Tissue Equivalence of Brass Mesh Bolus and Its Efficacy In Mitigating Loss of Skin Dose In the Presence of Skin–Bolus Air Gaps
Abstract
Purpose
To evaluate the dosimetric performance and surface conformality of a commercially available brass mesh bolus (BMB) compared with 3 mm Superflab (SF) in clinically realistic scenarios where air gaps are expected, such as in patients with tissue expanders.
Methods
Surface dose measurements were conducted using a PTW parallel plate chamber and Gafchromic EBT4 film on a breast phantom. Comparisons were made between BMB, SF, and solid water (SW) bolus materials. Treatment plans delivering 4005 cGy in 15 fractions were created in RayStation for both 3D conformal radiation therapy (3D-CRT) and volumetric-modulated arc therapy (VMAT). Dose was evaluated at six BB-marked locations across the breast phantom using film dosimetry and compared with RayStation-calculated doses with a 3 mm bolus.
Results
Ion chamber measurements under en face beams showed surface dose agreement within 2.8% across SW, SF, and BMB. Film-based dose measurements revealed that BMB and SF agreed within 15% at all points, with BMB yielding slightly higher surface doses at multiple locations, particularly in regions with air gaps. In VMAT plans, BMB provided an average of 3% higher surface dose compared to SF at BBs 1–4. BMB also demonstrated improved conformality over SF, particularly in inferior and medial regions.
Conclusion
BMB provides comparable surface dose to SF in both 3D-CRT and VMAT, with improved conformity on irregular surfaces. These findings support the clinical use of BMB as a practical alternative to SF in scenarios where air gaps may compromise consistent surface dose delivery.