About MRI Scanning
MRI stands for Magnetic Resonance Imaging and is a means of taking cross-sectional images in any plane of the body. These images are detailed and will clearly demonstrate the body’s soft tissues such as muscles, nerves, spinal cord, intervertebral discs, cartilage, ligaments, etc.
The MRI scanner produces these images by placing the patient within a strong magnetic field and then aiming a pulse of radiowaves into the body. The radiowaves are returned from the body and this signal is the basis for producing an image. This process is completely safe and does not involve any harmful radiation.
At St John & St Elizabeth’s we have the latest 3T Siemens Skyra MRI scanner working alongside our 1.5T scanner.
The Skyra is compact in design and has a flared, open-ended bore to ease the feeling of confinement often found in other high field strength scanners. There is increased space around the patient during the scan and the shorter machine allows the patient’s head to remain outside the scanner during most scans.
The high speed gradient system, advanced scanning sequences and full range of specialised localisation coils, enable complex imaging to be undertaken with increased resolution and shorter scan times.
These advance features enable us to perform:
- High definition musculoskeletal imaging with superb resolution of even small digital structures.
- High resolution “breath-hold” imaging of the abdomen & pelvis, including MRCP and MR Angiography.
- High resolution breast MRI with dynamic assessment of blood perfusion.
- High resolution, thin slice and 3D volume acquisition giving exquisite images of the posterior fossa, acoustic nerves and the middle ear.
- High detail anatomic scanning of the brain and spine.
The short bore and fast scan times are of particular benefit to those who find lying still difficult or who suffer from claustrophobia.
Is MRI suitable for you?
Not everyone can have an MRI scan. The magnetic field from the scan affects metals such as iron, nickel and steel. If you have
- a heart pacemaker
- metal prosthetic heart valves
- aneurysm clips (metal clips on arteries)
- metal pins, rods or screws in your bones
- inner ear implants
- an IUCD (intrauterine contraceptive device) or coil
- body piercing
- shrapnel or gunshot wounds
- had pieces of metal removed from your eyes or head
- any other implant in the body
Your doctor will discuss with you whether it is safe for you to have an MRI scan.
MRI scans are also not usually done on women who are less than 12 weeks pregnant.
About the procedure
An MRI scan is routinely done as an out-patient procedure. The scan can take from 15 minutes to an hour, depending on the examination.
If you are having an abdominal or pelvic scan you may be asked to follow special instructions about eating and drinking. Depending on the part of your body which is to be examined, a dye (contrast medium) may be used to make some tissues show up more clearly. These dyes are harmlessly removed from the blood by the kidney and passed out in the urine.
The scanner is a large tube-like machine. The tube generates the magnetic field needed for imaging. You will be taken to the imaging room and asked to lie on a table that can slide in or out of the scanner. You may need to go head-first or feet-first depending on the part of your body that is being scanned. Generally the part of your body to be examined will be placed in the middle of the tube. The tube is open ended and for many scans your head will remain outside the tube.
A radiographer operates the scanner from behind a window, and will be able to see and hear you during the procedure. It can take several minutes for each picture to be taken, and it’s important to lie very still and breathe gently during the process.
The machine will make quite a loud knocking or buzzing sound so it may help to wear earplugs. You will be fitted with earphones which play music and allow the radiographer to speak to you.
When the scan is complete, the table will be moved back out from the scanner and your radiographer will help you get down from the table.
An MRI scan is a commonly performed and generally safe procedure. Complications from an MRI scan test are very uncommon and most people are not affected.
In rare cases, it’s possible to have an allergic reaction to the contrast injection which is used in some studies. Medicines are available to treat any allergic reaction.
Most people do not mind having part of their body in a MRI scanner. But if you feel at all worried about this, please tell your doctor or radiographer. The new 3T MRI scanner at the Hospital of St John and St Elizabeth has more space around your body the previous generation of scanners.
Your doctor will explain the benefits and risks of having an MRI scan and will also discuss alternatives to the procedure.