Objective: The aim of this study was to investigate the usefulness of unenhanced and enhanced MR imaging in evaluating the response of hepatocellular carcinoma to percutaneous injection of ethanol.
Subjects and methods: Thirty-one patients with 40 hepatocellular carcinomas less than 5 cm in diameter were examined with MR imaging before and after percutaneous injection of ethanol. Unenhanced T1- and T2-weighted and contrast-enhanced T1-weighted spin-echo images were obtained. CT and percutaneous biopsy were performed 1 month after the final injection of ethanol and repeated at 6-month intervals to establish the outcome of treatment: complete tumor necrosis was shown in 36 lesions and incomplete tumor necrosis was seen in four lesions.
Results: Of the 36 proved necrotic lesions, 31 showed homogeneously low signal intensity on T2-weighted MR images obtained after treatment, owing to coagulative necrosis of the tumor. In the remaining five necrotic lesions, hypointense and hyperintense areas coexisted; the hyperintense areas were caused by liquefactive necrotic material in two cases and by chronic inflammatory tissue along the boundary of the necrotic area in three cases. None of the 36 necrotic lesions showed contrast enhancement on T1-weighted images obtained after IV injection of gadopentetate dimeglumine. In the four lesions with incomplete necrosis, the viable portion of the tumor was identified as a hyperintense area on T2-weighted images and as an enhancing area on contrast-enhanced T1-weighted images. No correlation was found between lesion features on unenhanced T1-weighted images and outcome of therapy.
Conclusion: Contrast-enhanced T1-weighted MR images allow a reliable evaluation of the effectiveness of treatment and are more accurate than unenhanced MR studies. Contrast-enhanced MR imaging may be considered a valuable alternative to contrast-enhanced CT in the follow-up of hepatocellular carcinomas treated with percutaneous injection of ethanol.