What is single photon emission computed tomography (SPECT)

A functional imaging procedure developed in the 1960s that uses radionuclides (radioactive substances injected into the body that specific cells and tissues absorb) to create perceptions of internal body structures that are then constructed and projected through computerized imaging techniques. SPECT can provide insights into the functioning of internal brain structures such as the basal ganglia and it constitutes a basic method of monitoring the loss of dopaminergic neurons of a person who has Parkinson’s disease, if this is desired. The primary value of this application is to research, although some neurologists use SPECT to help determine whether dopaminergic medications are improving dopamine presence and action in the brain.

In SPECT, the person receives an injection of the radionuclide and lies on a table that moves inside a large donut-shaped device. There is no discomfort beyond the placement of the IV for the initial injection, although some people feel claustrophobic while inside the device. Special detectors within this device collect the signals that the radionuclides emit and send the signals to the computer. Using complex mathematical formulas and physiological models, the computer creates multidimensional images of the body structures and representations of their functioning.

SPECT is less precise than radionuclide imaging technology such as positron emission tomography (PET), which uses a dual collection procedure that allows greatly refined images. However, PET requires sophisticated and expensive equipment and highly trained specialists to operate it, and its cost is about three times higher than the cost of SPECT. For most clinical applications in Parkinson’s disease, SPECT provides adequate information and is more readily available. There are no adverse effects of having SPECT.