Custom 3D-printed applicators for high dose-rate brachytherapy in skin cancer.

ABSTRACT PURPOSE This paper describes the protocol for the development of 3D-printed custom applicators in treating skin carcinoma, the evaluation of the materials used, and the methods for segmentation and rendering of the applicators. MATERIAL AND METHODS The segmentation and rendering process for the applicator had six phases: (i) determination of the volume of the lesion using a computed tomography (CT) scan; (ii) delineation of the patient surface, using the same CT images; (iii) creation of the applicator in the planner and segmentation of the mold; (iv) preliminary dosimetry and establishment of the route of the catheter from the brachytherapy unit; (v) creation of the 3D applicator using specialized software; and (vi) applicator printing. Following this process, the patient returned for a second CT to undergo the definitive dosimetry with the applicator in place. Radiation therapy was then administered. RESULTS We made a total of 16 applicators. Only three applicators had to be remade, two due to an error in the infill and the other due to incorrect catheter geometry. In all cases, correct coverage of the planning target volume was achieved with the prescribed isodose. CONCLUSIONS The creation of custom molds in plesiotherapy for skin cancer with 3D printing is feasible. Compared to manual methods, 3D printing increases precision in applicator geometry and optimization of the dosimetry.