Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia; Radiotherapy Department, National Oncology Center, The Royal Hospital, Muscat, Oman.
Centre for Medical Radiation Physics (CMRP), University of Wollongong, Australia; St George Cancer Care Centre, St George Hospital, Kogarah, Australia.
Phys Med. 2018 Oct;54:84-93. doi: 10.1016/j.ejmp.2018.09.009. Epub 2018 Oct 2.
To investigate the feasibility of using the brass mesh bolus as an alternative to tissue- equivalent 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.
Surface dose and percent depth dose data were acquired for a 6 MV photon beam in a solid water phantom using MOSkin™, 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™ dosimeter and Markus ionization chamber. Gafchromic EBT3 film strips were used to plot dose profile at surface and 10 cm depth for Face-up brass, Face-down brass, double brass, 0.5 cm and 1.0 cm of Superflab TE bolus.
The surface dose measured via MOSkin™ 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.
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.
通过研究 2mm 精细黄铜 bolus 在皮肤剂量、深度剂量和空间分布方面对术后胸壁癌症的剂量学影响，探讨将黄铜网 bolus 用作组织等效 bolus 替代品的可行性。
在固体水模体中，使用 MOSkin™、Gafchromic EBT3 胶片和 Advanced Markus 电离室，对 6MV 光子束的表面剂量和百分深度剂量数据进行采集。采集的数据包括：无 bolus、朝上的 Bass bolus、朝下的 brass bolus、双 brass bolus、0.5cm 和 1.0cm 的 Superflab TE bolus。通过 MOSkin™剂量仪和 Markus 电离室测量出口剂量。使用 Gafchromic EBT3 胶片条绘制朝上的 brass、朝下的 brass、双 brass、0.5cm 和 1.0cm 的 Superflab TE bolus 的表面和 10cm 深度处的剂量分布。
通过 MOSkin™剂量仪测量的表面剂量在朝上的 brass 圆盘下从 19.2±1.0%增加到 63.1±2.1%，在朝上的 brass 空间下从 51.2±1.2%增加到 61.5±0.5%，在朝下的 brass 圆盘下从 61.5±0.5%增加到 41.3±2.1%，在朝下的 brass 空间下从 41.3±2.1%增加到 61.5±0.5%。 brass 圆盘下入口剂量的 brass 圆盘与 brass 圆盘之间的剂量差异百分比小于 2%，出口剂量的差异百分比小于 10%，而 brass 空间下入口剂量的差异百分比约为 3%，出口剂量的差异百分比约为 5%。Gafchromic EBT3 胶片条测量显示，由于网孔 brass 结构，网孔 bolus 产生了波纹束轮廓。
brass bolus 不会显著改变深度剂量（小于 0.5%），并且表面剂量增加类似于 TE bolus。考虑到这一点，brass mesh 可以用作 TE bolus 的替代品，以增加胸壁切线计划的表面剂量。
