Unidade de Protecção e Segurança Radiológica, IST/CTN, Instituto Superior Técnico, Universidade Técnica de Lisboa, Estrada Nacional 10 km 139,7, 2686-953 Sacavém, Portugal.
Phys Med Biol. 2013 Aug 21;58(16):5433-48. doi: 10.1088/0031-9155/58/16/5433. Epub 2013 Jul 23.
This work aims to contribute to the study of the radiation dose distribution delivered to the hands of medical staff members during a general computed tomographic (CT) fluoroscopic guided procedure. In this study, both Monte Carlo simulations and measurements were performed. For free-in-air and computed tomography dose index (CTDI) body phantom measurements, a standard pencil ionization chamber (IC) 100 mm long was used. The CT scanner model was implemented using MCNPX (Monte Carlo N-Particle eXtended) and was successfully validated by comparing the simulated results with measurements. Subsequently, CT images of a hand, together with an anthropomorphic phantom, were voxelized and used with the MCNPX code for dose calculations. The hand dose distribution study was performed both by using thermo-luminescent detector measurements and Monte Carlo simulations. The validated simulation tool provides a new perspective for detailed investigations of CT-irradiation scenarios. Simulations show that there is a strong dose gradient, namely the even zones of the hand that are in precise vicinity to the x-ray beam only receive about 4% of the maximum dose delivered to adjacent areas which are directly exposed to the primary x-ray beam. Finally, the scatter contribution of the patient was also studied through MC simulations. The results show that for directly exposed parts of the hand surface, the dose is reduced by the body of the patient (due to the shielding), whereas the dose is increased by scattered radiation from the patient for parts of the skin that receive scattered radiation only.
这项工作旨在研究在一般计算机断层扫描 (CT) 透视引导程序中，医务人员手部接受的辐射剂量分布。在这项研究中，进行了蒙特卡罗模拟和测量。对于自由空气和计算机断层扫描剂量指数 (CTDI) 体模测量，使用了标准的铅笔电离室 (IC) 长 100 毫米。使用 MCNPX（Monte Carlo N-Particle eXtended）实现了 CT 扫描仪模型，并通过将模拟结果与测量结果进行比较成功地验证了该模型。随后，对手部和拟人化体模的 CT 图像进行了体素化，并使用 MCNPX 代码进行剂量计算。通过使用热释光探测器测量和蒙特卡罗模拟来进行手部剂量分布研究。经过验证的模拟工具为详细研究 CT 照射场景提供了新的视角。模拟结果表明存在很强的剂量梯度，即仅与 X 射线束精确相邻的手部均匀区域仅接收输送到相邻区域的最大剂量的 4%，而相邻区域直接暴露于初级 X 射线束。最后，还通过 MC 模拟研究了患者散射的贡献。结果表明，对于手部表面直接暴露的部分，由于屏蔽，患者身体会降低剂量，而对于仅接收散射辐射的皮肤部分，散射辐射会增加剂量。
