Smit K, Kok J G M, Lagendijk J J W, Raaymakers B W
Department of Radiotherapy, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands.
Phys Med Biol. 2014 Apr 7;59(7):1845-55. doi: 10.1088/0031-9155/59/7/1845. Epub 2014 Mar 14.
At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER™, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER™ reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER™ dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER™ data was caused by the noise in the film, indicating correct performance of the IC PROFILER™ in the transverse 1.5 T magnetic field.
在乌得勒支大学医学中心安装了一台MR直线加速器原型机。该系统由一台8兆伏的医科达直线加速器和一台1.5特斯拉的飞利浦磁共振成像系统组成。本文研究了多轴电离室阵列IC PROFILER™在1.5特斯拉磁场中的性能。研究了磁场对IC PROFILER™的再现性、剂量响应线性、脉冲率频率依赖性、电子设备功率、面板方向和电离室形状的影响。线性、再现性、脉冲率频率依赖性、面板方向和电离室形状不受磁场影响。当测量结果归一化到中心参考电离室时，测量可以不变地开始。电离室在磁场中的方向很重要，因此在比较或归一化来自几个不同轴的结果时必须小心。将IC PROFILER™剂量分布图与在MR直线加速器中同时获得的胶片剂量分布图进行了比较。胶片和IC PROFILER™数据之间的偏差是由胶片中的噪声引起的，这表明IC PROFILER™在横向1.5特斯拉磁场中性能正确。
