Madsen Mark T, Anderson Jon A, Halama James R, Kleck Jeff, Simpkin Douglas J, Votaw John R, Wendt Richard E, Williams Lawrence E, Yester Michael V
Radiology, University of Iowa, USA.
Med Phys. 2006 Jan;33(1):4-15. doi: 10.1118/1.2135911.
The shielding of positron emission tomography (PET) and PET/CT (computed tomography) facilities presents special challenges. The 0.511 MeV annihilation photons associated with positron decay are much higher energy than other diagnostic radiations. As a result, barrier shielding may be required in floors and ceilings as well as adjacent walls. Since the patient becomes the radioactive source after the radiopharmaceutical has been administered, one has to consider the entire time that the subject remains in the clinic. In this report we present methods for estimating the shielding requirements for PET and PET/CT facilities. Information about the physical properties of the most commonly used clinical PET radionuclides is summarized, although the report primarily refers to fluorine-18. Typical PET imaging protocols are reviewed and exposure rates from patients are estimated including self-attenuation by body tissues and physical decay of the radionuclide. Examples of barrier calculations are presented for controlled and noncontrolled areas. Shielding for adjacent rooms with scintillation cameras is also discussed. Tables and graphs of estimated transmission factors for lead, steel, and concrete at 0.511 MeV are also included. Meeting the regulatory limits for uncontrolled areas can be an expensive proposition. Careful planning with the equipment vendor, facility architect, and a qualified medical physicist is necessary to produce a cost effective design while maintaining radiation safety standards.
正电子发射断层扫描（PET）和PET/CT（计算机断层扫描）设备的屏蔽存在特殊挑战。与正电子衰变相关的0.511兆电子伏湮灭光子的能量比其他诊断辐射高得多。因此，地板、天花板以及相邻墙壁可能都需要进行屏障屏蔽。由于在注射放射性药物后患者会成为放射源，所以必须考虑患者在诊所停留的整个时间段。在本报告中，我们介绍了估算PET和PET/CT设备屏蔽要求的方法。总结了最常用的临床PET放射性核素的物理特性信息，不过本报告主要涉及氟-18。回顾了典型的PET成像方案，并估算了患者的照射率，包括身体组织的自吸收和放射性核素的物理衰变。给出了控制区和非控制区的屏障计算示例。还讨论了与闪烁相机相邻房间的屏蔽问题。同时还包括了0.511兆电子伏下铅、钢和混凝土的估计透射系数表和图表。满足非控制区的监管限值可能成本高昂。与设备供应商、设施建筑师和合格的医学物理学家仔细规划，对于在维持辐射安全标准的同时实现具有成本效益的设计是必要的。
