By tracking blood flow levels through arteries and veins, in tissues and organs, studies using nuclear medicine provide detailed images of specific areas of physiological functioning. Different types of imaging used in nuclear medicine studies can detect and diagnose numerous diseases, infections, neurological disorders and brain damage, ranging from cancer and heart conditions, to epilepsy and Attention Deficit Disorder (ADD), and even strokes and drug abuse.
SPECT/SPET – Nuclear Medicine
Single Photon Emission Computed Tomography or SPECT/SPET is an example of a nuclear medicine study that can be used to track cerebral blood flow and detect blood flow changes and brain metabolic activity.
SPECT studies require a small amount of radioactive label/tracer or dye, otherwise known as a radiopharmaceutical, to be intravenously injected into the patient’s body. This radiopharmaceutical contains a gamma-emitting radioisotope useful for its unstable radioactive properties and its rapid decay.
The radioisotopes typically used in SPECT to label tracers are iodine-123, technetium-99m, xenon-133, thallium-201, and fluorine-18. All are considered safe, and do not remain in the body; the type of results and test required will determine which tracer is chosen.
How do SPECT Studies Work?
SPECT studies use tracers that remain in the blood stream instead of being absorbed by surrounding tissues, thereby limiting the information in the images provided to only areas in the body where blood flow is possible.
In the case of brain studies, for example, as this radioactive liquid travels around the cortex, it highlights cerebral functioning by emphasising active brain cells showing heavy blood flow and less active cells with light blood flows.
Generally, physicians note atypically over-active areas, under-active areas, and asymmetrical activity versus symmetrical activity.
How Does Nuclear Medicine Provide Images?
As the radioactive pharmaceutical passes through the system, it breaks down and emits short wavelength electromagnetic radiation in the form of beams of light known as gamma rays. These light sources are traced, absorbed, and recorded as events or counts by the crystal plates of a gamma camera or scanner. The greater the light source, the more active the area.
How are 3D images created?
The gamma camera records multiple 2D cross-sectional images/projections of 3D blood flow and cell activity. These images are then tomographically reconstructed into 3D images of the brain or other parts of the body which can be reformatted as required. The reconstruction provides true 3D information albeit of a lower resolution.
SPECT Scanning Studies offer the following unique qualities:
- SPECT studies provide functional information that is often unattainable using other imaging procedures.
- SPECT scanning studies are less expensive, and may produce more accurate information than exploratory surgery.
- These studies need no pre-procedure preparation.
- SPECT reconstruction supplies useful information for pre-surgical evaluation.
- Studies with SPECT involve low radiation exposure, less than you receive during a chest X-ray or CT scan.
Note: Women who are pregnant or breast feeding should not undergo a SPECT scan.
Radiological Society of North America, Inc. (RSNA). Radiology. Accessed November 7, 2011.
IAEA Human Health Campus. SPECT. Accessed November 7, 2011.
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