Neurologic PET CT Prep

Find out when you book

Medically reviewed by Dr. Alex Tamm, BMSc, MD (STIR), FRCPC

PET CT for the Brain

PET CT imaging of the brain can help evaluate intracranial changes in cell metabolism linked with neurodegenerative conditions and dementias. Your practitioner might refer to this exam as an FDG PET CT scan. FDG stands for Fluorodeoxyglucose and is a popular radiotracer for neurological applications.

What does a PET CT scan of the brain show?

Our radiologists can use the information gathered from PET CT imaging of the brain to help your practitioner evaluate, differentiate and treat various conditions, including but not limited to:

  • Alzheimer’s disease
  • Parkinson’s disease
  • Frontotemporal lobar degeneration
  • Intractable epilepsy
  • Tumours
  • And more

Which radiotracer is used in neurologic PET CT imaging?

All PET CT applications use a positron-emitting radiotracer, but different tracers target different proteins in the body. For neurological PET CT imaging, MIC injects the following radiotracers intravenously:

  • FDG (fluorodeoxyglucose)

What happens during a PET CT scan of the brain?

During a PET scan of the brain, a technologist will insert an intravenous (IV) catheter into your arm. Next, we inject a tiny amount of radiotracer (most commonly sugar/glucose) into your veins through the IV line.

The tracer needs time to travel through your body and reach the brain. Usually, this process takes about 60 minutes. Once the tracer has reached your brain, we will position you on the exam table and capture images for our nuclear medicine/computed tomography radiologist to review.

Do I have to fast before my neurological PET CT?

In some cases, patients must refrain from eating food before their neurologic PET CT. Exams that use FDG as a tracer require patients to refrain from eating (typically 6 hours). Our central booking team will review specific exam preparations when booking the appointment.

When will I get the results from my PET CT scan of the brain?

After the PET CT scan of the brain, a dual-trained and certified MIC nuclear medicine physician and radiologist will review the images and send a detailed report to your referring practitioner, usually within one or two business days.

Neurological PET CT FAQs

FDG uptake in a PET-CT scan refers to the accumulation of FDG (Fluorodeoxyglucose) radiotracer within tissues or organs in the brain, spinal cord, or nerves. FDG is particularly helpful for visualizing metabolic activity in an area of interest.

Some organs, like the brain, normally use large amounts of glucose for energy and take up proportionately larger amounts of FDG. Therefore, many neurological disorders can cause reduced FDG uptake in specific affected brain regions. Specific patterns of lower than normal FDG uptake may indicate a degenerative process or dysfunction.

Higher than normal FDG uptake in a neurological PET CT scan may be indicative of an inflammatory process or abnormality. However, there is a misconception among patients that any level of uptake is abnormal – which is not always the case and can lead to unnecessary anxiety and concern.
No. Patients must avoid intense or strenuous exercise such as jogging, strength training, aerobics etc. before their appointment. Excessive muscle activity can interfere with the interpretation of your images.
Not for exams that use FDG as a tracer. Patients must avoid chewing gum before their appointment as it contains sugar and other additives that may impact imaging results.
Yes. We instruct patients to follow a high protein/low carb diet before their appointment. Following the proper diet helps our team capture the best possible images. We encourage patients to limit the amount of bread, pasta, potatoes, cereals, rice, desserts, candy and sugar eaten before their appointment.
No. We instruct patients to avoid any medications that contain sugar, such as cough syrup or cough drops, before their appointment. Many cold medicines can also contain stimulants like caffeine that can affect brain metabolism.
Patients can drink as much plain water as they would like before their appointment. However, for exams using FDG as a tracer, they cannot drink any flavoured beverages, such as Gatorade, that contain sugar.
No. Patients must not use medical or recreational cannabis for 72 hours before their exam.

It is also important that patients do not take opiates and other derivatives for 6 hours before their exam. Opiates include but are not limited to morphine, codeine, etc.

Lastly, patients must not take valium or benzodiazepines for 6 hours before their exam. Benzodiazepines are often prescribed to help treat conditions such as anxiety, insomnia, and seizures. Our central booking team will review all preparation requirements when scheduling the appointment.
Applied Radiology. (2009). Cardiac and neurological PET-CT applications. https://appliedradiology.com/articles/cardiac-and-neurological-pet-ct-applications
Lovblad, K., Bouchez, L., Altrichter, S., Ratib, O., Zaidi, H., Vargas, M. (2019). PET-CT in neuroradiology. https://journals.sagepub.com/doi/full/10.1177/2514183X19868147
Murrell, D. (2018). Brain PET Scan. https://www.healthline.com/health/brain-pet-scan
Piccini, P., Tai, Y. (2004). Applications of positron emission tomography (PET) in neurology. https://jnnp.bmj.com/content/75/5/669