[Digital applicator by 3D printing in contact brachytherapy]

Brachytherapy of skin tumours uses custom applicators that are manufactured manually. The integration of 3D printing customization of applicators during hidh dose rate brachytherapy planning could allow a better skin conformation and a better reproducibility of the positioning and treatment. We present the technical implementation of this method for our first two patients. A provisional planning scanner was carried out to create a digital applicator. The creation of the digital applicator used successively several software programs. The first, commercial, was RhinocerosR 3D used via Grasshopper, an integrated open source plug-in. The 3D applicator was then exported to the commercial software Simplify3DR. A g-code format file was generated for the printer. A second scanner was made with a 3D applicator in place to plan the final treatment. The treatment was planned by reverse optimization. The applicator could be designed within 15 days. For patient A, it was noted that 95 % of the clinical target volume received at least 35.4Gy (63Gy EQD2). For patient B, 95 % of the clinical target volume received at least 36Gy (64.8Gy EQD2). The forecast and actual planimetry met the coverage criteria of D95. Contact brachytherapy with 3D bioimpression is feasible, after software training, for complex treatment lesions. This technique could be extended to other indications.