Heukelom S, Lanson J H, Mijnheer B J
The Netherlands Cancer Institute, Amsterdam.
Radiother Oncol. 1994 Jan;30(1):66-73. doi: 10.1016/0167-8140(94)90011-6.
Wedge factors have been determined as a function of field size and phantom depth for a 60Co gamma-ray beam and X-ray beams in the range from 4 MV to 25 MV. The results show an increase of the wedge factor with field size, up to 9.1% for the 25 MV X-ray beam. The magnitude of this increase is a linear function of the product of that part of the irradiated wedge volume that can be observed from the point of measurement, its mass energy-absorption coefficient and mass density. This relationship is independent of the photon beam energy, the type of wedge material and the wedge angle. Differences in variation of the amount of backscatter to the monitor with field size for the open and wedged photon beam yielded only a minor influence, up to 0.7%. For the 4-16 MV X-ray beams the wedge factor increases linearly with phantom depth, almost independently of field size. For the 60Co gamma-ray beam and the 25 MV X-ray beam the wedge factor variation is a more complicated function of phantom depth for a particular field size.
已经确定了60Coγ射线束以及4MV至25MV范围内的X射线束的楔形因子与射野大小和模体深度的函数关系。结果表明，楔形因子随射野大小增加，对于25MV X射线束，增加幅度高达9.1%。这种增加的幅度是从测量点可观察到的被照射楔形体积部分与其质量能量吸收系数和质量密度乘积的线性函数。这种关系与光子束能量、楔形材料类型和楔形角无关。对于开放和楔形光子束，反向散射到监测器的量随射野大小的变化差异仅产生很小的影响，高达0.7%。对于4 - 16MV X射线束，楔形因子随模体深度线性增加，几乎与射野大小无关。对于60Coγ射线束和25MV X射线束，对于特定射野大小，楔形因子变化是模体深度的更复杂函数。
