Intra-patient study comparing 3D printed bolus versus standard vinyl gel sheet bolus for postmastectomy chest wall radiation therapy

Publication date: Available online 24 December 2017
Source:Practical Radiation Oncology
Author(s): James L. Robar, Kathryn Moran, James Allan, James Clancey, Tami Joseph, Krista Chytyk-Praznik, R. Lee MacDonald, John Lincoln, Parisa Sadeghi, Robert Rutledge
PurposeThis patient study evaluated the use of 3D printed bolus for chest wall radiotherapy, with comparison to standard sheet bolus with regard to accuracy of fit, surface dose measured in vivo and efficiency of patient setup. By alternating bolus type over the course of therapy, each patient served as her own control.Methods and materialsFor sixteen patients undergoing chest wall radiotherapy, custom 5.0mm thick bolus was designed based on the treatment planning CT and 3D printed using polylactic acid (PLA). Cone beam CT was used to image and quantify the accuracy of fit of the two bolus types with regard to air gaps between the bolus and skin. As a QA measure for the 3D printed bolus, Optically Stimulated Luminescent Dosimetry provided in vivo comparison of surface dose at seven points on the chest wall. Durations of patient setup and image guidance were recorded and compared.ResultsIn 13 of 16 patients the bolus was printed without user intervention and the median print time was 12.6hours. The accuracy of fit of the bolus to the chest wall was improved significantly relative to standard sheet bolus with the frequency of air gaps 5mm or greater reduced from 30% to 13% (p<0.001), and maximum air gap dimension diminished from 0.5 +/− 0.3mm to 0.3 +/− 0.3mm, on average. Surface dose was within 3% for both standard sheet and 3D printed bolus. On average, the use of 3D printed bolus reduced the setup time from 104 to 76seconds.ConclusionsThis study demonstrates 3D printed bolus in post-mastectomy radiation therapy improves fit of the bolus and reduces patient setup time marginally compared with standard vinyl gel sheet bolus. The time savings on patient setup must be weighed against the considerable time for the 3D printing process.



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