3D-Printing in Radiation Oncology: Development and Validation of Custom 3D-Printed Brachytherapy Alignment Device and Phantom

Brachytherapy seeks to treat cancer through insertion of radioactive sources aligned by needles within standardized blocking templates. However, many patients have anatomy that does not conform to standard tools. We created a 3D printed device to provide customized needle alignment for a patient. Device was validated through CT scan and treatment plan creation on a custom anatomical phantom based on patient data. CT scan of a cervix tumor from anonymized patient data was used to develop a 3D printed brachytherapy alignment tool and phantom anatomical mold. Multiple materials were evaluated to match patient anatomy in density and Hounsfield Units present on CT scan, with additional considerations for toxicity, compliance, and practicality. Alignment device and molds were developed in PLA. Silicone of T20 hardness was used to create relevant anatomical organs (Uterus, Rectum, Bladder). Tumor tissue was mimicked by addition of 1CC of Iodine contrast agent to silicone. Device and needles were arranged, inserted into anatomical phantom, and scanned by CT to mimic brachytherapy procedure. 3D printed Silicone uterus of 1.08 g/cm^3 and 40 HU mimicked human uterus on CT scan. Constructed uterus dimensions of 6.5 cm x 5.5 cm x 3.3 cm were verified on imaging to be within + 1 mm of original patient scan. The 1 CC of contrast agent provided sufficient differentiation of “tumor” ring from “tissue.” CT scan and treatment plan creation verified that the alignment device provided correction insertion of needles into the phantom tumor tissue and uterus. This pilot study provides a potential methodology to develop future anatomical phantoms and alignment devices from CT scans of patient data. Additional modifications could make this a viable training tool for future residents and medical students to learn brachytherapy. Key Points 3D printing can be leveraged to create a Brachytherapy alignment device from patient’s anatomy. Anatomical phantom can be generated from 3D printing for use testing device or for training. Relevant materials to create phantom that mimic patient’s anatomy on CT scan. Generation of a treatment plan based on CT scan was able to validate device and phantom