MRI scans produce clear, black-and-white pictures of the inside of your body. They can spot problems that aren’t seen as well by X-ray or CT scans.
You’ll be asked to change into a gown and to leave any metal objects at the front desk. You’ll be given a buzzer to press if you need help during the exam.
What is an MRI?
An MRI is a test that uses a powerful magnet and radio waves to produce detailed pictures of the inside of your body. It is painless and does not require X-rays or other radiation. You will be asked to remove any metal objects from your body before the scan, such as wristwatches, keys and jewellery. You will also be told not to eat or drink anything for 4 to 6 hours before the exam.
You will be asked to lie down on a table that slides into the opening of the scanner, which looks like a long narrow tube. The technologist who operates the machine will watch you from a room that is separate from the scanner. They will talk with you through an intercom and can hear and see you at all times. They will also ask you questions about your medical history and any allergies to contrast dye. They will also ask whether you have a condition called claustrophobia (fear of enclosed spaces). If you do, you may be prescribed a sedative before the exam to help relieve your fear.
If you are having an MRI with contrast, the technician will inject a special dye into a vein (IV) in your hand or arm before the procedure starts. The dye helps the radiologist see certain areas more clearly. The injection might cause itching and a slight allergic reaction, which is rare but important to tell the technician about.
The strong magnetic field used in an MRI can cause heating or movement of some implanted electronic devices, such as cardiac pacemakers and defibrillators. It can also affect some types of surgical clips used to treat brain aneurysms and metal coils placed in blood vessels and around some cardiac pacemakers.
You should tell the radiologist and/or technologists about any metal objects in or on your body, such as shrapnel or bullets. Also let them know if you have tattoos, as the dyes used in some of them contain iron and can heat up during an MRI scan. You should also tell them if you have any metal in or near your eyes, as this could move or become lodged in them during the scan.
How does an MRI work?
A large magnet, radio waves and a computer are used to produce detailed pictures of body parts. Unlike CT scanning, which uses radiation, an MRI is safe for patients of any age.
The patient will be pushed into a tube-like machine, with openings on both sides of the scanner. The magnet is very large, but it is also surrounded by a circular opening that allows air to circulate freely throughout the scan. The patient must lie very still during the scan, as any movement can cause distortion. Depending on the area being scanned, you may be asked to hold your breath for several seconds.
People who are claustrophobic (afraid of enclosed spaces) may find an MRI stressful, but medication is available to help reduce anxiety. Individuals who are uncomfortable in close spaces should tell their health care provider, as they may be able to choose an open MRI scan that is less stressful.
When the patient enters the scanner, they will be asked to change into a gown and to remove any metal objects, such as jewelry, watches, credit cards or hearing aids. Metal can damage the MRI machine or cause a distortion of the images. A person who is unable to remove these items will be allowed to have an MRI scan only if the physician has determined that the potential risks outweigh the benefit of having the exam.
During the exam, a radiographer will monitor the patient from another room. The patient will be given a headset to wear for the duration of the scan and a squeeze ball to press if they want to signal the radiographer for assistance. During the scan, the radiographer will hear loud tapping noises, which are caused by the magnetic fields changing and the electric current in the scanner coils being turned on and off. These sounds can be uncomfortable and are why the earplugs are provided.
A radiologist, a doctor who specializes in medical images, will analyze the results and send them to the health care provider who ordered the MRI. The results are usually available in one to two weeks.
What are the benefits of an MRI?
The pictures produced by MRI, like an MRI at Biomed Scan, are more detailed and clearer than those of CT scans. They allow doctors to see soft tissues and organs more clearly, so they can diagnose a variety of conditions. In addition, MRI does not use radiation, so it is more comfortable for patients than other types of scans. However, the loud clanging noises created during the scan can be distressing to some people. Earplugs or headphones can be provided to reduce the noise. Some patients choose to listen to music to help them relax. Others may be given a squeeze ball to hold, which they can use to signal the technician at any time if they feel uncomfortable. The scan can take a while, and you will need to remain still at all times. Some patients are given a sedative during their scan to help them stay calm and relaxed. If you are given a sedative, you will need to arrange for someone to drive you home after the test, as you will not be able to drive until 24 hours afterwards.
An MRI scanner looks like a short tube that is open on both ends. You lie down on a motorised bed that slides into the opening of the machine. The radiographer who runs the scanner will be in another room, watching you from a monitor. The radiographer can communicate with you via an intercom. If you have a fear of enclosed spaces (claustrophobia), you may be offered a drug to make you more comfortable during the test.
Some MRI scans require the injection of a dye to help doctors see certain areas more clearly. The dye will be given through a vein in your arm or hand. Other exams can be completed with small devices called coils that are placed around the part of your body being scanned. These coils send and receive the radio waves that create the images.
Some MRI exams can be very long, up to 60 minutes or more. You will need to lie still during this time, as movement will distort the pictures. The MRI does not cause any pain, although some patients can feel uncomfortable lying in the same position for so long.
What are the risks of an MRI?
MRI is generally safe and poses no risk for most people when appropriate safety guidelines are followed. However, there are certain conditions that may make it unsuitable for you to receive an MRI. You cannot have an MRI if you have any metal in or on your body, such as artificial joints or stents, surgical screws or aneurysm clips, pacemakers and other implanted devices or some types of jewelry. The ferromagnetic objects can cause magnetic pull that could damage the equipment or even harm you. Some patients experience burns from contact with the bore of the scanner and others have problems with implanted or accessory medical devices that can interfere with the images, such as a heart rhythm device, an insulin pump or an external insulin pump.
In addition to avoiding any metal objects, you will be asked to remove any jewelry or other personal items before the exam. You will also be given a buzzer to press when the radiographer is ready to begin the scan, so you can communicate with them. You will be given earplugs or headphones to help reduce the noise of the scanner and you should be prepared to hold very still during the scan. This is difficult for some people, particularly if they are claustrophobic (fear of closed spaces). In some cases, a doctor may prescribe a mild sedative to relax you before the MRI scan.
You can expect to hear tapping or thumping sounds during the scan and this is normal, as it is part of the machine creating the energy to take the images. The thumping sounds can be distracting and uncomfortable, but it is important to stay still so the images are clear.
Some patients with a condition called ascites (a build-up of fluid in the abdomen or pelvis) can develop artifacts that distort the image quality. In these cases, your doctor can use another type of scan, such as CT or X-ray to help determine the cause.
You may be injected with a contrast dye, such as gadolinium, to enhance the visibility of certain tissues and blood vessels. This is typically only used in some types of MRI scans. You should inform your doctor if you are allergic to the injection.
