Room: Davidson Ballroom A
Purpose: 3D-printed, patient-specific tissue compensators have the potential to be used for postmastectomy radiotherapy (PMRT) to improve dose distributions and simplify treatment planning and delivery. This study was designed to  determine the clinical suitability and reproducibility of commercial 3D printable materials,  write an algorithm to design patient specific compensator shapes to achieve clinical goals, and  validate calculated dose distributions with film and TLD measurements in 3D printed phantoms of PMRT patients.
Methods: Four materials were evaluated for print consistency, density, and HU. Percent depth doses (PDD) were measured for the two most promising materials to evaluate dose calculation accuracy in the plastics. An iterative algorithm was developed to design a compensator shape for PMRT patients. The compensators were designed to fit into the electron aperture, with the cerrobend poured around it. Calculated dose distributions for compensator based plans were compared with clinical patients (multi-field, multi-energy) treatment plans. In particular, CTV coverage, lung dose, and heart dose were examined. Compensators were also designed for a set of 3D printed phantoms based on those same previous PMRT patients. These compensators were printed, and their associated treatment plans were delivered. Dose distributions were measured with film and TLD placed throughout the phantoms, and compared with the treatment planning system calculated dose distributions.
Results: Appropriate print protocols and material correction factors were determined for two materials to be used for clinical radiotherapy. The compensator based treatment plans had superior CTV coverage, and similar heart and lung doses to the conventional treatment plans. TLD doses agreed with calculated doses within 3%, and film profile measurements were accurate within 2 mm.
Conclusion: We have demonstrated that 3D-printed compensators make single-field electron therapy a clinically feasible treatment option for PMRT.