Validation of a 3D printed bolus for radiotherapy: a proof-of-concept study

3D-printed boluses in radiation therapy are of increasing interest for enhancing treatment precision and patient comfort. A comprehensive clinical validation of these boluses remains to be established. This study aims to confirm the effectiveness of a 3D-printed bolus through a proof-of-concept comparative validation, by implementing in a clinical setting a bolus made of PLA and designed to ensure uniform dose coverage for a case in the eye region. In this study the 3D-printed bolus was compared to two commercially available boluses (one thermoplastic and one skin type) by using a refecence where no bolus was present (with the optimal dose distribution scenario). All boluses were placed on an anthropomorphic head phantom and BeOSL detectors were used to measure dose values to determine the level of their effectiveness on delivery. During the scanning process, a thermoplastic mask was used to prevent bolus movement and to accurately reproduce clinical scenarios. Differences in dose values at D_maxand D_50%revealed the performance of each bolus. The treatment planning system (TPS) and BeOSL readings for the 3D printed bolus were within 2% (the clinical tolerance), with 0.66% dose difference for the customized 3D-printed bolus. Although the thermoplastic bolus had the closest value to the detector reading, with a score of 0.30%, this result was influenced by improper shaping of the bolus on the phantom and the presence of a wide air gap, which caused lack of eye covering. Whereas, the skin bolus, due to higher volume of air between phantom surface and bolus, showed a 1.29% dose difference between the TPS values and the OSL detector readings. We provide a comparative validation for the use of 3D printed boluses and highlight that proper bolus fitting is essential in clinical settings to avoid air gaps and to maintain dose distribution over multiple treatment sessions.