Abstract

CHOW ROBILOTTA, Cecil. Emission Tomography: SPECT and PET. Comp. y Sist. [online]. 2004, vol.7, n.3, pp.167-174. ISSN 1405-5546.

Emission tomography is a medical image modality that utilizes molecules labelled with radionuclides, the radiopharmaceuticals, to obtain functional information about specific tissues or systems. In SPECT, Single Photon Emission Computerized Tomography, the radionuclide decays by emitting one or more photons, while in PET, Positron Emission Tomography, the radionuclide emits a positron, in order to reach a lower energy level. Although the forms of energy emitted are different, the images are reconstructed from the information acquired by external detection of the emitted photons (SPECT) and the pair of annihilation photons (PET) in coincidence. Due to the specificity and characteristics of these images, their information can be quantified, so that functional or metabolic parameters can be obtained for diagnostic or therapeutic purposes. However, in order to achieve reliable results, factors related to the instrumentation and patient conditions, as well as to the interactions between radiations and tissues and the reconstruction methods have to be considered carefully. In this lecture, after the introduction of the fundamentals of nuclear medicine imaging, the basis of emission tomography acquisition and reconstruction will be presented. Some correction methods will be introduced in order to exemplify the current quantifications adopted in the clinical routine of molecular imaging.

Keywords : Emission tomography; functional imaging; iterative reconstruction; nuclear medicine; PET; quantification; SPECT.

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