Specialist diagnostic testing
SPECT Scan
A SPECT scan can show patterns of blood flow in the brain. In selected epilepsy assessments, it helps the specialist team investigate where seizures may begin.
About this information
This webpage is subject to continuous review by Epilepsy Ontario to help keep the information current. This material is for informational purposes only and should not be used for self-diagnosis or as a substitute for professional medical advice, diagnosis, or treatment. Consult your healthcare provider about your own health and care.
What is SPECT?
SPECT stands for single-photon emission computed tomography. A small amount of a radioactive tracer is injected into a vein. A special camera detects signals from the tracer to produce images.
In epilepsy assessment, the tracer provides information about blood flow around the time it is injected. This answers a different question from a structural MRI or an EEG recording.
Comparing two points in time
Ictal SPECT
Injection during a seizure
The tracer is injected as promptly as possible during a seizure under specialist supervision. The images are collected afterward.
Interictal SPECT
Injection between seizures
A separate study provides a comparison of blood flow between seizures. The team explains how the studies will be arranged.
The team may compare the studies and combine the information with MRI images. One method is called SISCOM.
Not everyone with epilepsy needs SPECT. It is generally used for specific specialist questions, often during an assessment for epilepsy surgery. Findings must be considered alongside other test results.
Before your appointment
- Follow the nuclear medicine and epilepsy teams’ instructions.
- Bring a list of medications and supplements.
- Tell the team if you are pregnant, might be pregnant, or are breastfeeding.
- Report previous reactions to injected substances and relevant health conditions.
- Ask about food, drink, appointment length, and whether admission is required.
Do not try to trigger a seizure yourself. Do not skip medication, lose sleep, or change your routine unless the specialist team explicitly directs and supervises the plan.
During the study
A small intravenous line is used for the tracer injection. For an ictal study, the timing is coordinated by the epilepsy monitoring team.
For imaging, you lie on a table while the camera collects signals around your head. Remaining still helps the team obtain clear images.
The injection and image collection may happen at different times. Your team will explain the schedule.
Radiation and aftercare
SPECT involves exposure to ionizing radiation from the tracer. The team considers the expected benefit and individual circumstances before recommending the study.
Follow the instructions provided about fluids, close contact with others, and breastfeeding. Advice depends on the tracer and examination; do not assume the same instructions apply to CT contrast and nuclear medicine tracers.
Understanding the results
Specialists interpret the images together with your EEG, MRI, seizure history, and other assessments. SPECT alone does not establish the full diagnosis or determine whether surgery should proceed.
Questions to ask
- What question is this study intended to answer?
- Will I need both ictal and interictal studies?
- Will testing take place during an epilepsy monitoring admission?
- What preparation and aftercare apply to my tracer?
- Who will explain the findings and next steps?
