Leide-Svegborn S
Medical Radiation Physics, Department of Clinical Sciences Malmö, Lund University, Malmö, Sweden.
Radiat Prot Dosimetry. 2010 Apr-May;139(1-3):208-13. doi: 10.1093/rpd/ncq026. Epub 2010 Feb 18.
The positron emission tomography (PET)/computed tomography (CT) camera is a combination of a PET camera and a CT. The image from the PET camera is based on the detection of radiation that is emitted from a radioactive tracer, which has been given to the patient as an intravenous injection. The radiation that is emitted from the radioactive tracer is more energetic than any other radiation used in medical diagnostic procedures and this requires special radiation protection routines. The CT image is based on the detection of radiation produced from an X-ray tube and transmitted through the patient. The radiation exposure of the personnel during the CT procedure is generally very low. Regarding radiation exposure of the patient, it is important to notice whether a CT scan has been performed prior to the PET/CT in order to avoid any unnecessary irradiation. The total effective dose to the patient from a PET/CT procedure is approximately 10 mSv. The major part comes from internal irradiation due to radiopharmaceuticals within the patients (e.g. (18)F-FDG: approximately 6-7 mSv), and a minor part is due to the CT scan (low-dose CT scan: approximately 2-4 mSv). If a full diagnostic CT investigation is performed, the effective dose may be considerably higher. If the patient is pregnant, a PET/CT procedure should be avoided or postponed, unless it is vital for the patient. An interruption in breastfeeding is not necessary after a PET/CT procedure of the nursing mother. Close contact between the patient and a small child should however be avoided for a couple of hours after the administration of the radiopharmaceutical. The radiation dose to the personnel arises mainly due to handling of the radiopharmaceuticals (syringe withdrawal, injection, waste handling, etc.) and from close contact to the patient. This radiation dose can be limited by using the inverse-square law, i.e. by using the fact that the absorbed dose decreases substantially with increasing distance between the radiation source and the personnel.
正电子发射断层扫描（PET）/计算机断层扫描（CT）相机是PET相机和CT的组合。PET相机的图像基于对放射性示踪剂发出的辐射的检测，该放射性示踪剂已通过静脉注射给予患者。放射性示踪剂发出的辐射比医学诊断程序中使用的任何其他辐射能量更高，这需要特殊的辐射防护程序。CT图像基于对X射线管产生并穿过患者的辐射的检测。CT检查过程中人员的辐射暴露通常非常低。关于患者的辐射暴露，重要的是要注意在进行PET/CT之前是否进行过CT扫描，以避免任何不必要的照射。PET/CT检查给患者带来的总有效剂量约为10毫希沃特。主要部分来自患者体内放射性药物的内照射（例如，（18）F-FDG：约6-7毫希沃特），一小部分来自CT扫描（低剂量CT扫描：约2-4毫希沃特）。如果进行全面的诊断性CT检查，有效剂量可能会高得多。如果患者怀孕，除非对患者至关重要，否则应避免或推迟PET/CT检查。哺乳期母亲进行PET/CT检查后无需中断母乳喂养。然而，在给予放射性药物后的几个小时内，应避免患者与小孩密切接触。人员的辐射剂量主要源于放射性药物的处理（注射器抽取、注射、废物处理等）以及与患者的密切接触。这种辐射剂量可以通过使用平方反比定律来限制，即利用吸收剂量随着辐射源与人员之间距离的增加而大幅降低这一事实。
