SU-E-T-437: Dosimetric Assessment of Brass Mesh Bolus for Postmastectomy Chest Wall Irradiation
- University of California, San Diego, La Jolla, CA (United States)
Purpose: It has been suggested that the use of a brass mesh bolus for chest wall irradiation sufficiently increases surface dose while having little effect on the dose at depth. This work quantified the increase in surface dose when using a brass mesh bolus in postmastectomy chest wall radiotherapy compared to tissue-equivalent bolus and assessed its effect on dose at depth. Methods: Percent depth doses with brass bolus, 5mm tissue-equivalent bolus, and no bolus were determined for a 6 MV photon beam in a solid water phantom using a parallel plate ionization chamber. Gafchromic film was used to determine the surface dose for the same three experimental setups. For comparison to a realistic treatment setup, gafchromic film and OSLDs were used to determine the surface dose over the irradiated area of a 6 MV chest wall plan with tangential beams delivered to a heterogeneous thorax phantom. The plan was generated using a CT of the phantom and delivered using brass mesh bolus, 5mm tissue-equivalent bolus, and no bolus. Results: For the en face beam, the central surface dose increased to 90% of maximum with the tissue-equivalent bolus, but to only 62% of maximum with the brass mesh. Using tangential beams on the thorax phantom, the surface dose increased from 40–72% to 75–110% of prescribed dose, with the brass mesh, and to 85–109% with the tissue-equivalent bolus. At depths beyond dmax in the plastic water phantom, the dose with and without brass mesh bolus differed by less than 0.5%. Conclusion: A brass mesh may be considered as a substitute for tissue-equivalent bolus to increase the superficial dose of 6 MV chest wall tangent plans. The brass mesh does not significantly change the dose at depth, so a non-bolus plan could be used for bolus and non-bolus treatments.
- OSTI ID:
- 22369588
- Journal Information:
- Medical Physics, Vol. 41, Issue 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-2405
- Country of Publication:
- United States
- Language:
- English
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