Feasibility Study of Polymer Gel Dosimetry Using a 3D Printed Phantom for Liver Cancer Radiotherapy

Abstract

In this study, a new three-dimensional (3D) volumetric dosimetry method utilizing gel dosimetry with a patient-specific (PS) 3D-printed phantom was developed. A PS 3D-printed phantom that closely mimics the actual tumor and surrounding tissues was demonstrated using a 3D printer (3Dison Plus, Lokit, Korea). MAGAT normoxic polymer gel was filled in the tumor-shaped cavity of the 3D-printed phantom to represent the real tumor. Seven identical gel samples for dosimetric calibration were irradiated at different doses and scanned using magnetic resonance imaging. A chlorinated polyethylene filament was utilized as the 3D printing material. The two-dimensional gamma passing rates using the film were 96.1% and 84.3% for the 3%/3 mm and the 2%/1 mm dose accuracy/distance-to agreement criteria, respectively. The radiation dose-R2 (relaxation rate) calibration, with a coefficient of determination (R2) of 0.997, was applied for the absolute dose calibration. The overall gross tumor volume shape and the dose distribution of the gel measurement agreed reasonably well with the plan results. The 3D gamma passing rate was 91.2% for the 3%/3 mm criteria and decreased to 82.3% for the 2%/1 mm criterion. Our results suggest that polymer gel dosimetry with the 3D-printed phantom allows direct validation of the 3D dose distribution.