Author: Rami M. Shorti, Gary R. Stinnett 👨🔬
Affiliation: Intermountain Health, Radiation Oncology, Intermountain Health, Advanced Visualization Engineering Department 🌍
Purpose: In this work we present the workflow, materials analysis, and lessons learned from leveraging advanced 3D printing Polyjet Technology to print conformal bolus for radiation therapy.
Methods: Patients undergo an initial CT scan to delineate the treatment area. Using Eclipse, an initial bolus contour is generated. The contour is exported as a DICOM structure set and converted into a 3D printable STL file using 3DSlicer. The STL file is then refined using Meshmixer to ensure no sharp edges and localized smoothing. Once validated against the CT, the design is prepared for production using GrabCAD Pro slicer software and printed on a J850 Digital Anatomy 3D Printer. Various resin-based photopolymer Polyjet 3D print materials are used. Post-printing, the bolus is cleaned and smoothed by hand. The patient then undergoes simulation with the 3D printed bolus. HU measurements are taken in Eclipse and air gap measurements are recorded using Aria’s offline review tool.
Results: Ten boluses have been printed for treatment sites on the nose, scalp, and ear. 3D printed bolus was also used as an applicator for nose brachytherapy with hollow channels for needles. Average HU measurements of the printed bolus shows that the material prints uniformly within single prints and is consistent across multiple prints. Air gaps for rigid versus flexible nose bolus were evaluated, with rigid bolus having a smaller maximum gap.
Conclusion: This work presents the materials, workflow, and lessons learned from implementing 3D-printed bolus in our clinic. The Polyjet 3D printed material prints uniformly and consistently. Comparing flexible vs. solid bolus, we found solid bolus provided the most repeatable setup for nose and ear treatments. Both flexible and solid bolus performed equally well for scalp treatment sites. Rigid bolus was chosen for brachytherapy applicators due to concerns about dosimetric differences from applicator stretching.