Design, Fabrication, and Validation of 3D Printed, Patient-Specific Compensators for Postmastectomy Radiation Therapy

The purpose of this study was to use 3D printed, patient-specific tissue compensators to overcome the 3D planning limitations for postmastectomy radiation therapy (PMRT). Tissue compensators can be used to reduce dose heterogeneity, hot and cold spots at field junctions, and treatment complexity, but are currently seldom used due to the difficulty in designing, fabricating, and validating them. To produce compensators using 3D printing technology, suitable materials had to be found and characterized. Several materials were found to be promising, but previously unreported material uncertainties were also discovered that must be carefully controlled for in 3D printing studies. A new algorithm was also created to optimally design the compensator shape to conform the dose to the desired region, while maintaining acceptable geometric considerations for 3D printing. Patients’ dose distributions calculated using this algorithm were superior to dose distributions calculated in those same patients using more conventional matched field plans. To validate the idealized dose distributions, a new technique was developed to 3D print patient-specific, large scale radiotherapy phantoms with dosimeters throughout that can accurately reflect patients’ anatomy better than generalized phantoms. Six of these phantoms were created for a sample of patients with a range of body vi sizes. A sample of compensators was designed and printed for these novel phantoms, and radiation doses were measured and compared to planned dose distributions. Measured doses agreed well with planned doses. This study demonstrates that 3D printed, patient-specific compensators can be used to simplify treatments, and improve dose distributions in PMRT patients relative to their conventional 3D plans. Additionally, the algorithm could be applied to calculate compensators for different treatment sites in the future, and the phantoms developed could be used to perform pseudo in vivo dosimetry measurements for a wide range of radiotherapy experiments