MMRI, or magnetic resonance imaging, is a means of “seeing” inside of the body in order for doctors to find certain diseases or abnormal conditions. MRI does not rely on the type of radiation (i.e. ionizing radiation) used for an x-ray or computed tomography (CT) scan. The MRI examination requires specialized equipment using a powerful, constant magnetic field, rapidly changing local magnetic fields, radiofrequency energy and dedicated equipment including a powerful computer to create very clear pictures of internal body structures.
During the MRI examination the patient is placed within the MRI system or “scanner”. The powerful, constant magnetic field aligns a tiny fraction of subatomic particles called protons that are present in most of the body’s tissues. Radiofrequency energy is applied to cause these protons to produce signals that are picked up by a receiver within the scanner. The signals are specially characterized using the rapidly changing, local magnetic field and then computer-processed to produce images of the body part of interest.
What is MRI used for ?
MRI has become the preferred procedure for diagnosing a large number of potential problems in many different parts of the body. In general MRI creates pictures that can show differences between normal and abnormal tissue. Doctors and specialists use MRI to examine the brain, spine, joints (e.g., knee, shoulder, wrist, and ankle), abdomen, pelvic region, breast, blood vessels, heart and other body parts.
How safe is MRI ?
The powerful magnetic field of the scanner can attract certain metallic objects known as “ferromagnetic” objects, causing them to move suddenly and with great force towards the center of the MRI system. This may pose a risk to the patient or anyone in the way of the object. Therefore, great care is taken to prevent ferromagnetic objects from entering the MRI system room. It is vital that you remove metallic objects in advance of an MRI exam including watches, jewelry and items of clothing that have metallic threads or fasteners.
MRI facilities have screening procedures that, when carefully followed, will ensure that the MRI technologist and radiologist knows about the presence of metallic implants and materials so that special precautions can be taken (see below). In some unusual cases the examination may be canceled because of concern related to a particular implant or device. For example if an MRI is ordered, it may be cancelled if the patient has a ferromagnetic aneurysm clip because of the risk dislodging the clip from the blood vessel. Also, the magnetic field of the scanner can damage an external hearing aid or cause a heart pacemaker to malfunction. If you have a bullet or other metallic fragment in your body there is a potential risk that it could change position possibly causing injury.
How you can prepare for the MRI examination?
There’s no special preparation necessary for the MRI examination. Unless your doctor specifically requests that you not eat or drink anything before the exam, there are no food or drink restrictions. Continue to take any medication prescribed by your doctor unless otherwise directed.
You won’t be allowed to wear anything metallic during the MRI examination so it would be best to leave watches, jewelry or anything made from metal at home. Even some cosmetics contain small amounts of metals so it is best to not wear make-up.
In order to prevent metallic objects from being attracted by the powerful magnet of the MR system you will typically receive a gown to wear during your examination. Items that need to be removed by patients before entering the MRI system room include:
• Purse, wallet, money clip, credit cards, cards with magnetic strips
• Electronic devices such as beepers or cell phones
• Hearing aids
• Metal jewelry, watches
• Pens, paper clips, keys, coins
• Hair barrettes, hairpins
• Any article of clothing that has a metal zipper, buttons, snaps, hooks, underwires, or metal threads
• Shoes, belt buckles, safety pins.
Before the MRI procedure, you will be asked to fill out a screening form asking about anything that might create a health risk or interfere with imaging. You will also undergo an interview by a member of the MRI facility to ensure that you understand the questions on the form. Even if you have undergone an MRI procedure in the past, you will still be asked to complete an MRI screening form.
Examples of items or things that may create a health hazard or other problem during an MRI exam include:
• Implantable cardioverter defibrillator (ICD)
• Aneurysm clip
• Metal implant
• Implanted drug infusion device
• Foreign metal objects, especially if in or near the eye
• Shrapnel or bullet wounds
• Permanent cosmetics or tattoos
• Dentures/teeth with magnetic keepers
• Other implants that involve magnets
• Medication patch (i.e. transdermal patch) that contains metal foil.
Discuss with the MRI technologist or radiologist at the MRI center if you have questions or concerns about any implanted object or health condition that could impact the MRI procedure. This is particularly important if you have undergone surgery involving the brain, ear, eye, heart, or blood vessels.
Important Note: If you are pregnant or think that you could be pregnant you must notify your physician and the radiologist or the MRI technologist at Global Hawk Imaging and Diagnostics prior to the MRI procedure.
Before entering the MRI system room a friend or relative that might be allowed to accompany you will be asked questions to ensure that he or she may safely enter the MRI system room and will likewise be instructed to remove all metallic objects. Additionally this individual will need to fill out a screening form
Open MRI at GHID
There are three main types of MRI scanning machines – closed-bore, open and wide bore MRI. The closed-bore MRI has a circular tube which the patient enters and the diameter is generally 0.6 metres. Many patients even those who are not claustrophobic have difficulty getting comfortable in such a small space. This makes it difficult to carry out the MRI scan and difficult to maintain absolute stillness which is necessary for accurate imaging. The wide-bore MRI scanning system is still closed but has a slightly wider diameter than the closed-bore MRI system of 0.7 metres. For some patients even this increase in diameter is enough to allow themselves to go through with the MRI scan but for many it is still too narrow and they refuse the procedure.
At Global Hawk Imaging and Diagnostics we use the Neusoft open MRI system which is open at both sides leaving space for the patient as they are not enclosed in a narrow circular tube. This allows for a much more comfortable experience where they can maintain stillness easily allowing for excellent clarity of images of the affected area. The noise is also reduced and less severe than the wide-bore and closed MRI systems. Global Hawk Imaging and Diagnostics Neusoft MRI system achieves the perfect balance of imaging need and patient comfort.