Compounding of PET radiopharmaceuticals

USP Chapter <823> describes at length the guidelines for compounding of PET radiopharmaceuticals. For the sake of brevity, only a brief outline will be presented here. 

In the above section, requirements for compounding of PET radiopharmaceuticals have been presented. In this section, the methods of quality control tests for these products are briefly described below. Since PET radiopharmaceuticals are short-lived, some lengthy tests cannot be performed prior to release for human use and so they are performed within a short time after the release. 

Nuclear medicine is used chiefly in medical diagnosis. A radiopharmaceutical—a relatively harmless compound with a low dose of radiation— is swallowed or injected into the patient and tracked through the bloodstream by instruments such as a PET (positron emission tomography) camera. The nuclear physician can use the results to create a... 

The second feature that distinguishes F from the ultrashort-lived isotopes is that its stable counterpart F is not commonly found in endogenous compounds. In most cases, the new F-labeled radiopharmaceuticals are analogues of well-documented compounds. As the analogues are new chemical entities, a large documentation on toxicology and other aspects influencing their safe use in human has been a prerequisite before human PET studies could be initiated. 

Since emission tomography requires some type of internal radioactive sources, a large number of radionuclides have been developed and produced specifically for these applications. Gamma emitters are used for SPECT, while positron emitters are used for PET. The chemical form of a radionuclide is tailored specifically for a given target (tissue, bone, or organ). Compounds labeled with radionuclides for administration to patients are known as radiopharmaceuticals. 

Radiopharmaceuticals with very high specific activity (5-15 Ci mmol ) are used in PET studies so as to retain the pharmaceutical, biological, and biochemical properties of the compound being studied. This section reviews the common radiosynthetic methods, the selection of a suitable radio-tracer, and limitations in the preparation of radiopharmaceuticals. 

Mental disorders are diagnosed by SPECT, gamma-camera or PET using various radiopharmaceuticals, e.g. after the injection of Tc-HMPAO (Hexa Methyl Propylene Amine Oxide) or inhalation of Xe. Injecting 1000 MBq Tc-complex into the blood stream, about 5 % of this compound moves to the brain, passes the membrane of the blood vessels and enters into the brain tissue, where it decomposes and decays with its 6.0 h half-... 

---