Purpose: Secondary skin collimation is the optimal methodology for reducing electron scatter and preventing irradiation of non-involved tissue. However, the process of molds is cumbersome and commercial solutions are cost-prohibitive. We investigate the feasible clinical use of a 3D printed shaper filled with tungsten balls for skin collimation.
Methods: Using a 3D model a 3D printing based skin collimator (3D-SC) was produced. The thickness of the 3D-SC was set at 8 mm and filled with 2 mm tungsten balls (17.5 g/cm³). Measurements were performed with 6 MeV in solid water at 0.5 cm depth with Gafchromic™ EBT3 films. The film was irradiated with 300 MU. The irradiated film was scanned and analyzed with an OmniPro I’mRT (IBA Dosimetry). A clinical case is used to demonstrate the ease of implementation.
Results: The penumbra (90% to 20%) value measured was 0.175 mm for the 3D-SC. Compared to this, the conventional Cerrobend cut-out created 0.72 mm penumbra. The total print time of the 3D-SC was less than 5 hours. Once the CT scan was acquired, our clinical case was modeled in our 3D planning software within 30 minutes.
Conclusion: Skin collimation’s efficacy is confirmed with the 3D-SC. This process is efficient (e.g., less labor-intensive than molding), cost-effective, and the shielding (tungsten balls) is reusable. Future work will verify this methodology with additional patient cases involving large curvature and irregularity.