Purpose: The use of contrast enhancers has widened the possibilities of sonographic imaging, and allows the differentiation of characteristic enhancement patterns leading to diagnosis in focal liver lesions. The aim of our study was to evaluate contrast ultrasound signs in diagnosing malignant liver lesions.
Methods: 86 patients with 100 solid liver lesions were enrolled. A baseline gray-scale sonogram was obtained with a multifrequency 4 C convex array probe, followed by contrast-enhanced sonography with a low mechanical index (<0.2) over 300 seconds. Final diagnosis was confirmed by histology or in case of haemangioma by CT/NMR and quantitative contrast harmonic imaging (CHI) with perfusion analysis (contrast).
Results: 55 malignant (6 HCC, 46 secondary malignant lesions - 3 of them lymphoma, 3 cholangiocarcinoma), and 45 benign lesions (8 FNH, 1 von Meyenburg complex, 1 granuloma, 3 adenoma, 21 hemangioma, 2 focal fat storage imbalances, 7 abscesses, one scar, and in one case normal liver) were found. 51/55 malignant (all but one filia and three HCC), but also 17/45 benign lesions showed hypoperfusion in the late phase. The ultrasound pattern in the arterial phase differed in malignant lesions: 22 lesions were initially hypervascular, 20 had rim enhancement and in 13 lesions there was a non-specific vascularisation. In all but one malignant lesion a diminishing of contrast agent in the late phase compared to the arterial phase with respect to the surrounding liver tissue was observed. Only three benign lesions with this later sign were falsely diagnosed as malignant: one adenoma, one epitheloid granuloma, and a scar. Quantitative perfusion pattern was analyzed exemplary. Diminishing of contrast agent in the late phase compared to the arterial phase with respect to the surrounding liver tissue as a sign for malignancy had a positive predictive value of 95%, a sensitivity of 98%, a negative predictive value of 98%, and a specificity of 93%.
Conclusions: Diminishing of contrast agent in the late phase compared to the arterial phase with respect to the surrounding liver tissue is a helpful sign in contrast enhanced ultrasound to diagnose malignancies.