Ferreira I H, Dutreix A, Bridier A, Chavaudra J, Svensson H
EQUAL Measuring Laboratory, Service de Physique, Institut Gustave-Roussy, 39 rue Camille Desmoulins, 94805 Villejuif, France.
Radiother Oncol. 2000 Jun;55(3):273-84. doi: 10.1016/s0167-8140(99)00101-2.
ESTRO has set up a Quality Assurance network (EQUAL) to check the dose delivered on axis in reference and non-reference conditions for external radiotherapy. The external audits covered by the network are based on measurements made with mailed thermoluminescent dosimeters (TLD).
The TLD consist of LiF powder type DTL 937 read with a PCL 3 automatic TLD reader. The participating centres are instructed to deliver to the TLDs absorbed doses of 2 Gy calculated with the Treatment Planning System used in clinical routine. A maximum of three photon energies by participating centre have been checked with 10 on-axis points per beam. The quantities checked include the reference beam output, beam output variation with collimator opening, depth dose data and wedge transmission factor.
During the 1998 EQUAL programme 102 centres have been checked corresponding to 235 beams (28 (60)Co beams and 207 X-ray beams). About 3% of the outputs in reference conditions show deviations outside tolerance level (>+/-5%). A similar rate of deviation is noted for the percentage depth doses. A rate of deviation (6%) has been observed for the beam output variation (open and wedged beams) and the wedge transmission factor. The analysis of the results shows that for 24 out of the 102 centres, a deviation outside tolerance level is observed at least in one point, mainly for the large and rectangular field sizes and for the wedged beams.
The results for the EQUAL programme show the importance of a quality assurance network in Radiotherapy especially for the non reference points even if they are only located on the beam axis (In order to participate in this network, please contact EQUAL secretariat or download the attached application form ESTRO web site: Dr I.H. Ferreira or Mrs Aline Mechet, EQUAL-ESTRO, Physics Department, Institut Gustave-Roussy 39 Rue Camille Desmoulins, F-94805 Villejuif Cedex, France. e-mail:equal@igr.fr or http://www.estro.be/).
欧洲放射肿瘤学会（ESTRO）已建立了一个质量保证网络（EQUAL），用于检查外照射放疗在参考条件和非参考条件下射野中心轴上的剂量。该网络所涵盖的外部审核是基于使用邮寄热释光剂量计（TLD）进行的测量。
TLD由DTL 937型LiF粉末组成，使用PCL 3自动TLD读取器进行读取。参与的中心被要求使用临床常规使用的治疗计划系统计算出2 Gy的吸收剂量传递给TLD。每个参与中心最多检查三种光子能量，每束射线在中心轴上有10个测量点。检查的量包括参考射野输出剂量、射野输出剂量随准直器开口的变化、深度剂量数据和楔形滤过器传输因子。
在1998年的EQUAL计划中，检查了102个中心，对应235束射线（28束钴 - 60射线和207束X射线）。在参考条件下，约3%的输出剂量显示出超出公差水平的偏差（>+/-5%）。深度剂量百分比也有类似的偏差率。射野输出剂量变化（开放野和楔形野）和楔形滤过器传输因子的偏差率为6%。结果分析表明，在102个中心中的24个中心，至少在一个测量点观察到超出公差水平的偏差，主要出现在大野和矩形野尺寸以及楔形野的情况下。
EQUAL计划的结果表明了放疗中质量保证网络的重要性，特别是对于非参考点，即使它们仅位于射野中心轴上（若要参与此网络，请联系EQUAL秘书处或从ESTRO网站下载所附申请表：法国维勒瑞夫市卡米耶·德穆兰街39号古斯塔夫 - 鲁西研究所物理系EQUAL - ESTRO的I.H.费雷拉博士或阿琳·梅谢夫人，邮编F - 94805。电子邮件：equal@igr.fr或http://www.estro.be/）。
