Single-photon emission computed tomography

Single-photon emission computed tomography (SPECT) reconstructs three-dimensional images of radiotracer distribution by detecting gamma rays emitted from the body at multiple angles.

Gamma camera: A detector that forms images by registering gamma rays emitted from radioactive tracers. Rotating gamma cameras collect the projections used to reconstruct SPECT slices.
Myocardial perfusion imaging: Imaging that assesses blood flow to the heart muscle, often at rest and during stress. Cardiac SPECT detects regional differences in radiotracer uptake that indicate impaired perfusion.
Positron emission tomography: A nuclear imaging technique that reconstructs tracer distribution from pairs of annihilation photons. PET detects coincident photon pairs, while SPECT detects individual gamma photons.
Radiopharmaceutical: A medicinal compound containing a radioactive isotope for diagnosis or therapy. SPECT radiopharmaceuticals deliver the gamma-emitting radionuclide to tissues of interest.
Collimator: A device that filters radiation by direction, commonly using an array of narrow channels. Its channels select the directions of gamma rays reaching the camera, trading sensitivity for spatial resolution.
Bone scintigraphy: Nuclear medicine imaging that maps radiotracer uptake in bone. SPECT can add three-dimensional localization to bone scans in complex or overlapping regions.
Computed tomography: An imaging method that reconstructs internal anatomy from measurements of transmitted X-rays. CT primarily maps tissue attenuation; SPECT maps the distribution of an injected radiotracer.
Gamma ray: A high-energy photon emitted by an atomic nucleus or another energetic process. Gamma rays escaping the body are the signals detected in SPECT.
Radionuclide: An unstable atomic nucleus that decays and emits radiation. SPECT tracers contain radionuclides whose gamma emissions the camera detects.
Brain perfusion SPECT: SPECT imaging that estimates regional cerebral blood flow using a radiotracer. It maps functional blood-flow patterns in neurological and psychiatric investigations.

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