Dosimetric effects of brass mesh bolus on skin dose and dose at depth for postmastectomy chest wall irradiation

Abstract

To investigate the feasibility of using the brass mesh bolus as an alternative to tissueequivalent bolus for post mastectomy chest wall cancer by characterizing the dosimetric effects of the 2-mm fine brass bolus on both the skin dose, the dose at depth and spatial distribution. Materials and methods: Surface dose and percent depth dose data were acquired for a 6 MV photon beam in a solid water phantom using MOSkin TM , Gafchromic EBT3 film and an Advanced Markus ionization chamber. Data were acquired for the case of: no bolus, Face-up bass bolus, Face-down brass bolus, double brass bolus, 0.5 cm and 1.0 cm of Superflab TE bolus. The exit doses were also measured via MOSkin TM dosimeter and Markus ionization chamber. Gafchromic EBT3 film strips were used to plot dose profile at surface and 10cm depth for Faceup brass, Face-down brass, double brass, 0.5 cm and 1.0 cm of Superflab TE bolus. Results: The surface dose measured via MOSkin TM dosimeter increased from 19.2 ± 1.0 % to 63.1± 2.1 % under Face-up brass discs, 51.2 ± 1.2 % under Face-up brass spaces, 61.5 ± 0.5 % under Face-down brass discs, and 41.3 ± 2.1 % under Face-down brass spaces. The percentage difference in the dose measured under brass discs between Face-up versus Face-down was less than 2 % for entrance dose and 10 % for exit dose, whereas the percentage difference under brass spaces was approximately 3 % for entrance dose and about 5 % for the exit dose. Gafchromic EBT3 film strip measurements show that the mesh bolus produced ripple beam profiles due to the mesh brass construction. Conclusions: Brass bolus does not significantly change dose at depth (less than 0.5 %), and the surface dose is increased similar to TE bolus. Considering this, brass mesh may be used as a substitute for TE bolus to increase superficial dose for chest wall tangent plans.

Surface Dose Measurements in Chest Wall Postmastectomy Radiotherapy to Achieve Optimal Dose Delivery with 6 MV Photon Beam

“…In our study, the application of brass mesh bolus was discontinued at 20 th fraction in patient's C01, C02, 23 rd fraction in a patient C17 and 21 st fraction in patient C26 since they developed Grade 2 skin toxicity (cumulated target dose was around 40–46 Gy). Al-Rahbi et al [ 20 ] reported similar Grade 2 reactions between the 18 th and 23 rd fractions (in the range 79.5% to 84.9% with the mean skin dose of 81.9%).…”

“…[ 15 ] Commercially available brass mesh bolus provides more chest wall conformity and has become popular in a few departments, and its benefits and surface dose estimates were highlighted in many reports. [ 16 17 18 19 20 21 ]…”

“…The dosimetric characterization of the use of brass mesh bolus, methods of surface dose estimates, and standardization of phantom techniques were reported. [ 20 22 ] The present study has objective to prospectively examine and quantify the surface dose to the chest wall using radiochromic EBT3 films in patients undergoing 3DCRT with 6 MV photon beam to standardize protocol for optimal skin dose to the chest wall.…”

Verification using in vivo optically stimulated luminescent dosimetry of the predicted skin surface dose in patients receiving postmastectomy radiotherapy

“…Behttps://doi.org/10.1016/j.meddos.2020.10.001 0958-3947/Crown Copyright © 2020 Published by Elsevier Inc. on behalf of American Association of Medical Dosimetrists. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) cause of this, there is variation in the use and type of bolus material among clinicians, [4][5][6] with bolus material removed following the onset of unacceptable acute toxicity. The chest wall is one of only a few remaining sites in which radiation dose is estimated clinically.…”

eXaSkin: A novel high-density bolus for 6MV X-rays radiotherapy

“…A possible alternative to Superflab is high-density brass mesh (brass density = 8.73 g/cm 3 ), which offers the advantage of superior conformity to the skin, especially in the presence of surface irregularities; because there are fewer air gaps, skin dose uniformity is superior [13][14][15]. It was shown that a 2-mm thick brass mesh does not significantly change dose at depth (< 0.5%), and that skin dose increases, but less than with a 0.5-cm and 1.0-cm thick layer of Superflab [15]. Manger et al [14] reported that brass mesh might produce photoneutrons when irradiated with high-energy photon beams (15 MV, 24 MV), with a potential increase of effective dose to staff and patients.…”