Sastre-Padro Maria, Lervåg Christoffer, Eilertsen Karsten, Malinen Eirik
Department of Medical Physics, Division of Cancer Medicine and Radiotherapy, Rikshospitalet University Hospital, Oslo, Norway.
Med Dosim. 2009 Fall;34(3):202-6. doi: 10.1016/j.meddos.2008.08.005. Epub 2008 Sep 21.
The performance of 3 multileaf collimator (MLC) systems (Varian Medical Systems, Elekta, and Siemens Medical Solutions) mounted on 7 different radiotherapy linear accelerators was investigated by a stripe test. The stripe test consisted of 8 adjacent multileaf segments of 2.5 x 40 cm(2), enclosed by all leaf pairs. With 6-MV photons, the segments were used to irradiate Agfa CR films. The optical density profile of the irradiated film in the travel direction of the MLC was used to estimate the short- and long-term leaf positioning reproducibility. The short-term reproducibility was found by analyzing 6 consecutive stripe tests. The long-term reproducibility was obtained by performing 3 to 5 stripe tests over 2 months. The short-term reproducibility was mainly within 0.3 mm for all systems. For the long-term reproducibility, the Varian and Elekta MLCs were within 0.4 to 0.5 mm, while the Siemens MLC showed a wider distribution, with values up to 1 mm for some leaf pairs. The inferior long-term reproducibility of the Siemens MLCs was mainly due to a decrease of the segment size with time. In conclusion, the stripe test is a useful method for evaluating MLC performance. Furthermore, the long-term reproducibility varied among the MLC systems investigated.
通过条纹测试研究了安装在7台不同放射治疗直线加速器上的3种多叶准直器（MLC）系统（瓦里安医疗系统公司、医科达公司和西门子医疗解决方案公司）的性能。条纹测试由8个相邻的2.5×40 cm²多叶段组成，由所有叶对包围。使用6兆伏光子，这些段用于照射爱克发CR胶片。利用照射胶片在MLC行进方向上的光学密度分布来估计叶片定位的短期和长期重复性。通过分析6次连续的条纹测试来发现短期重复性。通过在2个月内进行3至5次条纹测试来获得长期重复性。所有系统的短期重复性主要在0.3毫米以内。对于长期重复性，瓦里安和医科达的MLC在0.4至0.5毫米以内，而西门子的MLC显示出更宽的分布，一些叶对的值高达1毫米。西门子MLC较差的长期重复性主要是由于段尺寸随时间减小。总之，条纹测试是评估MLC性能的一种有用方法。此外，在所研究的MLC系统中，长期重复性有所不同。
