Mellenberg D E
University of Michigan, Ann Arbor 48109, USA.
Int J Radiat Oncol Biol Phys. 1995 Jul 15;32(4):1193-7. doi: 10.1016/0360-3016(94)00371-q.
To quantify the degradation of skin sparing associated with using beam modifiers such as compensators, immobilization devices, and custom blocks for high energy photon beams.
The degradation of skin sparing was quantified by measuring dose build-up curves with an extrapolation chamber for 6 and 15 MV photon beams. Uniform thickness compensators made of gypsum and lead, thermoplastic mask material, immobilization cradle foam, and cerrobend custom blocks were placed in geometries that mimic relevant clinical situations.
Compensators, whether made of gypsum or lead, placed in the linear accelerator's wedge slot did not significantly effect the depth dose curve's build-up region. Immobilization devices such as cradle foam or thermoplastic placed in contact with the patient degrade the skin sparing expected from high energy photon beams proportional to their thickness and density. Measurements behind custom blocks show that surface and near surface doses for a blocked field are best described by build-up curves for an equivalent size open field.
These results allow explanation and possibly prediction of skin reactions on patients in which compensators, foam immobilization cradles, thermoplastic masks, or custom blocks are used. These results also provide a baseline by which substitute materials can be evaluated.
量化与使用补偿器、固定装置和高能光子束定制挡块等射束修正器相关的皮肤保护的退化情况。
通过使用外推电离室测量6和15兆伏光子束的剂量积累曲线来量化皮肤保护的退化情况。将由石膏和铅制成的均匀厚度补偿器、热塑性面罩材料、固定托架泡沫和铈弯曲定制挡块放置在模拟相关临床情况的几何形状中。
放置在线性加速器楔形槽中的补偿器，无论由石膏还是铅制成，均不会显著影响深度剂量曲线的积累区域。与患者接触放置的固定装置，如托架泡沫或热塑性材料，会使高能光子束预期的皮肤保护效果退化，退化程度与它们的厚度和密度成正比。在定制挡块后面的测量表明，遮挡野的表面和近表面剂量最好用等效尺寸开放野的积累曲线来描述。
这些结果有助于解释并可能预测使用补偿器、泡沫固定托架、热塑性面罩或定制挡块的患者的皮肤反应。这些结果还提供了一个可用于评估替代材料的基线。
