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Brain scan

What is a Brain Scan?

A brain scan is a specialized imaging test that uses small amounts of radioactive materials (tracers) to evaluate brain function. Unlike CT or MRI scans that primarily show brain structure, nuclear medicine brain scans show how the brain is working at the cellular level. These scans can detect abnormalities in brain function even before structural changes become visible on other imaging tests.

Types of Brain Scans

FDG PET Brain Scan

What it shows: Glucose (sugar) metabolism in the brain Used for:

  • Alzheimer’s disease and other forms of dementia
  • Differentiating between types of dementia
  • Evaluation of seizure disorders
  • Brain tumor assessment
  • Early detection of neurodegenerative disorders

FDG (fluorodeoxyglucose) is a radioactive form of glucose that shows which areas of the brain are using energy. Areas with reduced uptake may indicate decreased brain function, which helps identify patterns specific to different types of dementia.

HMPAO (Ceretec) Brain Scan

What it shows: Blood flow to different regions of the brain Used for:

  • Alzheimer’s disease and vascular dementia
  • Stroke evaluation
  • Brain death assessment
  • Seizure focus localization
  • Traumatic brain injury assessment

HMPAO (Hexamethylpropyleneamine oxime) is a tracer that measures cerebral blood flow. Since brain activity and blood flow are closely linked, this scan can identify areas of the brain that are receiving inadequate blood flow or functioning abnormally.

F-18 DOPA Brain Scan

What it shows: Dopamine production and pathway function Used for:

  • Parkinson’s disease
  • Other movement disorders
  • Distinguishing Parkinson’s from similar conditions
  • Evaluating response to treatment

F-18 DOPA is a radioactive form of L-DOPA (a precursor to dopamine) that shows the function of dopamine-producing cells in the brain. This is particularly useful for evaluating the nigrostriatal pathway, which is affected in Parkinson’s disease and related disorders.

How Do Brain Scans Work?

Brain scans work by:

  1. A radioactive tracer is injected into your bloodstream
  2. The tracer crosses the blood-brain barrier (a protective barrier between your bloodstream and brain)
  3. The tracer accumulates in active brain cells
  4. A special camera detects the radiation emitted by the tracer
  5. A computer creates detailed 3D images showing brain function

Different tracers are designed to measure different aspects of brain function, allowing doctors to select the most appropriate scan for your specific condition.

Why Might I Need a Brain Scan?

Your doctor may recommend a brain scan to:

  • Help diagnose various types of dementia (including Alzheimer’s disease)
  • Differentiate between types of dementia when symptoms overlap
  • Evaluate movement disorders like Parkinson’s disease
  • Locate the origin of seizures
  • Assess brain function after a stroke or injury
  • Monitor response to treatment
  • Help with surgical planning

Preparing for Your Brain Scan

Before Your Appointment

  • Continue taking your regular medications unless instructed otherwise
  • Inform your doctor if you:
    • Are pregnant or breastfeeding
    • Have diabetes (special preparation may be required for FDG scans)
    • Have claustrophobia (fear of enclosed spaces)
    • Have had other nuclear medicine tests recently

Specific Preparation for Different Scans:

For FDG PET Brain Scan:

  • Fast for 4-6 hours before your appointment
  • Avoid strenuous exercise for 24 hours before the scan
  • Avoid caffeine for 24 hours before the scan
  • Your blood glucose levels will be checked before the scan

For HMPAO Brain Scan:

  • No special dietary restrictions
  • Avoid caffeine for 24 hours before the scan
  • Avoid alcohol for 24 hours before the scan

For F-18 DOPA Brain Scan:

  • You may be asked to stop certain medications temporarily
  • Specific instructions will be provided based on your medications
  • You may need to follow a low-protein diet the day before the scan

What to Expect During the Procedure

Before the Scan

  1. An IV line will be placed in a vein in your arm
  2. You’ll be taken to a quiet, dimly lit room to minimize brain stimulation
  3. You’ll rest for about 10-15 minutes before the tracer is injected
  4. The radioactive tracer will be injected through your IV
    • This feels similar to having blood drawn
    • The tracer will not make you feel different or cause side effects

During the Uptake Period

  1. After injection, you’ll need to remain in a quiet environment for:
    • FDG PET scan: 30-60 minutes
    • HMPAO scan: 60-90 minutes
    • F-18 DOPA scan: 60-90 minutes
  2. You’ll be asked to relax and avoid reading, talking, or other activities that stimulate the brain
  3. This resting period allows the tracer to distribute throughout your brain

During the Imaging

  1. You’ll lie on an examination table with your head positioned in a special holder
  2. For gamma camera scans (HMPAO):
    • The camera will rotate around your head
    • The imaging takes about 20-30 minutes
  3. For PET-CT scans (FDG or F-18 DOPA):
    • You’ll move slowly through the scanner
    • The imaging takes about 10-20 minutes
  4. You’ll need to lie still during the imaging
  5. The procedure is painless and the camera makes minimal noise

After Your Scan

  • You can resume normal activities immediately
  • Drink plenty of fluids to help flush the tracer from your body
  • The small amount of radiation will naturally leave your body within a day
  • Avoid close con

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