Characterization of novel 3D‐printed metal shielding for brachytherapy applicators

Abstract

PurposeTo characterize 3D‐printed stainless steel metal samples in the presence of an Iridium‐192 source for organ‐at‐risk sparing in gynecologic brachytherapy.MethodsSamples of 3D‐printed stainless steel (5.5 × 5.5 cm2, thickness range 1–5 mm) were embedded in a solid water phantom at varying distances from source catheters. An Ir‐192 brachytherapy source was passed through the phantom and the dose was measured using EBT3 Gafchromic film. The film was initially positioned in the sagittal plane 2 cm away from the catheters, with the metal directly below and then 1 cm from the film. A uniform dose was delivered at the film plane. A second setup measured a depth dose curve in solid water with film in the transverse plane directly above the metal samples. This setup was recreated using Monte Carlo simulations (EGSnrc egs_brachy). Validation between methods was performed with unshielded (solid water only) measurements.ResultsThe planar dose passing through the metal samples (thickness 1–5 mm) at the midpoint between the film and catheters, decreased compared to solid water by 7.4% ± 6.9% to 26.5% ± 5.5%. Dose enhancement on the order of 5% was noted when metal was directly adjacent to the film. The average decrease in depth dose from a single dwell position ranged from 10.0% ± 5.9% (1 mm) to 21.1% ± 5.3% (5 mm) as measured with film, and from 3.8% ± 0.9% (1 mm) to 16.3% ± 0.9% (5 mm) using MC simulation. The average depth dose values were measured using a line width of 2.5 mm for film, and 3 mm for MC simulation, and the measurements generally agree within standard error.ConclusionsThe 3D‐printed metal samples show potential for personalized applicators. Maximum dose reduction of 26.5% ± 5.5% compared to solid water was measured at 2 cm from the source using the 5 mm sample. An outer layer of solid water could potentially be used to reduce dose enhancement due to increased scatter near the metal.