Single Photon Emission Computed Tomography Guide

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When a doctor wants to analyze a patient’s internal organs, they send them for a single-photon emission computed tomography scan. This nuclear imaging test uses a special camera and a radioactive substance to create pictures of a person’s organs. This scan creates 3-D images that show how a person’s organs are working.

What is a SPECT Scan Used For?

This scan can be used to monitor or diagnose a variety of diseases and conditions, including:

  • Heart problems, such as heart or artery blockages, heart attack, and chest pain
  • Brain disorders, such as stroke, seizure, and Alzheimer’s disease
  • Cancer, including cancers that have spread and primary tumors

How to Prepare for a SPECT Scan?

What a patient has to do to prepare depends on their particular situation. The patient’s doctor will discuss all preparations with them prior to having this scan done.

What to Expect and How this Scan is Done

Single-photon emission computed tomography begins with the patient either inhaling the radioactive dye (referred to as the tracer) or having it intravenously introduced into the body through a vein in the arm. The tracer will be processed by the body, with the tissues in the body that are more active, absorbing more of the tracer. For example, cancer cells or the area of the brain causing a seizure will often absorb more of the tracer. This allows the doctor to determine the specific problem area, or problem areas. The patient will lie on a table in the scanning room and the technologist will help to get them properly positioned. The SPECT machine will rotate around the patient as they lie there taking 3-D images of their internal organs. How long the scan takes ultimately depends on why the patient is getting the scan, but the average time this scan takes is about one to two hours.

The tracer will be excreted by the urine. Any leftover tracer will be broken down by the body over the next 48 hours.

Possible Risks of a SPECT Scan

For most patients, this scan is perfectly safe. Those who receive an infusion or injection of the radioactive tracer are at risk to experience:

  • Pain, swelling, or bleeding at the site where the needle was inserted into the arm
  • In rare cases, a patient may have an allergic reaction due to the radioactive tracer used

During this scan patients are exposed to radiation, but the level is similar to what they will experience out in the environment naturally over the course of a full year. Those who are concerned about the radiation exposure should talk to their doctor prior to have this scan done to address their concerns.


Mayo Clinic. (2009). SPECT Scan. Retrieved on July 23, 2010 from the Mayo Clinic:

Mayfield Clinic. (2010). SPECT Scan. Retrieved on July 23, 2010 from the Mayfield Clinic: