Small hepatocellular carcinomas: improved sensitivity by combining gadoxetic acid-enhanced and diffusion-weighted MR imaging patterns.

Purpose: To determine if the combination of gadoxetic acid-enhanced magnetic resonance (MR) imaging and diffusion-weighted (DW) imaging helps to increase accuracy and sensitivity in the diagnosis of small hepatocellular carcinomas (HCCs) compared with those achieved by using each MR imaging technique alone.
Materials and Methods: The institutional review board approved this retrospective study and waived the requirement for informed consent. The study included 130 patients (95 men, 35 women) with 179 surgically confirmed small HCCs (≤2.0 cm) and 130 patients with cirrhosis (90 men, 40 women) without HCC who underwent gadoxetic acid-enhanced MR imaging and DW imaging at 3.0 T between May 2009 and July 2010. Three sets of images were analyzed independently by three observers to detect HCC: a gadoxetic acid set (unenhanced, early dynamic, and hepatobiliary phases), a DW imaging set, and a combined set. Data were analyzed by using alternative-free response receiver operating characteristic analysis. Diagnostic accuracy (area under the receiver operating characteristic curve [A(z)]), sensitivity, specificity, and positive predictive value were calculated.
Results: The mean A(z) values for the combined set (0.952) were significantly higher than those for the gadoxetic acid set (A(z) = 0.902) or the DW imaging set alone (A(z) = 0.871) (P ≤ .008). On a per-lesion basis, observers showed higher sensitivity in their analyses of the combined set (range, 91.1%-93.3% [163-167 of 179]) than in those of the gadoxetic acid set (range, 80.5%-82.1% [144-147 of 179]) or the DW imaging set alone (range, 77.7%-79.9% [139-143 of 179]) (P ≤ .003). Positive predictive values and specificity for all observers were equivalent for the three imaging sets.
Conclusion: The combination of gadoxetic acid-enhanced MR imaging and DW imaging yielded better diagnostic accuracy and sensitivity in the detection of small HCCs than each MR imaging technique alone.
(© RSNA, 2012)