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. Your child may eat and drink as usual.
  • Your child should wear comfortable clothing during the examination.
  • Remove all metal objects (jewellery, keys, coins, pens, etc.) before the examination. These can cause defects in the scan.
  • Inform your child that a needle will be injected into his/her arm or hand. Reassure your child that s/he will feel only a small prick from the needle.
  • Let your child know that the technologist will be in the examination area at all times if s/he needs anything.

During a SPECT Exam

  • A technician will ask you about your child’s medical history (e.g. head injury, seizures, stroke).
  • Your child will lie on his/her back while the technician injects and a small amount of radioactive substance into a vein in his/her arm or hand. This radioactive agent will localize in an area of the brain and will be imaged with a camera.
    • 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.
  • Your child will remain lying down for another 10 to 20 minutes.
  • The technician will move a large camera near your child’s head.
    • It will take several pictures that show how well blood flows through various areas of your child’s brain.
    • The camera will remain close to your child’s head throughout the exam. It rotates once around his/her head and lightly brushes your child’s shoulders. It will not touch any other part of the 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.
  • Your child will be instructed to remain still and breath normally. Any movement will blur the images. Your child may have to repeat the scan if there is movement of the head.
    • If your child is too young to keep his/her head still, s/he may require sedation.
  • Your child 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, the technologist will return to assist your child off the table. You child may go home and resume normal activities.
  • A radiologist or physician will interpret the images and send a report to your child’s 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.
  • Inform your doctor if your child is or may be pregnant, before proceeding with a nuclear medicine scan.

Click here to learn about other types of diagnostic tests.

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