Recurrent hepatocellular carcinoma versus radiation-induced hepatic injury: differential diagnosis with MR imaging

The objective of this study was to assess the value of MR imaging in the di fferentiation between a recurrent hepatocellular carcinoma (HCC) and a radi ation-induced hepatic injury. Nine male patients with suspected recurrence after radiotherapy for HCC underwent T-2 T-1-weighted imaging and Gd-DTPA e nhanced dynamic studies. T-2 relaxation times, signal intensity ratios in T -1-weighted images (WI) and the relative enhancement of the dynamic study w ere calculated. Recurrent tumors and the irradiated area showed similar ima ge characteristics: hypointense in T-1-WI and hyperintense in T-2-WI.T-2 va lues and signal intensity ratios in the T-1-WI were not significantly diffe rent. In the gadolinium-enhanced dynamic study, a recurrent HCC showed earl y enhancement, followed by a rapid washout. However, the irradiated liver p arenchyma showed hyperintensity from an early phase, and contrast enhanceme nt tended to be more prominent and prolonged at the end of the dynamic stud ies. The characteristic findings of the dynamic MR study enable us to disti nguish between a recurrent HCC and a radiation-induced hepatic injury. (C) 2001 Elsevier Science Inc. All rights reserved.