Lam K S, Lam W C
Med Phys. 1984 Jan-Feb;11(1):61-4. doi: 10.1118/1.595453.
For the Clinac 4, open field profiles measured in the principal plane have higher intensity "horns" than those in off-axis planes. The maximum deviation occurs at 1-cm depth, where in the worst case of large field sizes and off-axis distances the deviation can be as high as 16% in the region near the horns. A model is proposed to generate open field beam profiles in off-axis planes, based on measured profiles in the transverse principal plane and in the largest field size diagonal plane of the machine. Within the central 90% portion of the field, the maximum deviation of the generated profiles from the measured ones at the same off-axis distance varies from about 3% at 1-cm depth to about 2% at 13-cm depth and then increases to less than 5% at 25-cm depth, even for very large field sizes and off-axis distances. Very little additional computer time and data storage are required for this procedure. Using these profiles, the Milan and Bentley method can be extended to three-dimensional treatment planning with good accuracy.
对于Clinac 4，在主平面测量的开放野轮廓比在离轴平面的轮廓具有更高强度的“角”。最大偏差出现在1厘米深度处，在大射野尺寸和离轴距离的最坏情况下，在角附近区域偏差可高达16%。提出了一种基于在机器的横向主平面和最大射野尺寸对角线平面测量的轮廓来生成离轴平面开放野射束轮廓的模型。在射野中心90%的区域内，对于相同的离轴距离，生成的轮廓与测量轮廓的最大偏差在1厘米深度处约为3%，在13厘米深度处约为2%，然后在25厘米深度处增加到小于5%，即使对于非常大的射野尺寸和离轴距离也是如此。此过程只需要很少的额外计算机时间和数据存储。使用这些轮廓，米兰和本特利方法可以扩展到具有良好精度的三维治疗计划。
