Wrede D, Tai D, Edwards F, Coffey C, Schroader K
Br J Radiol. 1979 May;52(617):398-404. doi: 10.1259/0007-1285-52-617-398.
Measurements of central ray tissue-air ratio (TAR) for 60Co for a large number of irregularly shaped fields typically encountered in the cancer clinic were compared with TAR values either calculated by the Clarkson method using scatter air ratios or obtained from tables of square field data using the area/perimeter approach. Irregular field shapes included the "L", pentagonal, rectangular, upper and lower mantle and split fields. Agreement between both calculational methods and direct measurement is within +/- 2% if careful attention is given to central ray position as affected by the proper use of off-centre ratios in air. In the case of 10 MV X-rays, eight randomly chosen irregular fields again yielded an average agreement between both methods of calculation and experimental data of less than 1% and an agreement of less than 0.5% between the A/P and Clarkson calculations.
针对癌症临床中常见的大量不规则形状射野，对60Co的中心轴组织空气比（TAR）测量值，与使用散射空气比通过克拉克森方法计算得出的TAR值，或使用面积/周长法从方形射野数据表中获取的TAR值进行了比较。不规则射野形状包括“L”形、五边形、矩形、上半环和下半环射野以及分割射野。如果在空气中正确使用偏心比时，仔细注意中心轴位置，两种计算方法与直接测量之间的一致性在±2%以内。对于10MV X射线，再次随机选择的八个不规则射野，两种计算方法与实验数据之间的平均一致性小于1%，面积/周长法与克拉克森法计算之间的一致性小于0.5%。
