The sequential change of MRI signal intensity in normal liver after radiotherapy for hepatocellular carcinoma

To differentiate the interval change of irradiated normal liver from other pathologic status, our study observed early and late MRI signal changes based on radiation dose distribution in normal liver after three-dimensional conformal radiotherapy. We retrospectively evaluated 21 patients with hepatocellular carcinoma who received 40 Gy/16 fractions or 54 Gy/27 fractions radiotherapy of curative aim. The early and late terms were defined as 2 to 4 months and 10 to 14 months after radiotherapy, respectively. The simulation CT, follow-up MRI, and information regarding dose distribution were fused using the deformable registration technique. We evaluated various MRI image sets after gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid enhancement. The five regions of interest were drawn according to radiation dose distribution (Vx: The volume corresponding to the range of total irradiation dose; V_>90%, V_60-90%, V_30-60%, V_5-30%, and V_<5%), and an ANOVA test was performed to compare signal differences between regions. We analyzed 19 and 11 cases of early and late term MRIs, respectively. In the early and late term, the V>90% of hepatobiliary phase images (p < 0.001 and p = 0.005, respectively) and T2-weighted images (p = 0.048 and p <0.001, respectively) were stratified with other regions showing the low and high signal, respectively. High radiation dose with curative intent can affect MRI signals on hepatobiliary phase and T2-weighted images.