Note that all nuclides with Z >83 (bismuth) are radioactive and that, in general, the further the radionuclide is from the line of stability, the more unstable it is and the shorter the half-life it has. The stable nuclides form the so-called line of stability in which the neutron-to-proton ratio is approximately 1 for low Z nuclides and increases to approximately 1.5 for high Z nuclides. A plot of the nuclides where the number of protons (ie, atomic number or Z ) and neutrons of each nuclide is shown on the x – and y -axes, respectively.SPECT/CT, PET/CT, and PET/MRI are powerful hybrid imaging tools. Such hybrid imaging allowsįor increased diagnostic accuracy of nuclear imaging. This corresponding anatomic information can be provided by combining nuclear imaging data with anatomic imaging data, such as CT. Radiopharmaceuticals localize to tissues or compartments on the basis of various mechanisms (see Section “Mechanisms of Radiopharmaceutical Localization” later), and therefore nuclear imaging does not illustrate the full spectrum of anatomy within a region of interest. The resolutions of planar gamma camera imaging, single-photon emission computed tomography (SPECT) and positron emission tomography (PET) are lower than that of X-ray computed tomography (CT) and magnetic resonance imaging (MRI) by an order of magnitude or more ( Figure 8.2). ![]() ![]() ![]() Gamma rays and X-rays produced during nuclear transformation can be detected for image creation as well as for quantification. Unlike most other imaging modalities in medicine, nuclear medicine imaging generally focuses on depicting normal physiology and disturbances of function.
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