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Dosimetric Comparison Between Two Different 3D Printed Bolus Materials for Electron Therapy of the Nose

D Vile

D Vile1*, B Overshiner2 , H Ai1 , P Yearling3 , (1) Indiana University, Indianapolis, IN, (2) Indiana University Health, Indianapolis, IN, (3) Indiana University Purdue University Indianapolis, Indianapolis, IN


SU-I-GPD-T-72 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: To investigate the dosimetric differences between materials in a custom 3D printed nose bolus.

Methods: The andromorphic Rando phantom was scanned using a handheld 3D optical surface scanner to get a surface rendering of the phantom head. From this scan, a custom bolus was designed to fit over the patient nose with a flat outer surface. The bolus was 3D printed using two different materials, a rigid acrylonitrile butadiene styrene (ABS), and a rubber-like PolyJet photopolymer material (Stratasys, Eden Prairie, MN). The two boluses were placed on the phantom and a CT scan was performed using a clinical protocol. The scans were imported into a treatment planning system, where identical en face electron beams were placed and calculated. The CT scans were analyzed for goodness of fit as well as dosimetric differences.

Results: From the surface scan, the two prints were successfully created using the same bolus model. From the CT scan, the ABS had a mean CT number of -78±9 HU of and the PolyJet had a mean of 119±10 HU. Qualitatively, the PolyJet gave a better fit along on the nose, with a smaller air gap present between the nose and the bolus, most likely due to the more flexible nature of the material. Consequently, the 90% isodose curve for the PolyJet material was slightly smoother. Isodose volumes were smaller for the PolyJet bolus, most likely due to the higher CT number composition.

Conclusion: Using a handheld 3D scanner, a custom bolus was created for the Rando phantom using two different materials. The less rigid PolyJet material gave a better fit to the phantom, but the higher CT numbers created smaller isodose volumes.

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