What is SPECT Imaging?

SPECT stands for “Single Photon Emission Computed Tomography.”  It is a sophisticated nuclear medicine study that measures the cerebral blood flow and activity patterns of your brain.  It utilizes a radiopharmaceutical to create images of actual brain function by identifying blood flow patterns throughout the brain.  These images assist your doctor in making a more accurate diagnosis and treatment plan for you.  Most of our patients find that being able to “see” the areas of their brain that are contributing to their symptoms gives them a much better understanding of their condition and increases motivation to comply with their treatment recommendations.
The study is performed by injecting a very small dose of a radioactively tagged compound (Ceretec) that is taken up by the brain.  Once in the brain the Ceretec emits energy for the next few hours.  The cameras in the SPECT scanner slowly rotate around your head and detect this energy in the form of light.  The most active brain cells will emit the most energy and the least active ones will emit the least energy.

How is a brain SPECT scan different than a CT or MRI scan?

CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) look at the brain’s structure (anatomy).  SPECT imaging assesses the brain’s blood flow (functioning).  In many cases the brain’s structure may be normal, while the functioning is abnormal.  In psychiatry the majority of CT’s and MRI’s ordered on our patients are found to be normal, yet their symptoms persist.  Psychological problems often reveal abnormalities with the brain’s functioning as opposed to its anatomy.

Consider this analogy—if you were flying in an airplane today you would want to know that the engine was working right.  Taking a picture of the engine (CT/MRI) shows you all of the parts, but does not give you any information about how well the engine is running (functioning).  A brain SPECT image identifies important information about your brain’s functioning.  Identifying an areas of abnormal functioning can be vitally important in helping you doctor make the best diagnosis and treatment plan for you.

What’s the reason for a brain SPECT?

SPECT imaging is a clinically useful way to look at brain functioning.  Certain mental and behavioral states can be correlated with certain SPECT patterns.  Gathering this information from the SPECT studies will help you and your doctor understand your specific brain functioning, which may help further in your evaluation and treatment.

Thomas Insel M.D. Phd, Director of the National Institute of Mental Health, the top psychiatrist in the nation, said in 2005 “Brain imaging in clinical practice is the next major advance in psychiatry.”  He believed that brain imaging in clinical practice would be a reality within 5 years.  Indeed, today we are beginning to see his predictions come to pass.

What are reasons for ordering a SPECT study?

Here are some of the most common ones:

• Evaluating memory loss, suspected dementia, or other cognitive problems
• Evaluating the effects of recent or past brain trauma (from mild to severe)
• Evaluating aggressive and/or violent behavior
• Evaluating the presence of an underlying organic condition in the brain (such as brain trauma or dementia) that contributes to emotional, behavioral, or learning disturbances
• Evaluating cerebral cardiovascular disease
• Evaluating treatment resistant or atypical psychiatric conditions
• Evaluating the specific brain patterns underlying mood disorders, anxiety disorders, and attention deficit disorders
• Evaluating the extent of impairment that drugs, alcohol, or other toxins have done to the brain
• Evaluating the physiological effects of treatment—this is often done with follow-up scan(s)

Will a SPECT study give me an accurate diagnosis?

No.  A SPECT image by itself will not give an accurate diagnosis.  SPECT images help clinicians understand more about the specific functions of your individual brain.  Your brain is unique and this may lead to unique responses to your treatment plan.  This helps explain why two people that have depression can both get the same treatment and one get better while the other gets worse.

Diagnosing specific psychiatric conditions is done through clinical history, personal interview and information from families, SPECT images, checklists, and other neuropsychological tests.  There is no study that is a “doctor in a box” that can give an accurate diagnosis on individual patients.

How is a SPECT procedure done?

An evaluation consists of two scans which are performed at least 24 hours apart.  The concentration scan is usually performed first.  For this one the patient (who is in a testing room) is given a task that requires prolonged concentration.  While the patient is engaged in this task the imaging agent is injected into the patient’s arm through a small IV line.

When the task is finished the patient then lies on a table and the SPECT camera rotates around his or her head.  Patients do not have to go inside of the tube to have the scan performed.  The scanning time is 20-30 minutes.
For the resting scan the patient relaxes in a quiet room and the imaging agent is given through the small IV line.  This is again followed by the patient lying on the SPECT scan table.

What side effects are there?

 People do not have allergic reactions to the tracer.  Sometimes a small amount of ethylene blue dye is added to the Ceretec.  The possibility exists that a very small percentage of patients may experience a mild rash, facial redness and edema, fever, and/or a transient increase in blood pressure.

The radiation exposure from one brain SPECT study is approximately the same as that of one abdominal x-ray or about two-thirds that of a CT scan.  Very rarely, patients have reported a green colored tint to their urine for a day or two following the procedure.

The half-life of the technetium 99m in Ceretec is 6 hours; therefore it is almost completely cleared out of your system within 24 hours.

Where can I find more information about brain SPECT imaging?

Brainplace.com has over 2,000 scientific articles and abstracts on brain imaging.  New studies are continually added as they become available.  You can also see over 300 SPECT images here.