Klinik für Radio-Onkologie, Kantonsspital St. Gallen, Switzerland.
Med Phys. 2010 Aug;37(8):4424-31. doi: 10.1118/1.3460795.
In 2008, a national intensity modulated radiation therapy (IMRT) dosimetry intercomparison was carried out for all 23 radiation oncology institutions in Switzerland. It was the aim to check the treatment chain focused on the planning, dose calculation, and irradiation process.
A thorax phantom with inhomogeneities was used, in which thermoluminescence dosimeter (TLD) and ionization chamber measurements were performed. Additionally, absolute dosimetry of the applied beams has been checked. Altogether, 30 plan-measurement combinations have been used in the comparison study. The results have been grouped according to dose calculation algorithms, classified as "type a" or "type b," as proposed by Kntis et al. ["Comparison of dose calculation algorithms for treatment planning in external photon beam therapy for clinical situations," Phys. Med. Biol. 51, 5785-5807 (2006)].
Absolute dosimetry check under standard conditions: The mean ratio between the dose derived from the single field measurement and the stated dose, calculated with the treatment planning system, was 1.007 +/- 0.010 for the ionization chamber and 1.002 +/- 0.014 (mean+/- standard deviation) for the TLD measurements. IMRT Plan Check: In the lung tissue of the planning target volume, a significantly better agreement between measurements (TLD, ionization chamber) and calculations is shown for type b algorithms than for type a (p <0.001). In regions outside the lungs, the absolute differences between TLD measured and stated dose values, relative to the prescribed dose, [(Dm-Ds)/Dprescribed], are 1.9 +/- 0.4% and 1.4 +/- 0.3%, respectively. These data show the same degree of accuracy between the two algorithm types if low-density medium is not present.
The results demonstrate that the performed intercomparison is feasible and confirm the calculation accuracies of type a and type b algorithms in a water equivalent and low-density environment. It is now planned to offer the intercomparison on a regular basis to all Swiss institutions using IMRT techniques.
2008 年，对瑞士所有 23 家肿瘤放疗机构进行了全国调强放射治疗（IMRT）剂量学比对。其目的是检查以计划、剂量计算和照射过程为重点的治疗链。
使用具有不均匀性的胸部体模，进行了热释光剂量计（TLD）和电离室测量。此外，还检查了应用光束的绝对剂量。在比较研究中总共使用了 30 个计划-测量组合。结果根据剂量计算算法进行分组，分为“类型 a”或“类型 b”，如 Kntis 等人所提出的。["比较治疗计划中光子外照射治疗剂量计算算法的临床情况，"Phys。Med。Biol. 51, 5785-5807（2006）]。
标准条件下的绝对剂量检查：从单个场测量得出的剂量与治疗计划系统计算的剂量的比值，对于电离室为 1.007 +/- 0.010，对于 TLD 测量为 1.002 +/- 0.014（平均值+/-标准差）。IMRT 计划检查：在计划靶区的肺组织中，与类型 a 相比，类型 b 算法的测量（TLD、电离室）与计算之间的一致性明显更好（p <0.001）。在肺外区域，TLD 测量值与规定剂量值的绝对差值，相对于规定剂量，[（Dm-Ds）/Dprescribed]，分别为 1.9 +/- 0.4%和 1.4 +/- 0.3%。如果不存在低密度介质，则这些数据表明两种算法类型具有相同的精度。
结果表明，所进行的比对是可行的，并证实了在水等效和低密度环境中类型 a 和类型 b 算法的计算精度。现在计划定期向所有使用调强放射治疗技术的瑞士机构提供比对。
