MR features of regenerative nodules and dysplastic nodules in the cirrhotic liver

In order to study MR features of the regenerative nodule (RN) and dysplastic nodule (DN) of the cirrhotic liver, 26 cases of cirrhotic liver with RNs and DNs, of which 8 cases accompanied with hepatocellular carcinoma, were subjected to MRI. Eighteen of 26 cases underwent additional enhanced MRI with administration of Gd-DTPA on T1WI and 10 of the 18 cases did additional SPIO (Feridex) enhancement on T2WI. Clinical data showed normal level of alpha-fetoprotein in 18 cases except 8 cases accompanied with HCC. The results showed that 12 cases had RNs with nodules measuring < 1 cm. The MR appearance of those RNs showed isointensity on T1WI and hypointensity on T2WI. The intensity of those RNs was isointense to the surrounding hepatic parenchyma on enhanced MRI with administration of Gd-DTPA or SPIO. Among the 14 cases of DNs, 8 cases had nodules measuring 1-3 cm in size and 6 had macroregenerative nodule measuring > 3 cm. In 8 cases with DNs measuring 1-3 cm in size, 5 cases appeared hyperintense on T1WI and hypointense on T2WI as well as the enhancement as that of nodules with < 1 cm in size; and the remaining 3 cases appeared hypointense on T1WI and hyperintense on T2WI, and were not isointense to the surrounding hepatic parenchyma on enhanced MRI but hyperintense on SPIO enhanced MRI. In 6 cases of macroregenerative nodule measuring > 3 cm in size, 2 cases appeared hyperintense to the surrounding hepatic parenchyma on T1, T2WI and enhanced MRI; 4 cases showed hyperintense on T1WI, and hypointense on T2WI and enhanced MRI. Sometimes, normal vessels were seen to pass through the surface of macroregenerative nodules. It was suggested that RNs of cirrhosis had features on MRI that usually allow distinction from hepatocellular carcinoma but not always from dysplastic nodules (DNs). A helpful distinction between HCC and DNs is that the latter are almost never hyperintense on T2WI. Additionally, low grade DNs appear hypointense on SPIO enhanced MRI.