SU-E-J-198: Preliminary Study On Liver Radiation Response to Stereotactic Body Radiotherapy in Patients with Hepatocellular Carcinoma Based On MRI

Abstract

Purpose: To develop a method to study the MRI response of tumor and hepatic parenchyma to stereotactic body radiotherapy (SBRT) in patients with hepatocellular carcinoma (HCC). Methods: Two adult patients with HCC who received SBRT were recruited in this IRB-approved study. T1-weighted delayed phase contrast Eovist enhanced MRI were performed immediately prior to and three months after SBRT. The time between contrast injection and MRI acquisition was identical for both pre-and post-SBRT imaging sessions. The patients received 3D conformal SBRT with a total dose of 40 Gy in 5 fractions. Both MRI images were rigidly registered to the planning computed tomography (CT) data set and the 3-dimensional (3D) dosimetry data, focusing on local alignment in the tumor region. The average MRI intensity in the spleen was calculated for the pre-and post-SBRT images, and subtracted to reduce the effects of different imaging conditions. For each 4.9mm by 4.9mm by 6mm voxel in a region of interest (ROI) delimited by the liver contour and the 20 Gy isodose line, the difference in MRI intensity between pre-and post-SBRT images was generated and correlated to radiation dose deposited in that voxel. Results: The Pearson correlation coefficient between MRI intensity change and dose was 0.58 (p<0.0001) for patient A and 0.33 (p<0.0001) for the patient B. Conclusion: We have developed a method to study tumor and hepatic parenchyma response to radiation dose in HCC patients treated with SBRT. Our preliminary data suggest a correlation between the radiologic response and dose in HCC p333atients treated with SBRT, and warrant further study with more patients.