A Rapid Prototyping Strategy for Manufacturing of Personalized Bolus

In radiotherapy, the treatment of skin tumors requires the application of tissue-equivalent devices in order to avoid the skin-sparing effect, and thus maximize and equalize the dose on the target. In the common clinical practice these devices, called bolus, are standard pads that do not perfectly adapt to the geometry of the patient generating empty spaces at the skin-bolus interface. This phenomenon hinders an efficient planning of the dose to be administered due to the non-adherence and the unpredictability of the position of the air gaps. In this work a workflow for the production of patient-specific bolus in Ecoflex® 00–10 silicone rubber (soft, biocompatible and sterilizable material) is proposed. The process exploits modern Reverse Engineering and Additive Manufacturing technologies to guarantee an accurate compliance with the involved geometries. Significant improvement, with respect to flat boluses, in the adhesion of the medical device to the anatomical region were found through in-vitro testing using replicas of the involved anatomy. Repeatability tests of the positioning performed on the customized bolus led to satisfying results demonstrating the possibility of accurate and predictable treatment planning.