(Sunday, 7/14/2019)
Room: ePoster Forums
Purpose: To verify the dose delivered to the skin surface at which a breast makes contact with a prone breast board.
Methods: Due to the limited height of commercial breast boards, large or pendulous breasts may contact the bottom surface of the board. Our clinic traditionally traces these regions onto a sheet of paper to ensure reproducible setup. For this study, patient traces are copied onto a piece of radiochromic film that replaces the paper on a fraction with no pre-treatment imaging. Results are read out on Film QA Pro (Ashland Advanced Materials, Bridgewater, NJ) using the one scan technique and tri-color optimization. The film hotspot is identified and used to determine whether plan modifications are necessary to avoid excess skin toxicity due to loss of skin sparing at the skin/breast board interface. OSLDs were taped to the film to validate our method. Film was marked at corners of the OSLDs such that detector locations may be read out on film and compared directly to the OSLD readings. The test was performed eight times on six patients.
Results: OSLD readings agree with radiochromic film measurements to within their stated accuracy. Some error is expected in these readings since the film is in contact with the dosimeter instead of the breast itself. Pertinent information for the physician includes the average, maximum, and minimum doses received at the film interface. Future readings will not require OSLD verification, permitting the film to be free of opaque marks that confound dose readouts.
Conclusion: Physicians now have access to additional data to correlate skin toxicity with plans that deliver certain doses at the skin/breast board interface. Further work may include remodeling the effect of the prone breast board scatter in the treatment planning system. This new technique is now an established standard at our clinic.
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