Author: Kenneth L. Homann, Natalie A Lockney, Hong Zhang 👨🔬
Affiliation: Department of Radiation Oncology, Vanderbilt University Medical Center, Vanderbilt University Medical Center 🌍
Purpose: The aim of this study is to develop a treatment planning methodology utilizing liver functional imaging via contrast-enhanced Magnetic Resonance Imaging (MRI) in patients undergoing stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC). This novel approach can preserve liver dose while ensuring tumor coverage and may diminish risk of radiation-induced liver disease (RILD).
Methods: Patients will be eligible who meet the following criteria: clinical diagnosis of hepatocellular carcinoma (pathologic diagnosis not required), age >18 years, planned to undergo SBRT, and able to understand and provide informed consent. The CT-simulation scan and MRI with contrast for a patient will be registered. Upon registration, MRI will be superimposed with CT as the voxel function in Figure 1. The cost function of Treatment Planning System (TPS) aims to maintain the dose within a specified range while optimizing the dose to the target (such as a tumor or treatment volume). C=wtCtarget+∑jwojCOARj+Cadditionalconstrains where wt and woj are the weights for the tumor and each organ at risk, respectively. Ctarget is the target penalty term. COARj represents each organ’s penalty term. Cadditional constraints includes any other specific constraints, like homogeneity or gradient requirements. Ctarget=∑i∈Target(Di-Dprescription)2 where Di is the dose to voxel i within the target, and Dprescription is the prescribed dose. COARj=∑i∈OARmax(0,Di-DOAR_threshold)2 where Di is the dose to voxel i in the OAR, max() is the maximum function and DOAR_threshold is the dose threshold for that organ. After including the function Fi of voxel i, the cost for the OAR (liver in our case) is revised as: COARj=∑i∈OARFimax(0,Di-DOAR_threshold)2
Results: The V15Gy of liver FDVH improved from 25.22% to 22.05%, while the PTV DVH exhibited no significant change in Figure 2,3 for one example case. Additional patients will be enrolled.
Conclusion: This novel approach may diminish potential liver function impairment while maintaining effective tumor coverage.