Material Evaluation of PC-ISO for Customized, 3D Printed, Gynecologic Ir HDR Brachytherapy Applicators

Purpose: To evaluate the radiation attenuation properties of PC-ISO, a bio-compatible, sterilizable 3D printing material and its suitability for customized gynecologic (GYN) brachytherapy 15 applicators. Method: A custom radiochromic film dosimetry apparatus was 3D-printed in PC-ISO. The apparatus contained a single catheter channel and a slit to hold a radiochromic segment. A brachytherapy dose plan was computed to deliver a cylindrical dose distribution to the film. The dose plan used an 192Ir source and was normalized to 1500 cGy at 1 cm from the channel. The material 20 was evaluated by comparing the film exposure to an identical test done in water. The Hounsfield unit (HU) distribution was computed from a CT scan of the apparatus and compared to the HU distribution of water. The durability of PC-ISO was evaluated through multiple sterilization procedures. Results: The dose-depth curve of PC-ISO was within 1% of water between 1 cm and 6 cm from 25 the channel. The mean HU was -10 for PC-ISO and -1 for water. There was no visible damage to the apparatus after five sterilizations. Conclusions: PC-ISO is sufficiently water equivalent to be compatible with our HDR brachytherapy planning system and workflow, and therefore it is suitable for creating custom GYN brachytherapy applicators. We have since treated several patients with custom GYN applicators made of 30 PC-ISO when we felt it would improve their treatment.