Improved Detection of Hepatic Metastases with Pulse-Inversion US during the Liver-specific Phase of SHU 508A: Multicenter Study

Abstract

PURPOSE: To compare conventional B-mode ultrasonography (US) alone with the combination of conventional B-mode US and contrast material-enhanced (SHU 508A) late-phase pulse-inversion US for the detection of hepatic metastases by using dual-phase spiral computed tomography (CT) as the standard of reference. MATERIALS AND METHODS: One hundred twenty-three patients underwent conventional US, US in the liver-specific phase of SHU 508A, and single-section spiral CT. US and CT images were assessed by blinded readers. Differences in sensitivity, specificity, and the number and smallest size of metastases at conventional and contrast-enhanced US were compared by using CT as the standard of reference. Lesion conspicuity was assessed objectively (quantitatively) and subjectively by one reader before and after contrast material administration. RESULTS: In 45 of 80 (56%) patients with metastases, more metastases were seen at contrast-enhanced US than at conventional US. In three of these patients, conventional US images appeared normal. The addition of contrast-enhanced US improved sensitivity for the detection of individual metastases from 71% to 87% (P <.001). On a patient basis, sensitivity improved from 94% to 98% (P =.44), and specificity improved from 60% to 88% (P <.01). Contrast enhancement improved the subjective conspicuity of metastases in 66 of 75 (88%) patients and the objective contrast by a mean of 10.8 dB (P <.001). Contrast-enhanced US showed more metastases than did CT in seven patients, and CT showed more than did contrast-enhanced US in one of 22 patients in whom an independent reference (magnetic resonance imaging, intraoperative US, or pathologic findings) was available. CONCLUSION: Contrast-enhanced US improved sensitivity and specificity in the detection of hepatic metastases.