Room: Exhibit Hall | Forum 3
Purpose: Bolus for electron beam therapy for skin cancer is commonplace in most clinics. In some circumstances an external shield made of lead with an opening for the beam can be placed on the surface of the patient creating a sharper penumbra. We have developed a novel approach using custom designed 3-D printed bolus that will improve conformation to the patient anatomy and is customizable in thickness delivering a more uniform and reproducible dose. Built in to these custom compensating boluses are 3-D printed shielding for skin collimation using 3-D printed materials which could perfectly match the field opening created by the treatment planning system.
Methods: The 3-D printed boluses were designed using Phillips Pinnacle TPS and printed on a Lulzbot TAZ6 3-D printer using NinjaFlex material at a 90% fill. The shields were designed in Pinnacle but were altered with 3D Slicer and printed with a high-density, copper-infused PLA that cerrobend could be added to increase shielding. In order to validate the custom boluses prior to clinical use, a CT scan of the bolus was performed and Pinnacleâ€™s density profile tools were used to measure the variation in density for each bolus. To compare surface dose to the TPS, OSLD measurements were performed at points under both the bolus and the shield.
Results: The mean density of the material was 0.99 Â± 0.03 g/cmÂ³ with a maximum deviation of 10% at the walls of the bolus. The OSLD dose measurements agreed with the treatment planning system dose calculations within 3% under the bolus and within 1 cGy under the shields.
Conclusion: Our custom 3-D printed compensating boluses were able to provide superior dose uniformity to those of uniform thickness and the custom shielding adequately attenuated the electrons to that of the standard lead shields.