Saeed M K, Moustafa O, Yasin O A, Tuniz C, Habbani F I
Radiation and Isotope Center, Khartoum, PO Box 846, Sudan.
Radiat Prot Dosimetry. 2009 Feb;133(3):130-5. doi: 10.1093/rpd/ncp029. Epub 2009 Mar 15.
This study of doses to patients from emitted photoneutrons in a medical linear accelerator (Varian 2100C) was carried out. Dose calculation was performed using Monte Carlo Geant4 code. The model was used to calculate the neutron fluence, as a function of the neutron energy inside the treatment room to estimate the effective dose to patients. The ambient dose equivalent versus field size for patients is reported in this study. The ambient dose equivalent using 1 x 1 cm(2) field size, at isocentre and X-ray modes of 20, 18, 15 and 10 MV, was found to be 1.85, 1.79, 0.61 and 0.06 mSv Gy(-1), respectively. The mean energies of emitted photoneutrons were 0.48, 0.44, 0.40 and 0.16 MeV at X-ray modes of 20, 18, 15 and 10 MV, respectively. The results of ambient dose equivalent from emitted photoneutrons cannot be ignored and can represent a risk for healthy tissues. This study emphasised that Geant4 Monte Carlo code is an appropriate choice for studying photoneutron production and transport.
本研究对医用直线加速器（瓦里安2100C）发射的光中子对患者的剂量进行了研究。使用蒙特卡罗Geant4代码进行剂量计算。该模型用于计算中子注量，作为治疗室内中子能量的函数，以估计患者的有效剂量。本研究报告了患者的周围剂量当量与射野大小的关系。发现在等中心以及20、18、15和10 MV的X射线模式下，使用1×1 cm²射野大小的周围剂量当量分别为1.85、1.79、0.61和0.06 mSv Gy⁻¹。在20、18、15和10 MV的X射线模式下，发射的光中子的平均能量分别为0.48、0.44、0.40和0.16 MeV。发射的光中子产生的周围剂量当量结果不容忽视，可能对健康组织构成风险。本研究强调，Geant4蒙特卡罗代码是研究光中子产生和传输的合适选择。
