Single-Photon Emission Computed Tomography ∞ Area

Single-Photon Emission Computed Tomography

Meaning

Single-Photon Emission Computed Tomography (SPECT) is a nuclear medicine imaging technique providing three-dimensional functional organ information. It detects gamma rays from an administered radiotracer, localizing based on physiological activity. This non-invasive method visualizes blood flow, metabolism, and receptor distribution, offering insights into cellular function beyond anatomy.

Context

SPECT operates within molecular imaging, complementing anatomical modalities like CT or MRI with functional data. It evaluates systems where blood flow or metabolic activity is critical, including heart, brain, and bones, and identifies neuroendocrine tumors. The technique uses physiological radiopharmaceutical uptake to reveal altered function, often preceding structural changes.

Significance

SPECT impacts clinical decision-making, enabling early detection and precise localization of functional abnormalities. In cardiology, it assesses myocardial perfusion, guiding revascularization. In neurology, it aids diagnosing epilepsy or Parkinson’s by mapping cerebral blood flow or dopamine transporter availability. This insight is crucial for tailoring treatment and monitoring progression.

Mechanism

The mechanism involves intravenous administration of a radiopharmaceutical, labeled with a gamma-emitting radioisotope. This tracer distributes by targeted physiological process. As the radioisotope decays, it emits single photons detected by rotating gamma cameras. A computer reconstructs these signals into a three-dimensional image, representing the tracer’s spatial distribution.

Application

SPECT is widely applied clinically. It localizes hyperfunctioning parathyroid glands and identifies neuroendocrine tumors. Myocardial perfusion SPECT (MPS) detects coronary artery disease. Neurologists use SPECT to differentiate dementias or localize seizure foci. It aids bone imaging for fractures, infections, metastatic disease, and assesses thyroid function.

Metric

SPECT scan output presents as cross-sectional images or a reconstructed three-dimensional volume, color-coded for tracer uptake intensity. Quantitative metrics, like myocardial perfusion scores or standardized uptake values (SUV), can be derived. These metrics allow clinicians to objectively assess functional impairment or metabolic activity, assisting diagnosis and treatment response monitoring.

Risk

Primary risks include ionizing radiation exposure from the radiopharmaceutical; doses are low and clinically justified. Allergic reactions to the radiotracer are rare. SPECT is contraindicated for pregnant individuals due to potential fetal radiation exposure. Renal impairment may require dose adjustments. Careful patient selection and protocol adherence minimize risks.

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HRTioJuly 19, 2025