Dawson D J
Med Phys. 1978 Sep-Oct;5(5):439-42. doi: 10.1118/1.594508.
The effects of field elongation on the central-axis output at dmax and on the depth-dose curves for the 6-MV x rays from the Therac 6 linear accelerator are considered. These parameters are independent of the collimator angle for both square and elongated fields. The exchange of collimator pairs results in significant output differences but has a negligible effect on the depth-dose curves. Both the central-axis output at dmax and the depth-dose curves agree satisfactorily with the predictions of the equivalent-square technique. An alternative method of greater accuracy is also indicated for the prediction of central-axis outputs at dmax for elongated fields.
研究了射野伸长对Therac 6直线加速器6兆伏X射线在深度剂量最大值（dmax）处的中心轴输出以及深度剂量曲线的影响。对于方形和伸长射野，这些参数均与准直器角度无关。准直器对的更换会导致显著的输出差异，但对深度剂量曲线的影响可忽略不计。深度剂量最大值（dmax）处的中心轴输出和深度剂量曲线均与等效方技术的预测结果吻合良好。文中还指出了一种用于预测伸长射野在深度剂量最大值（dmax）处中心轴输出的精度更高的替代方法。
