Comparison between conventional US and multi-frequency tissue harmonic US in imaging Hepatic focal lesion and gray-scale tissue mimicking phantom

The image of quality of 106 consecutive focal hepatic lesions (44 cysts, 40 solid lesions, and 22 intrahepatic duct stones or calcifications) and various targets (gray-scale targets, anechoic targets, and monofilament targets) in tissue mimicking phantom were examined with conventional US (CI) and 3 different modes of THI technique THI-1, THI-2, and THI-3 with transmitted frequencies of 2.5 MHz, 2.8 MHz, 3.0 MHz, respectively. Focal hepatic lesions and targets were divided into 2 or 3 groups according to the depth of lesion. Each set of images was evaluated by two radiologist. In clinical study (the margin and contrast of the lesions, internal echo and posterior sonic enhancement of cysts and posterior shadowing of calcification/stone). In phantom study (margin and contrast of targets). The contrast of all targets in phantom except monofilament target were measured using Image Pro-Plus (Media Cybemetics). Tissue harmonic US provides better image quality compared to conventional US. Variable transmitted frequency can be selected used in THI according to the depth of each hepatic lesion.