Brain Imaging: Functional MRI vs. SPECT Scans—What’s the Difference?

Functional MRI

There are many types of brain imaging— a veritable alphabet soup that includes CT, MRI, fMRI, and SPECT—so it can be confusing to know which one is best for your specific concerns. An easy way to demystify this is by understanding that imaging is generally divided into two categories. One looks at structure, kind of like the architecture of the body or its specific parts, and the other is function, which tells your doctor how the parts are working.

The Basics of Structural Brain Imaging

Two of the most common types of structural brain imaging are computed tomography (CT or “CAT” scan) and magnetic resonance imaging (MRI). After a head trauma, stroke, or because of severe headaches, a CT or MRI is often done to assess the integrity of the brain’s anatomy. These procedures can identify if any parts of the brain are abnormal in size, if anything is missing, or if something is there that shouldn’t be, such as a blood clot or tumor.

The Big Difference Between Structural and Functional Brain Imaging

What the structural imaging procedures do not provide is detailed information about how a brain is actually working. This is where functional brain imaging comes in. This type of advanced camera technology is utilized to see how a brain functions by assessing the blood flow and activity in the brain.

There are a few different types of cameras and procedures that are used to do this imaging, and two of them are:

  • SPECT—which stands for single-photon emission computed tomography
  • fMRI—or functional magnetic resonance imaging

Both modalities provide a lot of detailed information about how well the various areas of the brain work, but there are some big differences in the way they can do this.

How fMRI Works

The technology for fMRI was developed in the early 1990s, and it allows researchers and doctors to see the activity in specific areas of the brain. For the procedure, the patient lies inside a tube that has a powerful magnet that is 10,000 times stronger than the earth’s magnetic field. In a nutshell, fMRI can construct detailed pictures of the brain by combining radiofrequency energy waves and magnetic fields that interact with the magnetic properties in the water molecules of our blood. These real-time images show activity—or blood flow—to certain areas in the brain in response to a particular task.

Depending on what brain functions are being assessed, the patient will be given a specific task to do such as mentally reacting to something with thoughts or feelings. The areas that are activated by the task will “light up” and be captured during the imaging.

However, one of the biggest challenges with using fMRI is that each task looks at only a particular area or circuit in the brain. So for example, if a person had a head injury, each area of the brain that is of concern would have to be assessed with a different task to activate it. Depending on a patient’s symptoms, the doctor might want to analyze the function of these 7 parts of the brain:

  • Prefrontal, dorsal lateral frontal, and orbital frontal cortex
  • Right and left temporal lobes
  • Cerebellum
  • Occipital lobe

And although the blood flow information that is obtained can be very helpful, using fMRI to do this can be quite time-consuming and expensive. Brain SPECT, on the other hand, can reveal blood flow and activity of the whole brain with just a single scan. Here’s why.

How Brain SPECT Works

Like fMRI, brain SPECT imaging is used to evaluate blood flow and activity throughout the brain. A SPECT scan provides 3 important pieces of information:

  • Areas of the brain that work well
  • Areas that are underactive
  • Areas that are too active

SPECT is a nuclear medicine procedure that has been used by the doctors at Amen Clinics for more than 30 years to help them more clearly understand the function of their patients’ brains.

The SPECT Scan Process is Easy

To prepare for the imaging, a patient will sit in a quiet room and a little IV will be placed in their arm. An imaging solution with a very small amount of a radioactive tracer is inserted into the IV The solution does not have iodine, so rarely does anyone have an allergic reaction to it. The tracer is taken up into the brain cells within a few minutes of the injection and creates a “snapshot” of the patient’s brain activity.

About 30 minutes after the injection, the patient will be taken into the camera room and lie down on the imaging table for about 20 minutes while the camera’s detectors rotate around their head—patients do not have to go into a tube. The camera gathers data from the “snapshot” of brain activity created from the injection.

Once the images have been processed, they are read by a highly skilled physician who writes a detailed report about the patient’s brain function. At Amen Clinics, this information is then evaluated by the doctor, along with other testing and the patient’s clinical history, to create a comprehensive treatment plan for the patient.

Brain SPECT Scans Provide Important Information

Because SPECT looks at the function of the entire brain, a single SPECT scanning process can provide important details about the biological underpinnings of symptoms. For example, if a patient has depression, without looking at the brain it would be hard to know if it is being caused by:

  • An undiagnosed head injury
  • Toxic exposure
  • Inflammation or infection
  • Overactive limbic area
  • Underactive prefrontal cortex
Because SPECT looks at the function of the entire brain, a single SPECT scanning process can provide important details about the biological underpinnings of a patient’s symptoms. Click To Tweet

SPECT scans are an efficient and relatively simple way to identify any abnormal patterns in the brain that are driving a patient’s symptoms. Recently, the Canadian Association of Nuclear Medicine published their new practice guidelines which endorse the use of brain SPECT imaging for the assessment of:

Both fMRI and SPECT are fascinating tools of medical imaging technology. And while each assess brain activity, in the clinical setting, fMRI is largely used to look at specific areas of brain function as they relate to surgery planning and risk for the biopsy or removal of brain tumors or for epilepsy surgery.

SPECT, on the other hand, is used to identify abnormal brain function that contributes to a multitude of neurological and psychiatric disorders, thereby providing valuable information that greatly improves patient outcomes.

Mental health issues can’t wait. At Amen Clinics, we’re here for you. We offer in-clinic brain scanning and appointments, as well as mental telehealth, remote clinical evaluations, and video therapy for adults, children, and couples. Find out more by speaking to a specialist today at 888-288-9834 or visit our contact page here.


  1. How much does a SPECT scan cost and is it covered by insurances?

    Comment by Edward Chastka — August 25, 2021 @ 4:00 AM

  2. It will be a blessing to have a Psychiatrist who knows ; that one treatment out the med dictionary doesn’t help everyone that is like putting ointment on a sore without cleaning w/antibiotic first then piling other meds on and you really haven’t got the glass out the scratch.

    Comment by Bobbie — August 25, 2021 @ 5:47 AM

  3. How many hospitals or clinics are doing SPECT scans and are there any in Omaha NE. if not what is the closest place.

    Comment by jeffery otte — August 25, 2021 @ 6:24 AM

  4. Is there a place in San Antonio TX that I can ho to for this spect ?
    And a park park cost
    I’m limited by social security funds

    Comment by Sandra Baker — August 25, 2021 @ 8:51 AM

  5. Hello Sandra. We opened up a clinic in the Dallas Metro Area in the beginning of the year ( For more information about cost, financing options, insurance, and scheduling, please contact our Care Coordinators:

    Comment by Amen Clinics — August 25, 2021 @ 9:00 AM

  6. Hello Jeffery, thank you for reaching out. Amen Clinics currently has 9 locations: If you’re unable to travel to one of our locations, our Care Coordinators may be able to assist you with resources or referrals closer to you. For more information, please contact our Care Coordinators:

    Comment by Amen Clinics — August 25, 2021 @ 9:01 AM

  7. Hello Edward, thank you for reaching out. For information regarding pricing, insurance, and financing options, please contact our Care Coordinators:

    Comment by Amen Clinics — August 25, 2021 @ 9:02 AM

  8. You should range cost of scans.

    Comment by Robert Smutko — August 25, 2021 @ 9:11 AM

  9. Thank you for the article and elaboration.

    Comment by Genea — August 25, 2021 @ 9:38 AM

  10. The distinction between Spect and MRI very helpful for me.,Also I have a pacemaker so could not have an MRI. At 93 I still want a scarf it can work out’

    Comment by Robert Bettinger — August 25, 2021 @ 11:50 AM

  11. When you sit in the quiet room for 30 minutes for the IV, can you read, sleep, text – what is recommended? Or does it matter what your mind is doing as long as you are sitting still?

    Comment by Merrie VonSeggern — August 25, 2021 @ 1:16 PM

  12. I highly recommend the SPECT brain scan. I had it done twice and my health insurance covered it through a preauthorization. Dr Paul Harch was my HBOT physician in NOLA though I live in IA. It was well worth the travel. Now if only health insurance would cover HBOT for brain injuries.

    Comment by Mary B Underwood — August 25, 2021 @ 3:42 PM

  13. My daughter who is 17 has recently been diagnosed with a myriad of disorders including depression on top of her previous diagnoses of PTSD, ADHD, Anxiety, and Dyslexia. Every doctor prescribes more or different meds including Abilify which caused significant spasms, twitches and neuropathy. The neurologists give a cursory physical exam and she has had several neuropsychological exams but they are not willing to do anything further. She is being used as a guinea pig and we have been told her illness may likely develop into Borderline Personality Disorder. She recently had a negative CAT scan after a serious head injury, but as you are aware that doesn’t tell me much considering her symptoms. I do not have a problem with medication, but she needs a SPECT Scan. Can she get scanned while on medication or does she need to come off her meds for a period of time?

    Comment by marilyn bell — August 25, 2021 @ 7:10 PM

  14. Hello Marilyn, thank you for reaching out. We’d be happy to contact you directly with more information. In the meantime, here are some frequently asked questions:

    Comment by Amen Clinics — August 26, 2021 @ 9:10 AM

  15. Where can I do this in Belgium Europe?
    Never found any info here with psychiatrists, clinics…
    Thank you so very much

    Comment by christine — August 27, 2021 @ 4:25 AM

  16. My daughter has dystonia. She is only 17. Can she still have a spec of her brain ran? With the deep brain Stimulator in?

    Comment by Angie Amato — August 28, 2021 @ 7:28 PM

  17. Hello Angie, thank you for reaching out. We’d be happy to contact you directly to provide more information about brain SPECT scans and our services for your daughter. We look forward to speaking with you.

    Comment by Amen Clinics — August 30, 2021 @ 1:21 PM

  18. Lucky (to be alive), Ken would like to know how to source resources in Peterborough, Ont re a SPECT MRI? I survived a 30’ fall (which ended on asphalt, after a concrete parking block). Additionally, I had a heart attack, Never has been a solidly defined cause but, MVD (Micro Vascular Disease), keeps coming up in relation to other issues.

    Would a SPECT MRI be the best tool to provide quality data or info. for doctors to work with in assisting me with the challenges listed above?

    Thanking you now for your attention to my challenges. Ken F. Robock. Peterborough, Ont.

    Comment by Ken — August 29, 2023 @ 9:19 AM

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