Brain PET-CT Scan: Procedure, Uses, and What to Expect

A brain PET-CT scan is an advanced nuclear medicine imaging test that combines Positron Emission Tomography (PET) and Computed Tomography (CT) to give information about the function as well as the structure of the brain. While imaging tests primarily provide information about the structure of the brain, a PET-CT can help physicians determine which parts of the brain are consuming glucose or another particular type of tracer. In Molecular Diagnostics and Therapy, we use powerful imaging technology (PET-CT scan) to assess certain neurological/brain conditions. 

What Is a Brain PET-CT Scan?

Brain PET-CT is a combination of two types of imaging. After patients receive a small tracer dose of radioactive material, PET reveals brain regions with higher or lower glucose metabolism. The high spatial resolution of CT helps to determine the location of these areas. In combination, the PET and CT images can help physicians evaluate both patterns of tracer uptake/metabolism and the actual brain structure.

Why Is a Brain PET-CT Scan Done?

Functional brain information may be indicated, and a PET-CT may be used to obtain an image of the brain. It can assist the doctor in assessing the following clinical situations depending on the type of tracer used:

• Certain types of dementia and cognitive decline
• Alzheimer's disease and other neurodegenerative disorders
• Epilepsy, particularly when the area responsible for seizures needs further evaluation
• Brain tumours in selected situations
• Changes in brain metabolism associated with certain neurological conditions

The specific indication for the test is dependent on the exam indications, based on the patient's symptoms, medical history, and PET tracer type employed.

How Does Brain PET-CT Work?

A PET scan typically uses a radioactive tracer called fluorodeoxyglucose (FDG) that is similar to glucose. Cells in the brain normally consume glucose as their fuel; different parts of the brain may consume glucose at different rates. Once administered, the tracer moves through the bloodstream and is absorbed by the tissues. The PET scanner is able to measure the radiation coming from the tracer and display the distribution of the tracer. The CT can give detailed anatomical information, and the PET information can be correlated with different areas of the brain.

Brain PET-CT Procedure

The brain PET-CT procedure usually involves several steps.

1. Patient Preparation

Preparation depends upon the type of tracer used. In an FDG PET-CT, patients might be advised not to eat for several hours prior to the exam. Water is permitted in general, but specific instructions must be given. Blood glucose is also measured before the FDG scan since inaccurate glucose levels could impact the quality of the image and how it is interpreted.

2. Administration of the Tracer

Trace amounts of a radioactive substance are given in the body, typically intravenously.

3. Resting Period

Once the patient has received the tracer, they normally lie still for a certain amount of time to allow the tracer to distribute correctly. Patients are generally advised to rest quietly and avoid unnecessary physical activity, talking, and major movements during the uptake period.

4. PET-CT Imaging

The patient is positioned on the PET-CT scanning table that is rolled through the PET-CT scanner. The patient should remain still during image acquisition. Usually, the CT component is conducted first or in conjunction with the combined scanning protocol, followed by PET.

How Long Does a Brain PET-CT Take?

This scan of a brain may take a different amount of time to complete depending on the tracer, protocol, preparation, uptake period, and scanning requirements. An FDG scan may require approximately 30-60 minutes for the tracer uptake to occur. The actual imaging time varies depending on the protocol. Additional time is needed for registration, preparation, and instructions for the patient after the scan.

What Can a Brain PET-CT Show?

Brain PET-CT can reveal how active various parts of the brain are. Depending upon the condition being evaluated, metabolism changes can give additional information which complements clinical evaluation and other imaging tests. For instance, some neurodegenerative diseases have specific metabolic activity decreases in specific regions. During epilepsy evaluation, areas of reduced glucose metabolism between seizures may help identify a possible seizure-onset region. PET-CT findings should be interpreted together with the patient's symptoms, medical history, and other relevant investigations.

Brain PET-CT and Alzheimer's Disease

In carefully selected individuals who have cognitive dysfunction, PET imaging of the brain may be useful when further information is required in the evaluation process. In some neurodegenerative disorders, FDG PET can demonstrate a characteristic pattern of abnormal brain glucose metabolism that can help differentiate some types of these disorders. 

Depending on clinical needs and availability, other special PET tracers can be used to provide information on particular biological features. PET-CT findings do not establish a diagnosis in every patient and must be interpreted with clinical and other imaging findings. Interpretation of the findings must be performed by an appropriately qualified specialist, in relation to the patient's clinical picture.

Brain PET-CT for Epilepsy

Brain PET may be used in selected patients with drug-resistant epilepsy, particularly during presurgical evaluation. Between seizures, areas of reduced glucose metabolism may help identify a possible seizure-onset region. PET may be used in addition to MRI, EEG, and other tests to make a full evaluation.

Is Brain PET-CT Safe?

PET-CT involves exposure to a relatively small amount of ionising radiation from the radioactive tracer and CT scan. The radioactive tracer naturally loses its radioactivity and is eliminated from the body, mainly through urine. Patients should inform the healthcare team if they are pregnant, may be pregnant, or are breastfeeding before the examination. The medical team provides specific instructions based on the examination and tracer being used.

What Happens After the Scan?

Most patients can return to their usual activities after a PET-CT unless their healthcare provider gives different instructions. Drinking water after the examination may help promote elimination of the tracer through urine. Patients should follow any specific post-scan instructions provided by the imaging centre.

Diagnostic Imaging at Molecular Diagnostics and Therapy

At Molecular Diagnostics and Therapy, brain PET-CT imaging is available as part of advanced diagnostic services. The examination is performed according to the clinical requirement and appropriate imaging protocol. The results are interpreted along with the patient's symptoms, medical history, and other available investigations to support clinical decision-making.

Conclusion

Brain PET-CT enables detailed information about brain metabolism and structure to be provided by utilising both functional PET imaging and anatomical CT imaging. It can provide additional information during the clinical evaluation of neurological disorders, cognitive decline, epilepsy, and selected brain tumours. The procedure generally includes tracer administration, a resting or uptake period, and image acquisition. Depending on the tracer, the examination may take a different amount of time for preparation and scanning.

If your doctor has recommended a brain PET-CT scan, always follow the instructions given to you by your healthcare team to prepare for the scan, and discuss any medications, diabetes, pregnancy, or breastfeeding before having your scan. The PET-CT services at Molecular Diagnostics and Therapy are done using advanced PET imaging technology and clinical protocols for brain PET.