Manufacturing and evaluation of multi-channel cylinder applicator with 3D printing technology

Introduction
This study was designed to assess dosimetric characteristics of 3D-printed personalized multi-channel cylinder applicator (MCCA).

Material and methods
UnionTech RS Pro 600 (UnionTech, Inc., Shanghai, China) 3D printer was used for manufacturing MCCA. The geometry of MCCA was designed with Fusion 360 v.2.0.5827 (Autodesk, Inc.) software. The designed file was exported to Meshmixer v.3.5 (Autodesk, Inc.) to create three-dimensional model in stereolithography (STL) file format, which is the common file format for inputting data to 3D printers. We used high-temp resin, FLHTAM02 model (Formlabs Inc., MA, USA), as material in 3D printing process. This resin model has good resistance to high temperature and compatibility with various solvents. We created a simple cubic shape phantom for dosimetric evaluation of the applicator with Gafchromic EBT3 films. Also, Monte Carlo method was applied to simulate MCCA in the same configuration as in experimental test.

Results
The mean ± standard deviation (SD) difference between measured and calculated doses in treatment planning system (TPS) for all control points was 0.0860 ±0.0393 Gy, corresponding to 4.01 ±1.21%. The mean ±SD difference between doses calculated by Monte Carlo simulation and TPS for all control points was 0.0996 ±0.0471 Gy, corresponding to 4.58 ±1.05%. The mean ±SD of dose difference between film measurement and Monte Carlo simulation for all control points was 0.0136 ±0.0200 Gy, corresponding to 0.60 ±0.69%. P-value for dose difference between film measurement and TPS, Monte Carlo and TPS, and film measurement and Monte Carlo were 0.7, 0.66, and 0.95, respectively.

Conclusions
Dosimetric results and mechanical accuracy of MCCA show that high-temp resin with SLA 3D printing technique can be used for producing patient-specific MCCA in brachytherapy.