Superparamagnetic iron oxide-enhanced MR imaging for early and late radiation-induced hepatic injuries

Superparamagnetic iron oxide (SPIO)-enhanced MRI was performed in twenty-one patients undergoing proton-beam radiotherapy for hepatocellular carcinomas. Patients were divided into two groups: early and late phase hepatic injuries. Each group was investigated 3 to 9 weeks and 4 to 65 months after the start of irradiation, respectively. T1-weighted, T2-weighted, and T2∗-weighted images were obtained before and after SPIO administration. In all postcontrast sequences in the early phase, irradiated livers demonstrated relatively higher intensity than nonirradiated livers and the radiation-to-liver contrast-to-noise ratio (C/N) was improved. Postcontrast T2∗-weighted images showed the highest C/N. In the late phase, the irradiated areas showed high intensity on T2-weighted images and low intensity on T1-weighted images without SPIO, while high intensity on T1-weighted images with SPIO. The C/N increased with SPIO in all sequences and postcontrast T2-weighted images showed the highest C/N in the late phase. SPIO-enhanced MRI is useful to evaluate this entity both in the early and late phase of clinical studies.