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Dosimetric Assessment of Transparent Polymer-Gel Type Bolus for Commonly Used Breast Treatment Delivery Techniques

D Fiedler*, S Hoffman, J Roeske, H Kang, Loyola Univ Medical Center, Maywood, IL

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: Skin dose enhancements of a recently developed transparent polymer-gel bolus (PGB) was assessed to allow for easier tattoo discernment and simplified patient setup. PGB was compared to superflab and brass mesh (BM) bolus for clinically relevant breast treatment delivery techniques.


Methods: Three breast treatment plans were generated on CT scans of a chest phantom; tangential step-and-shoot 3D conformal (3DCRT), tangential sliding-window 3DCRT, and volumetric modulated arc therapy (VMAT) with two 180° arcs. Skin doses of all three plans were measured with Gafchromic EBT3 films, separately delivered in triplicate. Each plan was delivered using BM (1 or 2 layers), PGB and superflab (3, 5, and 10mm each), as well as without bolus. Doses were determined by reading films with an Epson scanner using a calibration curve for each specific film batch with RIT software (Radiological Imaging Technology, CO, USA).


Results: For all plans with bolus, average skin doses measured between 92% and 107% of the prescription (Rx) dose. Without bolus, average skin dose measured between 51% and 65% of Rx dose. Surface doses observed with PGB were comparable to both superflab and BM. Concerning the three treatment delivery techniques, PGB resulted in average surface doses of 94.8%, 98.2% and 99.7% for 3, 5, and 10mm, respectively. Across all three treatment delivery techniques the cumulative average PGB skin values were within ±3% compared to expected values determined in the treatment planning system (TPS). BM and superflab measured values were within ±5% compared with expected values determined in TPS.


Conclusion: This study on skin dose with PGB and differing thicknesses of superflab and BM showed that PGB is a clinically equivalent bolus option for the 3, 5 and 10mm equivalent thicknesses available. We conclude that these PGB thickness options can be utilized accordingly instead of superflab or BM when transparency is needed.

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Keywords

Breast, Dose, Film

Taxonomy

TH- External Beam- Photons: General (most aspects)

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