George R E, Hartson-Eaton M
Int J Radiat Oncol Biol Phys. 1985 Jun;11(6):1221-4. doi: 10.1016/0360-3016(85)90073-2.
Beam quality, surface doses, depths of maximum dose, peak dose rates, beam profiles, and central axis percentage depth doses of a medical microtron's 21 MV photon beam were measured. The half-value layer of lead was 1.35 cm, the half-value layer of water was 23 cm, and the nominal acceleration potential was 17.7 MV. For a 10 X 10 cm2 field at 100 cm SSD, the maximum dose occurred at a depth of 3 g X cm-2 and the surface dose was 18% of the maximum. The highest dose rate at isocenter was approximately 800 cGy X min-1. The worst horns on beam profiles occurred at a depth of 5 cm for the 35 X 35 cm2 field where the dose rate 4 cm from the edge of the beam was 3% higher than that on the central ray. No horns were apparent for fields 25 X 25 cm2 or smaller.
对一台医用电子回旋加速器的21兆伏光子束的射束质量、表面剂量、最大剂量深度、峰值剂量率、射束轮廓以及中心轴百分深度剂量进行了测量。铅的半值层为1.35厘米，水的半值层为23厘米，标称加速电位为17.7兆伏。对于在100厘米源皮距下的10×10平方厘米射野，最大剂量出现在深度为3克·厘米⁻²处，表面剂量为最大剂量的18%。等中心处的最高剂量率约为800厘戈瑞·分钟⁻¹。对于35×35平方厘米射野，射束轮廓上最严重的“角”出现在深度5厘米处，在距射束边缘4厘米处的剂量率比中心轴上的剂量率高3%。对于25×25平方厘米或更小的射野，未观察到明显的“角”。
