Alam R, Ibbott G S, Pourang R, Nath R
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Med Phys. 1997 Dec;24(12):2043-54. doi: 10.1118/1.598119.
Task Group 23 of the AAPM Radiation Therapy Committee has produced a test package for verification of the accuracy of treatment planning for photon external beam therapy. The package includes measured fundamental beam data for 4 and 18 MV x rays, and 13 test cases with measured dose values at selected points, which serve as the reference for determination of calculated dose accuracy. Test cases include three square fields, two rectangular fields, a wedged field, a blocked field, and an irregular field, as well as cases of an off-center plane, source-to-SOURCE distance (SSD) variation, oblique incidence, and lung and bone inhomogeneities. This package was used to evaluate two treatment planning systems. Although average dose variations in most cases were less than 1%, maximum deviations up to 19% were observed in one planning system and up to 11% in the other. Dose deviations greater than 3% were observed for 51 of 532 points (in the 4 MV case) and for 124 of 586 points (in the 18 MV case). An additional component of the test package is an evaluation of radiological field width at different depths. The largest deviation for width was 17.4 mm for 4 MV and 9.1 mm for 18 MV. In 20% of the widths studied, the deviation observed was greater than 3 mm for the 4 MV case. In the 18 MV case 18% of the widths had deviations greater than 3 mm. Our data indicate that the accuracy of the two treatment planning systems tested here warrants improvement, even for simple treatment geometries involving photon beams, which are generally considered to be well understood. As one of the treatment planning systems is widely used in the US, it is concluded that the accuracy of the currently available commercial treatment planning systems is not adequate for achieving the generally stated goal of +/- 5% accuracy of dose delivery in radiation therapy. The AAPM Task Group 23 test package provides an extremely useful tool for a quantitative analysis of treatment planning systems for photon beam radiation therapy.
美国医学物理学家协会（AAPM）放射治疗委员会第23任务组已制定了一个测试包，用于验证光子外照射治疗计划的准确性。该测试包包括4兆伏和18兆伏X射线的测量基本射束数据，以及13个测试案例，这些案例在选定的点处有测量剂量值，作为确定计算剂量准确性的参考。测试案例包括三个方形射野、两个矩形射野、一个楔形射野、一个遮挡射野和一个不规则射野，以及偏心平面、源轴距（SSD）变化、斜入射以及肺部和骨骼不均匀性的案例。该测试包用于评估两个治疗计划系统。虽然大多数情况下的平均剂量变化小于1%，但在一个计划系统中观察到的最大偏差高达19%，在另一个系统中高达11%。在532个点中的51个点（4兆伏情况）和586个点中的124个点（18兆伏情况）观察到剂量偏差大于3%。测试包的另一个组成部分是对不同深度处放射野宽度的评估。4兆伏时宽度的最大偏差为17.4毫米，18兆伏时为9.1毫米。在4兆伏的案例中，在所研究的宽度中有20%观察到的偏差大于3毫米。在18兆伏的案例中，18%的宽度偏差大于3毫米。我们的数据表明，这里测试的两个治疗计划系统的准确性需要提高，即使对于涉及光子束的简单治疗几何形状也是如此，而这些通常被认为是已充分了解的。由于其中一个治疗计划系统在美国广泛使用，得出的结论是，目前可用的商业治疗计划系统的准确性不足以实现放射治疗中通常所说的剂量输送±5%准确性的目标。AAPM第23任务组测试包为光子束放射治疗的治疗计划系统的定量分析提供了一个极其有用的工具。
