Weight bearing (Standing) magnetic resonance imaging (MRI)
Weight Bearing (Standing) MRI
The weight bearing or standing MRI is a revolutionary MRI scanning technique that allows imaging of the spine while the patient is in the standing or load bearing position. Often lower back pain is more pronounced when patients are in the standing position and neck pain exacerbated when the neck is flexed or extended. The design of our new weight bearing MRI scanners allows patients to stand during the exam and therefore we can visualise the lower spine in the position where pain is experienced the greatest. In the neck we can scan in flexion and extension which is something that cannot be performed on a conventional MRI where the patient is lying down.
There are sometimes noticeable changes in the neck and lower spine when comparing scans performed in the recumbent position to the erect position. This is because there are significant bio-mechanical changes in the spine when going from a lying to a standing position or when flexing or extending the neck. The new weight-bearing MRI scanners based at our Epping and Frankston clinics will allow the radiologist to compare images in different positions and assist them in determining whether pathology is better visualised as the spine is put under gravitational loading or when the spine is flexed or extended.
It is recommended that you undergo a conventional MRI in the first instance as this test provides exceptional image quality and is the gold standard in terms of assessing the spine. However if the conventional MRI diagnosis does not correlate with your back or neck pain, a weight bearing scan may add value by demonstrating postural pathology better. In particular, if pain is worse when standing or when the neck is flexed or extended, then a weight bearing scan can assess the injury in these positions. Your doctor may refer you to have a weight-bearing MRI to determine if there are any changes in the diagnosis compared to your initial conventional MRI.
The MRI procedure will be thoroughly explained to you, and your safety questionnaire reviewed and discussed before you enter the scan room. If you have any questions, please ask the radiographer (medical imaging technologist), who will be operating the MRI scanner, as it is important that you are comfortable and know what will be happening.
You will usually be asked to change into a gown to avoid items in your pockets not being accidentally taken into the scan room.
You will be asked to lie on the scan table and given a buzzer to hold. When you squeeze it, an alarm sounds in the control room and you will be able to talk to the radiographer.
The MRI scanner is very noisy during the scans. It is at a noise level that can damage your hearing. You will be given earplugs or headphones to reduce the noise to safe levels.
Depending on the type of MRI you are having and your particular situation, at this point you might have:
- leads placed on your chest to monitor your heartbeat if having a heart scan
- a small plastic tube (pulsoximeter) taped on your finger to check your breathing and heart rate if having sedative (calming) medication
- a needle inserted into a vein in your arm if any medication is required during the scan.
If you are claustrophobic and find you are unable to proceed with the scan, a sedative can be injected.
The most common medication injected is called Gadolinium contrast medium (contrast). This highlights the part of the body being scanned, which can give more information to the radiologist who is assessing your problem. Other medication might be injected; for example, to slow down your intestinal movement if having an MRI of the rectum.
The part of your body to be scanned will be carefully positioned and gently secured, so you are comfortable and more likely to remain still. Special antennae (coils) will be positioned around it to pick up signals from your body so the computer can create images. The coils are usually encased in a plastic pad or frame. Depending on the part of the body being scanned, they might be wrapped around your shoulder or lie on top of your stomach. Some coils are in the mattress of the scan bed, used when your back is being scanned.
To ensure the quality of the images captured, it is very important to be still.
The scan table will then move into the centre of the machine. Your head might be inside or outside the scanner, depending on the part of the body being scanned.
When the scan begins, you will hear a knocking noise that continues during each scan. Scanning is not continuous, and each scan varies in length from about 1 to several minutes, with a break in between. You will be able to talk to the radiographer between each scan and can press the buzzer if you are not comfortable or want to come out of the machine at any time.
The scanning process is painless. You might feel warm during scanning. If you do feel anything at all, it is important you tell the radiographer.
You need to lie still and hold your position during the scan. In general, you can breathe normally, but occasionally, during some types of MRI, you will need to hold your breath. Breathing and movement can make the images blurry and assessment of your problem more difficult.
The Radiographer is there to ensure that the scan is carried out safely and correctly, to get the highest quality images. However they won’t be able to advise you of the result, as your images need to be assessed by the Radiologist (specialist doctor) who will provide a written report.
The scan can take between 10 to 30 minutes to complete, depending on the part of the body being imaged and the type of MRI required. The radiographer will advise how long your scan will take. Occasionally, you might need to return for delayed scans, usually after 1 or 2 hours, mostly with scanning of the liver. If you received sedative medication, this will increase the time you will need to stay at the MRI facility.
A MRI has no known long-term harmful effects, provided the safety precautions are followed. MRI does not use radiation, and is therefore of significant benefit to younger people and children, and can also be used safely in pregnancy, if required. MRI is capable of providing your doctor with a wide range of information about your body and particular diseases or conditions you might have, and can show certain conditions that other tests can’t. MRI can image most parts of the body in any direction to obtain maximum information and provides this information in high-quality images.
There are no known side-effects of an MRI, providing you do not have any implants or objects that must not go in the scanner.
The danger from the MRI is due to interactions of objects with magnetic fields. Metal objects can move, as well as get hot, and electrical currents can be produced and lead to malfunction of a device. A strong magnet can alter or wipe information from other magnetic devices. Some of these interactions can cause harm or death.
Metal objects that are attracted to magnets can be pulled rapidly, like a missile, into the MRI machine. These can damage the machine, as well as injure anyone in the way.
Other metal in your body might move if not well fixed. These would include metal fragments in your eyes, which can interfere with vision if they move in the MRI, and magnetic dental implants. Most implants (hip replacements for example) are well fixed, and are usually made of non-magnetic or only weakly magnetic materials and are not a problem. Clips in the brain, used on an aneurysm, must be non-magnetic or they cannot be scanned. Some catheters (fine tubes usually in your blood vessels) can also melt if they contain a wire.
If you are pregnant, please tell our clinic staff before your procedure. This will not necessarily stop you from having the scan. There are no reported effects of an MRI on the unborn child, but caution is always used in pregnancy.
If you are required to have an injection of contrast, there is a very small risk of an allergic reaction. Contrast is generally very safe, but as with all medications, allergic reactions can occasionally occur. Our clinic staff will treat you if you have an allergic reaction.
If you have a history of kidney disease, you should have a blood test before the scan to ensure that the contrast can be given safely. Please ask the MRI radiographer if you have any concerns.
Your doctor will receive a written report on your test as soon as is practicable.
It is very important that you discuss the results with the doctor whom referred you so that they can explain what the results mean for you.
This information is credited to Inside Radiology, Royal Australian and New Zealand College of Radiology (RANZCR). insideradiology.com.au June 2014