SPECT/CT Scan Definition

Single photon emission computed tomography/computed tomography (SPECT/CT) combines two different diagnostic scans into one for a more complete view of the body region being studied. The SPECT scan uses nuclear medicine to give good images of metabolic abnormalities, whereas the CT scan may be able to help narrow down specifically where the problem is occurring, such as in the bone or nearby tissue.

How a SPECT/CT Scan Works

A SPECT/CT scan typically involves 3 main components:

1. A radioactive tracer is injected into the body’s bloodstream. This tracer can be seen by a gamma scanner, which shows metabolic functions of tissues and organs, such as blood flow and potential abnormalities in the tissues.
2. A CT scan is taken with an x-ray scanner rotating around the body region being studied.
3. A SPECT scan is taken with a gamma scanner rotating around the body region being studied, which takes much longer than the CT scan.

Since the SPECT and CT scans both form cross-section images of the same areas, the computer is able to combine these images. The resulting cross-section images show the x-ray images of the bones overlaid with the nuclear imaging.

When a SPECT/CT Scan Is Considered

A SPECT/CT scan may be particularly useful when trying to get a look at a metabolic abnormality, as well as its location in relation to the bone. For example, SPECT/CT may show that an abnormality suspected of causing back pain is actually located in the facet joint rather than the vertebral body or another part of the spine. Another example would be to see how much of a cancerous tumor has gone into the bone.

While SPECT/CT is considered relatively safe, this combined scan tends to use more radiation than other scans. Women who are pregnant are not recommended to have a SPECT/CT scan due to the risks associated with radiation exposure.