Model 534 tissue-mimicking (TM) phantom are designed to evaluate the performance of diagnostic ultrasound imaging systems. These phantoms contain 81 anechoic, cylindrical target structures of varying sizes. The targets are positioned in-line vertically, to permit an entire target group to be displayed in one view. Due to the acoustic similarity of the background material and the anechoic targets, artifacts caused by distortion, shadowing or enhancement have been eliminated.