Lane K, Bloch P, Davis L W
Am J Roentgenol Radium Ther Nucl Med. 1974 Aug;121(4):865-72. doi: 10.2214/ajr.121.4.865.
Calculation of isodose patterns for high energy therapy units using Cunningham's BEAM program requires accurate information on the beam profile in air. This may be obtained by scanning across the x-ray beam using a very small silicon diode detector. Data obtained on a particular unit may not be applicable to any other unit. Computer calculations of isodose curves for high energy x-ray machines must use a 0.25 cm. or smaller lateral grid of dose calculation points to ensure accurate reproduction of the sharp fall-off of the dose at the beam edge. Computer calculation time to obtain the isodose curves using this size lateral grid is prohibitively long. The computing time can be appreciably reduced by: (1) changing the width of the annular sectors used in calculating the contribution of scattered radiation to the dose to 0.5 cm.; and (2) calculating the dose at 0.25 cm. lateral intervals within 1 cm. of the beam edge, but changing the spacing of the grid to 1 cm. inside the field. These programming strategies do not produce any significant change in the isodose curves but lead to a significant reduction in computer time.
使用坎宁安的BEAM程序计算高能治疗设备的等剂量分布模式，需要关于空气中射束剖面的准确信息。这可以通过使用非常小的硅二极管探测器扫描X射线束来获得。在特定设备上获得的数据可能不适用于任何其他设备。高能X射线机等剂量曲线的计算机计算必须使用0.25厘米或更小的横向剂量计算点网格，以确保准确再现射束边缘剂量的急剧下降。使用这种尺寸的横向网格获得等剂量曲线的计算机计算时间长得令人望而却步。通过以下方法可以显著减少计算时间：（1）将用于计算散射辐射对剂量贡献的环形扇区宽度改为0.5厘米；（2）在射束边缘1厘米范围内以0.25厘米的横向间隔计算剂量，但在场内将网格间距改为1厘米。这些编程策略不会对等剂量曲线产生任何显著变化，但会显著减少计算机时间。
