MRI produces highly detailed images of various body parts without the use of x-rays. It can be 2 or 3 dimensional and can look like “slices” in different directions through the body part under examination. It is better to “zoom” into a specific area rather than to do the whole body (although this can be done), this way much better images can be obtained, and even small changes, injuries or abnormalities can be detected.
MRI does not use x-rays and the radio waves used in MRI are not known to be harmful.
MRI can lead to the early detection and treatment of disease.
The MRI images are extremely precise and can often give as much information as looking at the tissue itself. Therefore it has got the potential to reduce the munber of diagnostic tests and examinations.
Our bodies are composed of tiny little particles called atoms. The atom has a central nucleus and orbiting electrons. The nucleus contains nucleons, subdivided into protons (positively charged), neutrons (no charge) and electrons (negatively charged).
Under normal circumstances these protons inside of the atoms spin randomly. The MRI relies on the spinning motion of specific nuclei present in biological tissues. These nuclei are known as MRI active nuclei.
Motion within the atom:
Our MRI magnet is a very strong superconductive magnet that is always on. It is much stronger (thousands of times) stronger than the earth’s surface magnetic field.
It causes most of the protons to line up together in the direction of the magnetic field and spin in the same direction.
An RF signal is then applied at 90° to the magnetic field at the same precessional frequency of the hydrogen (water) protons. Hydrogen is used because it is abundant in the body. It is the “H” in H²O.
This RF signal causes the protons to move out of alignment and when the signal is stoped they move back into alignment. This process releases energy.
The MRI machine is located within a specially shielded room to avoid outside interference, caused by the use of radio waves of ordinary FM radio stations.
There is a specific coil for each region that we scan. These coils measure the energy released by the protons that were disturbed by the RF signal. It also measures the time that it takes for the protons to return to their aligned positions.
The computer uses all the information to reconstruct images on a computer screen. These images can then be manipulated in different directions and copied onto films, CD’s or DVD’s for a permanent record.
It is very valuable to help diagnose:
Just relax and go about your normal routine unless otherwise specified. Bring something to read or do while you wait for your scan.
For all pelvis and abdomen scans we ask the patient to fast for 6 hours prior to the scan to stop bowel movement in order to get a “still” scan. These scans include: general pelvis, uterus, endometrium, prostate, bladder, kidneys, small bowel, liver and the gallbladder and bile system (MRCP). It is not necessary to fast for other MRI examinations.
If you are having a liver scan delayed imaging is also necessary and another appointment of 10 minutes will be booked on the same day about 90 minutes after the firts appointment. You can eat and drink as normal after the first appointment.
Please let us know if you are diabetic and then bring something to eat for after the examination.
Take any medication as normal.
You will be given a form or several forms to fill out before your procedure. This is to obtain your medical history and to see whether you are safe to go into the MRI scanner. Some of the questions would have been ask already when we made the appointment, but you still have to fill out the appropriate forms and will be asked some of the questions again before you go into the scanner.
The scanning procedure will be explained to you and you may ask questions at the time.
You will have to remove any metal objects, such as jewellery, hearing aids any piercing, hairpins, glasses, wigs with metal clips, dentures with metal or a denture plate if it is not permanent. Some people might like to remove some of these items at home to save time.
Some make-up can also cause problems for the MRI scan e.g. some mascaras can contain metal fragments that can cause artefacts and it is best not to wear any and it you have any questions or are uncertain then please let us know.
We will also change you into a hospital gown, because metal buttons, bra clips zippers etc. will also create problems.
The technologist will help you onto the scan table and you will be positioned as comfortable as possible. Depending on the scan you will go in head or feet first into the scanner.
The scanner makes a lot of noise and you will be given earplugs or earmuffs before the scan starts.
You can talk to the radiographer during your procedure if needed, but while the scanner is scanning it might be hard to hear, so an alarm bell will be given to you before the scan starts to alert the radiographer should anything be the matter. She will then pause the scan and talk to you.
You will be asked to lie very still and not to move at all as this would result in “blurry” and unclear images. Let the Radiographer know in case you need to cough then she can pause the scan and continue.
Claustrophobia can also be a problem for some patients. If someone is very anxious a sedative might be given. It is important to let the MRI department know beforehand so that you can be booked in an appropriate session for this. You need to bring a “driver’ with you for this appointment as you are not allowed to drive or operate heavy machinery for 24 hours after the sedation.
Try to relax as much as possible and keep still! The machine might look intimidating, but there is nothing to worry about. The radiographers are just an alarm bell away and you will not feel anything!
The radiographer will do the first scan that will only take a few seconds and will talk to you after that to see whether you are ok.
She will then continue with the scan.
You will hear very loud noises coming from the machine. They are all different and there will be thumping and grinding noises when the radio waves are turned on an off and also some grating and other machine like noises.
If you have any more questions or are uncertain about anything regarding your MRI procedure, please no not hesitate to ring us.
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