Radionuclides SPECT

PET and SPECT are both functional imaging methods that use externally administered radionuclide-labeled substances to image in vivo physiological processes in 3-D space 944... 

TABLE 58-2 Typical radionuclides employed in PET/SPECT and physical properties... 

Indications for radionuclide imaging in these patients are detailed in current ACC/AHA guidelines [68] and ACCF/ASNC appropriateness criteria for SPECT myocardial perfusion imaging [69]. While a detailed discussion of these indications is beyond the purpose of this text, for patients with advanced... 

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. 

PET radiopharmaceuticals offer enhanced spatial resolution and quantification capabilities compared with SPECT agents. To probe Pgp transport activity, PET-based radiopharmaceuticals have been actively investigated on three fronts (1) use of SPECT scaffolds capable of accommodating PET radionuclides, (2) bioinorganic radiochemistry, and (3) conventional PET organic radiochemistry. 

Nuclear imaging can be considered as a pure molecular imaging technique, since it can directly detect the molecules in which the radionuclides have been embedded. These compounds are called radiopharmaceuticals or radiotracers . Typical radionuclides for SPECT imaging are Tc, In, M, and Ga. Be-... 

Due to their high sensitivity, nuclear imaging techniques are well-suited to visualize targets present at low concentrations. PET and SPECT, with their picomo-lar sensitivity, allow for the imaging of most known targets using ligands that carry only one label each. As the radionuclide label is relatively small, the probes may even permeate into cells. However, the spatial resolution of nuclear techniques lies in the order of a few to tens of miUi-... 

Radiopharmaceuticals labeled with " Tc are commercially available and are employed in more than 80% of all nuclear medicine investigations. Among the radionuclides, technetium-99m is most attractive to the nuclear medicine physician because of its optimal gamma energy for SPECT, its availability, its relatively low cost, and its easy-to-la-bel kit preparations for in-house use. Another advantage is the low radiation burden to patients, due primarily to its short half-life. The decay within hours also facilitates the handling of waste. 

---