Biggs P J
Phys Med Biol. 1984 Sep;29(9):1089-96. doi: 10.1088/0031-9155/29/9/005.
Electron beams are playing an increasing role in the areas of intraoral and intraoperative radiotherapy. Because of the way the electron beams are used in these two procedures, they are rarely incident normally on the surface of the tissue to be treated, but are inclined at some angle. Previous work has shown that when low-energy electron beams are used in this way, the per cent depth-dose curves, when measured along the oblique axis (the central axis of the beam) show a decrease compared with normal incidence. To quantify this effect in detail the per cent depth dose distributions of electron beams in the energy range 4-29 MeV have been studied as a function of their angle of incidence with respect to the normal (phi) between 0 and 60 degrees. The curves for different phi are compared by plotting the per cent depth dose along the central axis in each case: at low energies, this decreases as phi increases, while at the highest energies, the change is very small. The surface dose also changes, increasing with phi at low energies and decreasing at high energies.
电子束在口腔内放疗和术中放疗领域正发挥着越来越重要的作用。由于在这两种治疗过程中电子束的使用方式，它们很少垂直入射到待治疗组织的表面，而是以一定角度倾斜入射。先前的研究表明，当以这种方式使用低能电子束时，沿斜轴（电子束的中心轴）测量的百分深度剂量曲线与垂直入射相比会降低。为了详细量化这种效应，研究了能量范围在4 - 29 MeV的电子束的百分深度剂量分布随其相对于法线的入射角（φ）在0到60度之间的变化。通过绘制每种情况下沿中心轴的百分深度剂量来比较不同φ值的曲线：在低能量时，随着φ的增加百分深度剂量降低，而在最高能量时，变化非常小。表面剂量也会发生变化，在低能量时随φ增加，在高能量时随φ降低。
