Gagnon W F, Horton J L
Med Phys. 1979 Jul-Aug;6(4):285-90. doi: 10.1118/1.594583.
When there is an absence of scattering material adjacent to the skin on the exit side of a megavoltage beam the dose to the skin is less than would be calculated using depth dose tables or isodose distributions measured in "semi-infinite" phantoms. Ionization measurements using a thin-window parallel-plate chamber show that the dose at 4 mg/cm2 from the exit surface is 14% to 16% less for cobalt-60 gamma rays and about 8% less for 25-MV x rays compared to the dose with full backscatter. As the angle of incidence increases the skin dose increases due to radiation scattered toward the surface. A method for the calculation of skin doses from tangential therapy beams is described.
当兆伏级射束出射侧的皮肤附近不存在散射物质时，皮肤所受剂量低于使用深度剂量表或在“半无限”模体中测量的等剂量分布所计算出的剂量。使用薄窗平行板电离室进行的电离测量表明，与全反向散射时的剂量相比，对于钴 - 60伽马射线，在距出射表面4mg/cm²处的剂量低14%至16%，对于25兆伏X射线则低约8%。随着入射角增加，由于朝向表面散射的辐射，皮肤剂量会增加。本文描述了一种用于计算切线治疗射束皮肤剂量的方法。
