New technique for developing a proton range compensator with use of a 3-dimensional printer

Abstract

Purpose: A new system for manufacturing a proton range compensator (RC) was developed by using a 3-dimensional printer (3DP). The physical accuracy and dosimetric characteristics of the new RC manufactured by 3DP (RC_3DP) were compared with those of a conventional RC (RC_CMM) manufactured by a computerized milling machine (CMM).

Methods and materials: An RC for brain tumor treatment with a scattered proton beam was calculated with a treatment planning system, and the resulting data were converted into a new format for 3DP using in-house software. The RC_3DP was printed with ultraviolet curable acrylic plastic, and an RC_CMM was milled into polymethylmethacrylate using a CMM. The inner shape of both RCs was scanned by using a 3D scanner and compared with TPS data by applying composite analysis (CA; with 1-mm depth difference and 1 mm distance-to-agreement criteria) to verify their geometric accuracy. The position and distal penumbra of distal dose falloff at the central axis and field width of the dose profile at the midline depth of spread-out Bragg peak were measured for the 2 RCs to evaluate their dosimetric characteristics. Both RCs were imaged on a computed tomography scanner to evaluate uniformity of internal density. The manufacturing times for both RCs were compared to evaluate the production efficiency.

Results: The pass rates for the CA test were 99.5% and 92.5% for RC_3DP and RC_CMM, respectively. There was no significant difference in dosimetric characteristics and uniformity of internal density between the 2 RCs. The net fabrication times of RC_3DP and RC_CMM were about 18 and 3 hours, respectively.

Conclusions: The physical accuracy and dosimetric characteristics of RC_3DP were comparable with those of the conventional RC_CMM, and significant system minimization was provided.