Damrongkijudom N, Oborn B, Butson M, Rosenfeld A
Centre for Medical Radiation Physics, University of Wollongong, Australia.
Australas Phys Eng Sci Med. 2006 Dec;29(4):321-7. doi: 10.1007/BF03178398.
Electron contamination generated from interactions of x-rays with components in a medical linear accelerator's head can increase damage to skin and subcutaneous tissue during radiotherapy through increased dose deposition. Skin and subcutaneous dose from high energy x-rays can be reduced using magnetic fields to sweep the electron contamination away from the radiation treatment field. This work is aimed at investigating the magnetic fields generated by an improved magnetic deflector which utilizes Nd2Fe14B magnets. Magnetic field strengths generated by the deflector have been simulated using Vizimag 3.0 magnetic modelling software. The improved deflector has a more uniform magnetic field strength than its predecessor and is optimised to easily fit on a clinical linear accelerator. Experimental measurements of the magnetic field strengths produced have also been performed for comparison. Results show a relatively good match to Vizimag modelling in the central regions of the deflector. Reductions of skin and subcutaneous dose up to 34% of original values were seen for a 20 x 20 cm2 field at 6MV x-ray energy.
在医用直线加速器机头中，X射线与部件相互作用产生的电子污染会通过增加剂量沉积，在放射治疗期间加重对皮肤和皮下组织的损伤。利用磁场将电子污染扫离放射治疗区域，可以降低高能X射线对皮肤和皮下组织的剂量。这项工作旨在研究一种改进型磁偏转器产生的磁场，该磁偏转器使用钕铁硼磁铁。已使用Vizimag 3.0磁场建模软件模拟了该偏转器产生的磁场强度。改进后的偏转器磁场强度比其前身更加均匀，并且经过优化，便于安装在临床直线加速器上。还进行了所产生磁场强度的实验测量，以便进行比较。结果表明，在偏转器的中心区域，与Vizimag建模结果匹配度相对较好。在6兆伏X射线能量下，对于20×20平方厘米的射野，皮肤和皮下剂量最多可降低至原始值的34%。
