Magnetic resonance imaging (MRI) uses a large magnet and radio waves to look at organs and structures inside your body. Health care professionals use MRI scans to diagnose a variety of conditions, from torn ligaments to tumors. MRIs are very useful for examining the brain and spinal cord.

During the scan, you lie on a table that slides inside a tunnel-shaped machine. Doing the scan can take a long time, and you must stay still. The scan is painless. The MRI machine makes a lot of noise. The technician may offer you earplugs.

Before you get a scan, tell your doctor if you :

• Are pregnant
• Have pieces of metal in your body. You might have metal in your body if you have a shrapnel or bullet injury or if you are a welder.
• Have metal or electronic devices in your body, such as a cardiac pacemaker or a metal artificial joint

Magnetic Resonance Imaging (MRI) is a non-invasive imaging technology that produces three dimensional detailed anatomical images. It is often used for disease detection, diagnosis, and treatment monitoring. It is based on sophisticated technology that excites and detects the change in the direction of the rotational axis of protons found in the water that makes up living tissues.

MRIs employ powerful magnets which produce a strong magnetic field that forces protons in the body to align with that field. When a radiofrequency current is then pulsed through the patient, the protons are stimulated, and spin out of equilibrium, straining against the pull of the magnetic field. When the radiofrequency field is turned off, the MRI sensors are able to detect the energy released as the protons realign with the magnetic field. The time it takes for the protons to realign with the magnetic field, as well as the amount of energy released, changes depending on the environment and the chemical nature of the molecules. Physicians are able to tell the difference between various types of tissues based on these magnetic properties.

To obtain an MRI image, a patient is placed inside a large magnet and must remain very still during the imaging process in order not to blur the image. Contrast agents (often containing the element Gadolinium) may be given to a patient intravenously before or during the MRI to increase the speed at which protons realign with the magnetic field. The faster the protons realign, the brighter the image.

Gadolinium-Based Contrast Agents (GBCA) are intravenous drugs used in diagnostic imaging procedures to enhance the quality of magnetic resonance imaging (MRI) or magnetic resonance angiography (MRA).

Magnetic Resonance Imaging (MRI) is a medical imaging procedure for making images of the internal structures of the body. MRI scanners use strong magnetic fields and radio waves (radiofrequency energy) to make images. The signal in an MR image comes mainly from the protons in fat and water molecules in the body.

During an MRI exam, an electric current is passed through coiled wires to create a temporary magnetic field in a patient’s body. Radio waves are sent from and received by a transmitter/receiver in the machine, and these signals are used to make digital images of the scanned area of the body. A typical MRI scan last from 20 - 90 minutes, depending on the part of the body being imaged.

For some MRI exams, intravenous (IV) drugs, such as gadolinium-based contrast agents (GBCAs) are used to change the contrast of the MR image. Gadolinium-based contrast agents are rare earth metals that are usually given through an IV in the arm.

MRI scanners are particularly well suited to image the non-bony parts or soft tissues of the body. They differ from computed tomography (CT), in that they do not use the damaging ionizing radiation of x-rays. The brain, spinal cord and nerves, as well as muscles, ligaments, and tendons are seen much more clearly with MRI than with regular x-rays and CT; for this reason MRI is often used to image knee and shoulder injuries.

In the brain, MRI can differentiate between white matter and grey matter and can also be used to diagnose aneurysms and tumors. Because MRI does not use x-rays or other radiation, it is the imaging modality of choice when frequent imaging is required for diagnosis or therapy, especially in the brain. However, MRI is more expensive than x-ray imaging or CT scanning.

One kind of specialized MRI is functional Magnetic Resonance Imaging (fMRI.) This is used to observe brain structures and determine which areas of the brain “activate” (consume more oxygen) during various cognitive tasks. It is used to advance the understanding of brain organization and offers a potential new standard for assessing neurological status and neurosurgical risk.

An MRI scanner can be used to take images of any part of the body (e.g., head, joints, abdomen, legs, etc.), in any imaging direction. MRI provides better soft tissue contrast than CT and can differentiate better between fat, water, muscle, and other soft tissue than CT (CT is usually better at imaging bones). These images provide information to physicians and can be useful in diagnosing a wide variety of diseases and conditions.

MRI gives health care providers useful information about a variety of conditions and diagnostic procedures including:

• abnormalities of the brain and spinal cord
• abnormalities in various parts of the body such as breast, prostate, and liver
• injuries or abnormalities of the joints
• the structure and function of the heart (cardiac imaging)
• areas of activation within the brain (functional MRI or fMRI)
• blood flow through blood vessels and arteries (angiography)
• the chemical composition of tissues (spectroscopy)

In addition to these diagnostic uses, MRI may also be used to guide certain interventional procedures.

^{Although MRI does not emit the ionizing radiation that is found in x-ray and CT imaging, it does employ a strong magnetic field. The magnetic field extends beyond the machine and exerts very powerful forces on objects of iron, some steels, and other magnetizable objects; it is strong enough to fling a wheelchair across the room. Patients should notify their physicians of any form of medical or implant prior to an MR scan.}

When having an MRI scan, the following should be taken into consideration:

• People with implants, particularly those containing iron, — pacemakers, vagus nerve stimulators, implantable cardioverter- defibrillators, loop recorders, insulin pumps, cochlear implants, deep brain stimulators, and capsules from capsule endoscopy should not enter an MRI machine.
• Noise—loud noise commonly referred to as clicking and beeping, as well as sound intensity up to 120 decibels in certain MR scanners, may require special ear protection.
• Nerve Stimulation—a twitching sensation sometimes results from the rapidly switched fields in the MRI.
• Contrast agents—patients with severe renal failure who require dialysis may risk a rare but serious illness called nephrogenic systemic fibrosis that may be linked to the use of certain gadolinium-containing agents, such as gadodiamide and others. Although a causal link has not been established, current guidelines in the United States recommend that dialysis patients should only receive gadolinium agents when essential, and that dialysis should be performed as soon as possible after the scan to remove the agent from the body promptly.
• Pregnancy—while no effects have been demonstrated on the fetus, it is recommended that MRI scans be avoided as a precaution especially in the first trimester of pregnancy when the fetus’ organs are being formed and contrast agents, if used, could enter the fetal bloodstream.

• Claustrophobia—people with even mild claustrophobia may find it difficult to tolerate long scan times inside the machine. Familiarization with the machine and process, as well as visualization techniques, sedation, and anesthesia provide patients with mechanisms to overcome their discomfort. Additional coping mechanisms include listening to music or watching a video or movie, closing or covering the eyes, and holding a panic button. The open MRI is a machine that is open on the sides rather than a tube closed at one end, so it does not fully surround the patient. It was developed to accommodate the needs of patients who are uncomfortable with the narrow tunnel and noises of the traditional MRI and for patients whose size or weight make the traditional MRI impractical. Newer open MRI technology provides high quality images for many but not all types of examinations.

Adverse events for MRI scans are very rare. Millions of MRI scans are performed in the US every year, and the FDA receives around 300 adverse event reports for MRI scanners and coils each year from manufacturers, distributors, user facilities, and patients. The majority of these reports describe heating and/or burns (thermal injuries). Second degree burns are the most commonly reported patient problem. Other reported problems include injuries from projectile events (objects being drawn toward the MRI scanner), crushed and pinched fingers from the patient table, patient falls, and hearing loss or a ringing in the ear (tinnitus). The FDA has also received reports concerning the inadequate display or quality of the MR images.

The MR environment presents unique safety hazards for patients with implants, external devices and accessory medical devices. Examples of implanted devices include artificial joints, stents, cochlear implants, and pacemakers. An external device is a device that may touch the patient like an external insulin pump, a leg brace, or a wound dressing. An accessory device is a non-implanted medical device (such as a ventilator, patient monitor) that is used to monitor or support the patient.

• The strong, static magnetic field of the MRI scanner will pull on magnetic materials and may cause unwanted movement of the medical device.
• The radiofrequency energy and magnetic fields that change with time may cause heating of the implanted medical device and the surrounding tissue, which could lead to burns.
• The magnetic fields and radiofrequency energy produced by an MRI scanner may also cause electrically active medical devices to malfunction, which can result in a failure of the device to deliver the intended therapy.
• The presence of the medical device will degrade the quality of the MR image, which may make the MRI scan uninformative or may lead to an inaccurate clinical diagnosis, potentially resulting in inappropriate medical treatment.

Therefore patients with implanted medical devices should not receive an MRI exam unless the implanted medical device has been positively identified as MR Safe or MR Conditional. An MR Safe device is nonmagnetic, contains no metal, does not conduct electricity and poses no known hazards in all MR environments. An MR Conditional device may be used safely only within an MR environment that matches its conditions of safe use. Any device with an unknown MRI safety status should be assumed to be MR Unsafe.

Before your MRI exam, you will likely be asked to fill out a screening questionnaire. The International Society for Magnetic Resonance in Medicine (ISMRM) has a sample patient screening form available on its website. For your safety, answering the questionnaire accurately is extremely important. In particular, make sure you notify the MRI technologist or radiologist if you have any implanted medical devices, such as stents, knee or hip replacements, pacemakers, or drug pumps. Also be sure to tell the technologist if you have any tattoos or drug patches as these can cause skin irritation or burns during the exam. The medical team will need to make sure that these devices can safely enter the MR environment.

Some devices are MR Safe or MR Conditional, meaning that they can be safely used in the MR environment under specific conditions. If you have an implant card for your device, bring it with you to your MRI exam so that you can help the doctor or the MRI technologist identify what type of device you have.

The space where you will lay in an MRI scanner to have your images taken can be a tight fit for some people, especially larger individuals. If you believe that you will feel claustrophobic, tell the MRI technologist or your doctor.

The MRI scanner will make a lot of noise as it takes images. This is normal. You should be offered earplugs and/or headphones to make the noise sound less loud. You may also be able to listen to music through the headphones to make the MRI exam more enjoyable.

If your exam includes a contrast agent, the MRI technologist will place a small intravenous (IV) line in one of your arms. You may feel some coldness when the contrast agent is injected. Be sure to notify the technologist if you feel any pain or discomfort.

Remember, your doctor has referred you to have an MRI because he or she believes the scan will provide useful information. If you have any questions about your procedure, don’t be afraid to ask.

Questions to ask your doctor

• “What information will the MRI scan provide? How might this change my treatment options?”
• “Is there any reason why I shouldn’t have an MRI scan?” (If you have any implanted devices (such as a pacemaker, stents, an insulin pump, or an artificial joint), be sure your doctor knows about them.)
• “Will my exam involve contrast agent? What additional information will using the contrast agent provide?”

Questions to ask the MRI technologist

• “How long can I expect my scan to last?”
• “Can I listen to music during my MRI scan? Can I choose the music?”
• “Where is the call button I can use to let you know if there is a problem?”

Non-invasive diagnostic technique for visualizing the PANCREATIC DUCTS and BILE DUCTS without the use of injected CONTRAST MEDIA or x-ray. MRI scans provide excellent sensitivity for duct dilatation, biliary stricture, and intraductal abnormalities.