Room: Karl Dean Ballroom A1
Purpose: To dosimetrically evaluate two daily bolus materials in an effort to standardize the use of chestwall bolus, increase efficiency, and reduce bolus application errors.
Methods: Chestwall treatments were simulated, planned, and delivered on a PIXY phantom (Radiology Support Devices, Inc., Long Beach, CA) with no bolus, 0.5 cm Superflab bolus, 1 layer of brass bolus, and 1 layer of wet chamois cloth bolus. 6 MV, 10 MV, and 15 MV plans were generated using a Philips Pinnacle TPS and delivered on Varian EX linear accelerators for each bolus option. OSLD measurements at 4 locations were taken for all bolus and energy combinations.
Results: No bolus and 0.5 cm Superflab bolus measurement results were combined to determine the surface dose equivalent to a treatment course of 16 fractions with 0.5 cm bolus and 12 fractions with no bolus. This bolus/no bolus combination represented current standard practice at our institution. The surface dose ranged from 69% to 81.1% of the prescribed dose for the bolus/no bolus regime, 75.8% to 85.2% for one layer of brass, and 68.2% to 82% for one layer of wet chamois cloth. As expected, measured surface doses decreased with beam energy in all cases.
Conclusion: Compared to a combination of 16 fractions with 0.5 cm Superflab bolus and 12 fractions with no bolus, daily application of wet chamois cloth bolus provides a comparable dose and daily application of brass bolus provides a slightly higher dose. The use of daily bolus increases standardization, increases planning and plan check efficiency, and reduces the opportunity for errors resulting from misapplication of bolus. Additionally, because of their smaller effective thickness, the daily bolus options would result in less perturbation to the surface dose and overall chestwall dose if a bolus application is inadvertently omitted compared to 0.5 cm thick bolus.
Breast, Surface Dose, In Vivo Dosimetry