Single Photon Emission Computed Tomography (SPECT)

August 8, 2011

Single Photon Emission Computed Tomography is a functional imaging technique that creates three-dimensional images of the brain on computer. This allows physicians to visualize blood flow through different areas of the brain.

Individuals with epilepsy often have changes in blood flow to specific areas of the brain when a seizure begins. SPECT measures blood flow between and during seizures. Physicians compare these scans to identify the blood flow changes in specific areas of the brain to identify where seizures originate.

Measuring the relative cerebral blood flow demonstrates how well the various regions of the brain are functioning . This information helps physicians to more accurately diagnose the type of seizure, locate the site where a seizure originates and evaluate a potential candidate for surgery.

The radiation exposure from a brain scan is small. It is in the range of one to three times your annual exposure to natural background radiation.

Before a SPECT Exam

  • No special diet or medication is required.
  • Dress in comfortable clothing.
  • Remove all metal objects (jewellery, keys, coins, pens, etc.) to prevent defects in the scan.

During a SPECT Exam

  • A technician will ask you about your past medical history (e.g. head injury, seizures, stroke).
  • You will lie on your back while the technician injects and a small amount of radioactive substance into a vein in your arm or hand.
    • This radioactive agent will localize in an area of the brain for the camera to capture.
    • Adverse reactions to this substance are very rare. Even then, it is only a mild skin reaction such as a rash.
  • You will remain lying down for another 10 to 20 minutes.
  • The technician will move a large camera near your head.
    • It will take several pictures that show how well blood flows through various areas of your brain.
    • The camera will remain close to your head throughout the exam. It rotates once around your head and lightly brushes your shoulders. It will not touch any other part of your body.
  • The only sounds you will hear are the slight noise of the camera rotation and the cooling fans in the equipment.
    • There are no loud noises during the examination.
  • Remain still and breath normally.
    • Any movement will blur the images. You may have to repeat the scan if you move your head.
  • You will be able to communicate with the technologist throughout the procedure.
  • Preparation for the examination takes 30 minutes. The imaging takes another 30 minutes.

After a SPECT Exam

  • When scanning is complete, you may resume your normal activities.
  • A radiologist or physician will interpret the images and send a report to your doctor.


  • Nuclear Medicine Technologists (NMTs)
    • work under the supervision of physicians to perform the SPECT exam
    • prepare, measure and give radioactive tracers to patients orally or by injection
  • Doctors
    • interpret results


A SPECT exam is covered by the Ontario Health Insurance Plan (OHIP).

Important Considerations

  • Pregnant women should not undergo a SPECT scan because of the radioactive isotopes used. Be sure to inform your doctor if you are or suspect you may be pregnant before proceeding with a nuclear medicine scan.

Click here to learn about other types of diagnostic tests.

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