Tatcher M, Bjarngard B E
Department of Radiation Oncology, Roger Williams Medical Center, Brown University, Providence, Rhode Island 02908.
Med Phys. 1993 Jan-Feb;20(1):205-6. doi: 10.1118/1.597087.
Head-scatter factors were measured for a range of field sizes of rectangular shape from a linear accelerator that provides 6 and 25 MV photon beams. For a given field length and width, exchange of the inner and outer collimator pairs produces differences in the head-scatter factor of up to about 2% and 3% in open and wedged fields, respectively. Dependence on elongation deviates by up to 2% from that given by the equivalent squares. Such effects can easily be taken into account by using head-scatter data that have been directly measured in rectangular fields or by applying empirical corrections to values for square or equivalent square fields.
对头散射因子进行了测量，测量对象是一台能提供6兆伏和25兆伏光子束的直线加速器产生的一系列矩形野尺寸。对于给定的野长和野宽，内、外准直器对的互换在开放野和楔形野中分别会使头散射因子产生高达约2%和3%的差异。对头散射因子与伸长率的相关性与等效方野的情况相比偏差高达2%。通过使用在矩形野中直接测量的头散射数据，或对方野或等效方野的值应用经验校正，可以很容易地考虑到这些影响。
