Magnetic resonance imaging (MRI) reveals the structure of the head and brain and identifies any abnormalities. An MRI uses powerful magnet and radio waves fed into a computer to create the image. The MRI scan is one of a number of imaging techniques that have revolutionised medicine. It is currently the most sensitive imaging test for the head and brain.
What is a MRI scan for?
MRI is a diagnostic tool that produces detailed pictures of soft tissue, organs and bone structure. For people with suspected Alzheimer's disease an MRI brain scan can:
- Exclude other diseases that can cause similar symptoms such as brain cancer, stroke, damage that results from a traumatic brain injury, diseases of the pituitary gland that sits within the brain, and other neurological diseases.
- Document brain abnormalities in patients with dementia's such as Alzheimer's where brain shrinkage and cell atrophy (cell death) can be observed.
- The imaging technique is used to research Alzheimer's disease. For instance, a recent study has looked at how brain size may predict risk for early Alzheimer's disease
Does the MRI Scan Hurt?
No. An MRI imaging scan is not painful. Some people can feel claustrophobic as the table moves into the hole in the middle of the PET machine. If you inform the staff in advance a sedative can be given. For people with Alzheimer's who may be confused or more uncooperative a mild sedative can help minimize any feeling of discomfort and can help them relax.
When a contrast material is injected into a vein in the arm you will feel a small prick and you may feel a slight coldness and a flushing sensation for a minute or two. There may be bruising at the needle site and a metallic taste in the mouth after the test. The contrast is unlikely to cause an allergic reaction.
What Happens in the Test?
The imaging process will not cause any pain itself but keeping still while lying on a hard surface may cause discomfort.
- You have to stay very still during the imaging process. The technician will tell you when it is important.
- The area being scanned can feel slightly warm.
- You will be asked to stay still for the few seconds or minutes when the images are being taken.
- It can be noisy! The machine makes tapping or thumping sounds when the coils that generate the radiofrequency pulses are activated.
- Minimizing anxiety. You can speak to the technician, who can see and hear you from the next room to if you feel anxious. A close relative or friend is often allowed to stay with you once they have been screened for safety in a magnetic environment.
How Long Does MRI Scan Take?
The scan takes about 45 minutes, longer than CT or X-ray
What Happens to the Scan Results
The PET scans will be interpreted by a radiologist or physician specialised and trained in nuclear medicine. Their report of the results will be sent to your referring specialist.
Is the MRI Scan Safe?
MRI is generally considered safe:
- The patient needs to stay very still to get good images. Over sedation can be a problem.
- MRI does not distinguish between cancer and edema fluid.
- Although not generally a problem for people with Alzheimer's, an MRI is not advised during pregnancy even though it is believed no harm comes to the fetus during imaging.
MRIs are not suitable for everyone. They cost more than other types of scans and are not advisable if someone is acutely injured because of the long test time. Equipment the patient may be attached to i.e. life support may present a problem. Overweight, or very large people, may not fit into the opening of a conventional MRI machine.