CT Scan vs MRI: Brain Scan Types and Which To Choose

MRI and CT scans are different medical imaging techniques that can create detailed pictures of the brain. If you’re struggling with neurological issues or a head injury, or you’re worried about brain-related symptoms, a brain scan can help your clinician diagnose potential problems. We’ll guide you through the key differences between these two brain scan types, what each can show and how long each procedure takes. So, if you’re unsure whether to choose between a CT scan or an MRI scan for brain health, we can help you decide which one is best for you.

Why might I need a brain scan?

Your clinician may recommend having a brain scan for several different reasons. Here are some of the most common:

• Symptoms: You are experiencing unexplained neurological (disorder of the nervous system) symptoms, such as headaches, seizures, problems with hearing or vision, or loss of motor skills such as walking or speaking.

• Monitoring of particular conditions: Your clinician suspects you may have a neurological condition, such as epilepsy, Alzheimer’s or Parkinson’s. Or you may already have a diagnosed condition, and your clinician wants to monitor its progression. 

• Injury or trauma to the head: You have a head injury, and your clinician wants to check for complications such as skull fractures, internal bleeding, blood clots or bruised or swollen brain tissue. 

• Cancer diagnosis: You may have a primary brain tumour or a secondary brain tumour which has spread from another part of the body (metastatic cancer).

• Stroke diagnosis: You have a suspected stroke and your clinician needs to find out if it is the result of a blood clot or a bleed.

• Pre-surgery check: You may have cancer, and your clinician wants to check the spread of the disease before operating, for example, checking the spread of breast cancer before surgery.

• Family history: You may have a higher risk of brain aneurysms (swollen or bulging blood vessels) because two or more close relatives have had a brain aneurysm (familial aneurysms).

What is a CT scan and how does it work?

A CT (computed tomography) scan is a low-risk x-ray that takes cross-sectional pictures. It uses an X-ray beam that spins around you, rapidly taking pictures from different angles. A computer then combines all these pictures and turns them into three-dimensional images showing slices of the area, such as the skull, blood vessels or soft tissues. Unlike a regular X-ray, which is a 2D image, a CT scan gives your clinician a detailed model of your brain. This can help them to diagnose issues and causes of symptoms more accurately. 

What is an MRI scan and how does it work?

An MRI (Magnetic Resonance Imaging) scan takes detailed three-dimensional images of organs and tissues using powerful magnetic fields and radio waves. The magnets align water molecules in your body first; then, the radio waves knock them out of position. When the molecules realign, they give off signals based on their location. A computer translates those signals into a detailed picture. Unlike X-rays, an MRI uses no radiation. The magnetic fields and radio waves create the images slice-by-slice without pain, contrast dye, surgery or special equipment. Soft tissues like the brain show up exceptionally clearly. 

What does a brain scan show?

It’s understandable that you might have questions about whether to choose CT or MRI for brain imaging, or be wondering what can a CT scan show that an MRI cannot. Keep reading to find out the answers.

What does an MRI scan of the brain and head show?

An MRI scan of the brain and head gives very clear views of soft tissues, which can help diagnose tumours, damage, and neurological conditions. It can show detailed brain images, including veins and arteries, the four different lobes within the brain, the central cortex, and the brain stem. 

MRI scans are better at providing clear images of abnormal tissue because of the high level of detail in the images they capture. They can help to diagnose abnormalities like tumours, strokes, infections, blood clots, swelling, fluid buildup, and other problems.

What does a CT scan of the brain and head show?

Like an MRI, a CT scan of the brain and head can show similar parts of the brain but is better at producing pictures of skeletal structures such as the skull. So, you’re more likely to have a CT scan after an injury. 

Can a CT scan detect a brain tumour?

CT scans can also detect brain tumours accurately, so they are often used for diagnosis, as well as before and after cancer treatment to see how well a tumour has responded.

How long does a brain scan take?

Both CT and MRI scans involve you lying as still as you can on a flat bed. With a CT scan, a ring-shaped machine will move quickly around your head to take the images. With an MRI brain scan, you’ll be moved (usually head-first for a head and brain scan) into a large cylindrical tunnel to lie very still while the signals create intricate and clear pictures of the body, slice by slice.

The difference in how both scans capture images means that CT scans last just a few minutes, while MRI scans take much longer, anywhere from 15 minutes to an hour and a half, depending on what part of the body is being scanned and whether you move during the scan.

Which is better - an MRI or CT scan for brain health?

Neither scan is ‘better’ than the other. CT scans and MRI scans have different risks and benefits, which can help you and your clinician decide which one to choose:

• Like X-rays, a CT scan involves exposure to ionising radiation, which carries a risk to health if you have repeated scans (although this risk is very small). If your clinician or radiologist thinks you’ll need multiple scans, they may consider an MRI scan to be a safer option. 

• If you have metal implants or devices in your body that aren’t compatible with MRI scans, it may be safer for you to have a CT scan. 

• If you have claustrophobia or are anxious about being in confined spaces, your radiologist may recommend a CT scan, as it’s quicker and less confining than an MRI scan. Similarly, if you have a condition where you struggle to stay still, a CT scan may be a better option for you.

• Because of how quick they are, CT scans are more commonly used for head traumas and fractures where you need medical treatment quickly.

CT scan vs MRI scan brain imaging: which to choose?

Don’t worry if you’re still not sure about which scan is best for you, or the difference between MRI and CT scan of the brain. All Scan.com bookings include two clinical consultations. One happens before the scan to ensure your clinician recommends the best scan for you, and weighs up the CT vs MRI brain scan decision in light of your individual circumstances. The second consultation takes place after the scan, where your clinician will clearly explain the results and the next steps. 

How to get a brain scan near you

Skip the NHS waiting lists and book a private MRI scan or private CT scan near you today with Scan.com. We can help you fast-track your diagnosis and treatment without GP referrals. Instead, you’ll have expert clinical consultations within days. Choose from over 150 centres nationwide with flexible appointment times and get fast online results, including a digital imaging report. It’s easier than ever to get your health back on track.

Sources:

Brain aneurysm. (2022). https://www.nhs.uk/conditions/brain-aneurysm/

CT scan. (2023). https://www.nhs.uk/conditions/ct-scan/

CT scan vs. MRI: What’s the difference? (2023). https://www.mdanderson.org/cancerwise/ct-scan-vs-mri--what-is-the-difference.h00-159616278.html

MRI scan. (2022). https://www.nhs.uk/conditions/mri-scan/

Stroke. (2022). https://www.nhs.uk/conditions/stroke/

Stroke: Diagnosis. (N.D.) https://www.nhs.uk/conditions/stroke/

Traumatic brain injury. (2021). https://www.mayoclinic.org/diseases-conditions/traumatic-brain-injury/diagnosis-treatment/drc-20378561

Which is Better for Brain Imaging: MRI vs CT Scan? (2023). https://tischbraintumorcenter.duke.edu/blog/which-better-brain-imaging-mri-vs-ct-scan