Hepatic tumor detection: MR Imaging and conventional US versus pulse-inversion harmonic US of NC100100 during its reticuloendothelial system-specific phase

PURPOSE: To compare conventional ultrasonography (US) and magnetic resonance (MR) imaging with contrast agent-enhanced US for detection of VX-2 liver tumors in rabbits. MATERIALS AND METHODS: Conventional gray-scale liver US was performed in 65 rabbits, 38 of which had VX-2 hepatic tumor implants. Twenty minutes after contrast agent injection, gray-scale pulse-inversion harmonic US images of the liver-specific phase were obtained. Following sacrifice of the animals, T1- and T2-weighted MR imaging was performed at 4-mm intervals. Pathologic analysis was performed as the reference standard. The capability of each imaging modality to correctly depict tumor presence or absence and the number of tumors was compared. RESULTS: Conventional US correctly depicted the presence or absence of tumors in 54 rabbits, for an accuracy of 83%, sensitivity of 71%, and specificity of 100%. With contrast-enhanced US, accuracy increased to 92% (60 correct cases); sensitivity, to 87%; and specificity, to 100%. MR imaging facilitated 56 correct diagnoses, for an accuracy of 86%, sensitivity of 82%, and specificity of 93%. There was a marginally significant difference between US with and US without contrast agent (P = .07) but not between MR imaging and contrast-enhanced US (P greater than or equal to .34). When the numbers of correctly detected tumors were compared, contrast-enhanced US performed significantly better than MR imaging (P = .02) and conventional US (P = .04). CONCLUSION: There was no significant difference between contrast-enhanced US and MR imaging in the detection of hepatic tumors, whereas contrast-enhanced US had the highest accuracy (92%) of the three modalities studied. (C) RSNA, 2002.