SU‐E‐T‐19: A Comparison of the Dosimetric Effects of Brass Mesh and Superflab Boluses

Abstract

Purpose:We compared the dosimetric effects of brass mesh (Whiting and Davis, Attleboro Falls, MA) and Superflab (CNMC, Nashville, TN) boluses to verify equivalence between the two. Brass mesh bolus may be a convenient alternative to traditional bolus as it better conforms to the skin surface.Methods:Measurements were taken using a 6MV 10×10cm field produced by an Infinity linear accelerator (Elekta, Stockholm, Sweden) in a solid water phantom using a parallel plate ion chamber (Model 96035, Keithley Instruments, Cleveland, OH). Measurements compared 0.5cm and 1cm of Superflab to one to six layers of brass bolus mesh. Measurements were performed at depths from 0cm (‘skin’) to 10cm. Oblique beams were not studied.Results:Four layers of brass mesh were equivalent to 0.5cm Superflab within 5% at all depths. Six layers of brass compares most favorably with 0.5cm Superflab, with doses at all depths within 3%. Six layers of brass were not fully equivalent to 1cm Superflab, although the agreement was within 5% for depths greater than 3mm. Surface dose was 12% lower than 1cm Superflab. Surface dose can be up to 34% different between Superflab and brass mesh, but is less than 5% different with 4–6 layers of brass when compared to 0.5cm Superflab. To achieve surface dose agreement better than 5% compared to 1cm Superflab, more than 6 layers would be needed. The attenuation at depth was a maximum of 0.17cm per layer.Conclusion:Between four and six layers of brass mesh can be equivalent to 0.5cm Superflab, depending on the level of agreement desired. Equivalence within 5% at all depths to 1cm Superflab was not achieved even with six layers. This data agrees with measurements taken by Utsunomiya et al. (2010). More point measurements at shallower depths should be taken prior to clinical implementation of brass bolus mesh.