MRI is noninvasive and does not use ionizing radiation that helps physicians diagnose and treat medical conditions.
Magnetic resonance imaging (MRI) uses a powerful magnetic field, radio waves and a computer to produce detailed pictures of the body's internal structures that are clearer, more detailed and more likely in some instances to identify and accurately characterize disease than other imaging methods.
It is used to evaluate the body for a variety of conditions, including tumors and diseases of the liver, heart, and bowel. It may also be used to monitor an unborn child in the womb.
Why should I do it ?
- MRI is usually the best choice for examining the body's major joints like the knee.
The examination is typically performed to diagnose or evaluate:
- Knee pain, weakness, swelling or bleeding in the tissues in and around the joint
- Damaged cartilage, meniscus, ligaments or tendons
- Sports-related knee injuries, such as sprains and torn ligaments, cartilage, or tendons
- Bone fractures that may not be visible on x-rays and other imaging tests
- Damage from arthritis
- Build-up of fluid in the knee joint
- Infections (such as osteomyelitis)
- Tumors (primary tumors and metastases) involving bones and joints
- Dead bone
- A feeling that your knee is giving away at the joint
- Decreased motion of the knee joint
- Knee cap injury or pain
- Complications related to implanted surgical devices
- Pain or trauma following knee surgery
- Your doctor may also order an MRI to determine if knee arthroscopy or another surgical procedure is needed, and to monitor your progress after knee surgery.
Any preparations needed?
- You may need to wear a gown, or you may be allowed to wear your own clothing if it is loose-fitting and has no metal fasteners.
Guidelines about eating and drinking before an MRI vary between specific exams and facilities. Unless you are told otherwise, take food and medications as usual.
- Tell the technologist or radiologist if you have any serious health problems or recently had surgery.
- If you have claustrophobia (fear of enclosed spaces) or anxiety, you may want to ask your doctor to prescribe a mild sedative prior to your exam.
Leave all jewelry and other accessories at home or remove them prior to the MRI scan. Metal and electronic items can interfere with the magnetic field of the MRI unit, and they are not allowed in the exam room. They may cause burns or become harmful projectiles within the MRI scanner room. These items include:
- jewelry, watches, credit cards and hearing aids, all of which can be damaged
- pins, hairpins, metal zippers and similar metallic items, which can distort MRI images.
- removable dental work
- pens, pocket knives and eyeglasses
- body piercings
- Mobile phones, electronic watches and tracking devices.
- Do not prepare food for others that requires prolonged handling with bare hands.
In most cases, an MRI exam is safe for patients with metal implants, except for a few types. People with the following implants may not be scanned and should not enter the MRI scanning area without first being evaluated for safety:
- some cochlear (ear) implants
- some types of clips used for brain aneurysms
- some types of metal coils placed within blood vessels
- some older cardiac defibrillators and pacemakers
Tell the technologist if you have medical or electronic devices in your body. These devices may interfere with the exam or pose a risk. Many implanted devices will have a pamphlet explaining the MRI risks for that particular device. If you have the pamphlet, bring it to the attention of the scheduler before the exam. MRI cannot be performed without confirmation and documentation of the type of implant and MRI compatibility. You should also bring any pamphlet to your exam in case the
- Tell the technologist or radiologist about any shrapnel, bullets, or other metal that may be in your body. Foreign bodies near and especially lodged in the eyes are very important because they may move or heat up during the scan and cause blindness. Dyes used in tattoos may contain iron and could heat up during an MRI scan. This is rare. Tooth fillings, braces, eyeshadows and other cosmetics usually are not affected by the magnetic field. However, they may distort images of the facial area or brain. Tell the radiologist about them.