Jani S K, Pennington E C, Wacha J E, Anderson K M
Division of Radiation Oncology, University of Iowa Hospitals and Clinics, Iowa City 52242.
Med Dosim. 1988;13(2):73-5. doi: 10.1016/0958-3947(88)90034-9.
The output (cGy/mu) of a rectangular field from a linear accelerator is not always the same as that of its equivalent square field. We have summarized output variations with upper and lower collimator setting for 4, 6, and 24 MV X-rays. It is concluded that an error in output on the order of a few percent is introduced for elongated fields if lower set of collimator jaws is used for setting the longer dimension of the field, and computing the output using equivalent square method. It is recommended that specific guidelines be developed regarding rectangular field setting on high energy linacs.
直线加速器矩形射野的输出剂量（cGy/mu）并不总是与其等效方形射野的输出剂量相同。我们总结了4、6和24MV X射线在上下准直器设置不同时的输出剂量变化。得出的结论是，如果使用准直器下叶设置射野的较长边长，并采用等效方形法计算输出剂量，对于狭长射野会引入百分之几的剂量误差。建议制定关于高能直线加速器矩形射野设置的具体指导原则。
