Program Information
Use of Tennis Racket and Air Gap Between the Body and Carbon Fiber Couch for Skin Sparing in Radiation Therapy of Prone Breast
E Lief*, Marsden Medical Physics Associates, Pelham, NY
Presentations
SU-E-T-777 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To reduce the skin dose from the carbon fiber couch scatter in radiation treatment of breast cancer in the prone position. If this issue is not addressed, the prone breast touching the solid carbon fiber couch can absorb significant dose to the skin and cause the skin reaction.
Methods: 1. Use of “tennis racket” instead of the solid couch. To check this hypothesis, we measured the dose at the depth of 5 mm in solid water phantom placed on the couch, using a Farmer chamber. A plan for a patient with 6MV beams, gantry angles of 113 and 286 degrees Varian scale was used. It was found that treatment with “tennis racket” instead of the solid carbon fiber couch reduces the surface dose by 5-7%, depending on the beam direction. 2. Use of the air gap between the couch and the body was analyzed using radiochromic film on the surface of the solid water phantom 10 cm thick. Initially the phantom was placed on the couch with the film sandwiched in between. Two fields at the angles of 135 and 315 degrees were used. The measurements were repeated for the air gap of 2 and 5 cm and 6 and 15 MV beams.
Results: It was found that a 2-cm gap decreased the surface dose by 3% for a 6 MV beam and by 5.5% for a 15 MV beam. A 5-cm gap reduced the dose by 9% for 6 MV and 13.5% for 15 MV.
Conclusion: Use of both methods (combined if possible) can significantly reduce the surface dose in radiation therapy of the prone breast and possible skin reaction. We plan to explore dependence of the dose reduction upon the angle of incidence.
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