Purpose: To develop and evaluate a source trajectory generation algorithm for 3D printed surface brachytherapy applicators that will mitigate the challenges of complicated manual design, technical skills needed for fabrication, and cost associated with production of traditional surface brachytherapy applicators.
Methods: The algorithm takes as input DICOM CT and RT structure data containing an applicator and body structures from the brachytherapy planning system. The patient side of the applicator is used to define equally-spaced contours perpendicular to the chosen direction of the source-trajectories to be generated. These contours are then offset into the applicator by a user-selected amount, thus providing a constant source-to-surface distance of trajectories to be created. To produce a constant inter-trajectory distance throughout a curved-surface of the applicator, a cut-plane is introduced that divides the offset contours into two groups which are then partitioned equally on both sides of the cut-plane. The partition increment determines the inter-trajectory distance and generates points on the offset contours which ultimately determine the source trajectories. Source trajectories are then subtracted from the applicator, forming catheter tunnels with a user-selected diameter. The result is exported in STL format, for 3D printing using an FDM approach. The algorithm was evaluated with regard to design and accuracy of fabrication.
Results: QA tests verified accuracy and consistency of source-to-surface and inter-trajectory distances to within +/- 0.5 mm throughout curved surfaces of realistic, patient-specific applicators. Experimentally, a catheter tunnel diameter of 3.2 mm was determined to be appropriate for a 6-French after-loading catheter type, using polylactic acid 3D printed test applicators, for tunnel radii of curvature as low as 13 mm.
Conclusion: This work offers an efficient and versatile method of design of surface brachytherapy applicators, providing a 3D printed device which production is accurate and reliable. The approach eliminates status-quo designs involving manual fabrication.
Funding Support, Disclosures, and Conflict of Interest: The main author of this publication is a full-time employee with the title of medical physicist specialist at Adaptiiv Medical Technologies, Inc. which fully funded the research presented within this e-poster.