Added value of subtraction imaging in detecting arterial enhancement in small (<3 cm) hepatic nodules on dynamic contrast-enhanced MRI in patients at high risk of hepatocellular carcinoma

Abstract

OBJECTIVES: To determine the importance of arterial enhancement in diagnosing small (<3 cm) hepatocellular carcinomas (HCCs) and to evaluate the added value of dynamic subtraction magnetic resonance imaging (MRI) in detecting arterial enhancement in small (<3 cm) hepatic nodules in high-risk patients. METHODS: Eighty-six patients with 135 pathologically confirmed small (<3 cm) hepatic nodules (104 HCCs, 31 benign nodules) underwent MRI before curative surgery. Arterial enhancement was determined by three methods: (1) visual assessment of the arterial phase alone, (2) visual comparison of the arterial phase with the unenhanced phase and (3) additional review of subtraction images. The diagnostic performance of each method was calculated and compared using generalised estimating equations analysis. RESULTS: Arterial enhancement demonstrated high positive predictive value (PPV) (96.5-98.9 %) and specificity (90.3-96.8 %), but low negative predictive value (NPV) (54.6-62.5 %) and intermediate sensitivity (76-79.8 %) for diagnosing small HCCs. Diagnostic performance was highest for subtraction imaging. There were significant differences among the three methods in sensitivity (P = 0.04), accuracy (P = 0.044), PPV (P < 0.001) and NPV (P = 0.024), but not in specificity (P = 0.167). CONCLUSION: The accurate detection of arterial enhancement in small hepatic nodules is important for diagnosing HCC and may be enhanced by subtraction imaging.