Mesbahi Asghar, Keshtkar Ahmad, Mohammadi Ehsan, Mohammadzadeh Mohammad
Medical Physics Department, Medical School, Tabriz University of Medical Sciences, Tabriz, Iran.
Appl Radiat Isot. 2010 Jan;68(1):84-9. doi: 10.1016/j.apradiso.2009.08.008. Epub 2009 Aug 25.
Photoneutrons produced during radiation therapy with high energy photons is the main source of unwanted out-of-field received doses of patients. To analyze the neutron dose equivalent (NDE) for wedged beams and its variation with field size, Monte Carlo (MC) modeling of an 18MV photon beam was performed using MCNPX MC code. The results revealed that the NDE is on average 6.5 times higher for wedged beams. For open beams, the NDE decreased with increasing field size especially for field sizes >20x20cm(2). While, for wedged beams, the NDE increased with field size. It was suggested that the increase of NDE for wedged beams should be taken into account in radiation-induced secondary cancer risk estimations and radiation protection calculations.
高能光子放射治疗过程中产生的光中子是患者额外接受的野外剂量的主要来源。为了分析楔形射束的中子剂量当量（NDE）及其随射野大小的变化，使用MCNPX蒙特卡罗（MC）代码对18MV光子束进行了蒙特卡罗（MC）建模。结果显示，楔形射束的NDE平均高出6.5倍。对于开放射束，NDE随射野大小增加而降低，特别是对于射野大小>20x20cm²的情况。而对于楔形射束，NDE随射野大小增加。有人建议，在辐射诱发的继发性癌症风险评估和辐射防护计算中应考虑楔形射束NDE的增加。
