluding a 5- mm boundary. Two universal thresholds, resulting from maximization of agreement between the automated system and human observers, give rise to a depth range, or 'resolution zone', over which detection exists for each type lesion.