- Magnetic Resonance Imaging (MRI) Safety
- What Is MRI Scan? Uses, Safety, and Side Effects
- What is an MRI (magnetic resonance imaging)?
- What are the uses for an MRI?
- What are the risks and side effecs of an MRI?
- How do I prepare for an MRI? How is it performed?
- When do I receive the results of an MRI?
- What does an MRI look (pictures)?
- What new MRI scanners available?
- MRI scan
- What Is a MRI? What Happens When I Get One?
- MRI Scans: Definition, uses, and procedure
- Functional magnetic resonance imaging (fMRI)
- I have braces or filings, should I still undergo the scan?
- Can I move while I am in the MRI tunnel?
- I am claustrophobic, what can I do?
- Do I need an injection of contrast before my MRI scan?
- Can I have an MRI scan if I am pregnant?
Magnetic Resonance Imaging (MRI) Safety
Magnetic resonance imaging, or MRI, is a way of obtaining detailed images of organs and tissues throughout the body without the need for x-rays or “ionizing” radiation. Instead, MRI uses a powerful magnetic field, radio waves, rapidly changing magnetic fields, and a computer to create images that show whether or not there is an injury, disease process, or abnormal condition present.
For the MRI exam, the patient is placed inside of the MR system or scanner—typically a large donut-shaped device that is open on both ends. The powerful magnetic field aligns atomic particles called protons that exist in most body tissues.
The applied radio waves then interact with these protons to produce signals that are picked up by a receiver within the MR scanner. The signals are specially characterized using the rapidly changing magnetic field.
With the help of computer processing, images of tissues are created as “slices” that can be viewed in any orientation.
An MRI examination causes no pain, and the electromagnetic fields produce no known tissue damage of any kind. The MR scanner may make loud tapping, knocking, or other noises at times during the procedure.
Earplugs are provided to prevent problems that may be associated with this noise.
At all times, you will be monitored and you will be able to communicate with the MRI technologist or the MR scanner operator using an intercom system or by other means.
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MRI is the preferred procedure for diagnosing a large number of potential problems or abnormal conditions that may affect different parts of the body.
In general, MRI creates pictures that can show differences between healthy and unhealthy or abnormal tissues. Physicians use MRI to examine the brain, spine, joints (e.g.
, knee, shoulder, hip, wrist, and ankle), abdomen, pelvic region, breast, blood vessels, heart and other body parts.
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The powerful magnetic field of the MR system can attract objects made from certain metals (i.e., known as ferromagnetic) and cause them to move suddenly and with great force. This can pose a possible risk to the patient or anyone in the object's “flight path.
” Therefore, great care is taken to be certain that external objects such as ferromagnetic screwdrivers and oxygen tanks are not brought into the MR system area.
As a patient, it is vital that you remove all metallic belongings in advance of an MRI exam, including external hearing aids, watches, jewelry, cell phones, and items of clothing that have metallic threads or fasteners.
Additionally, makeup, nail polish, or other cosmetics that may contain metallic particles should be removed if applied to the area of the body undergoing the MRI examination.
The powerful magnetic field of the MR system will pull on any iron-containing object in the body such as a medical implant, certain aneurysm clips or certain medication pumps. Every MRI facility has a comprehensive screening procedure and protocols.
When carefully followed, these steps ensure that the MRI technologist and radiologist know about the presence of any metallic implants and materials in the patient. Special precautions can usually be taken. In some unusual cases, due to the presence of an unacceptable implant or device, the exam may have to be canceled.
For example, the MRI exam will not be performed if a ferromagnetic aneurysm clip is present because there is a risk of the clip moving and causing serious harm to the patient. In some cases, certain medical implants can heat substantially during the MRI exam as a result of the radiofrequency energy that is used for the procedure.
This heating may result in an injury to the patient. Therefore, it is very important to inform the MRI technologist about any implant or other internal object that you may have prior to entering the MR scanner room.
The powerful magnetic field of the MR system may damage an external hearing aid or cause a heart pacemaker, electrical stimulator, or neurostimulator to malfunction or cause injury. If you have a bullet or any other metallic fragment in your body there is a potential risk that it could change position and possibly cause an injury.
In addition, a metallic implant or other object may cause signal loss or alter the MR images making it difficult for the radiologist to see the images correctly. This may be unavoidable, but if the radiologist knows about it, allowances can be made when obtaining and interpreting the MR images.
For some MRI exams, a contrast material known as a gadolinium contrast agent may be injected into a vein to help improve the information seen on the MR images. Un the contrast materials used in x-ray exams or computed tomography (CT) scans, a gadolinium contrast agent does not contain iodine and, therefore, rarely causes an allergic reaction or other problem.
However, if you have a history of kidney disease, kidney failure, kidney transplant, liver disease, or other conditions, you must inform the MRI technologist and/or radiologist before receiving a gadolinium contrast agent.
If you are unsure about the presence of these conditions, please discuss these matters with the MRI technologist or radiologist prior to the MRI examination
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You will typically receive a gown to wear during your MRI examination. Before entering the MR system room, you will be asked a variety of questions (i.e., using a special screening form) including if you have implants or devices.
Next, you will be instructed to remove all metallic objects from pockets and hair, as well as metallic jewelry. Additionally, any individual that will be going with you in the MRI scanner room will be required to follow these same instructions and procedures including filling out the same forms.
If you have questions or concerns, please discuss them with the MRI technologist or radiologist prior to the MRI examination.
As previously indicated, you will be asked to fill out a screening form asking about anything that might create a health risk or interfere with the MRI exam. Items that may create a health hazard or other problem during an MRI include:
- Certain cardiac pacemakers or implantable cardioverter defibrillators (ICDs)
- Ferromagnetic metallic vascular clips placed to prevent bleeding from intracranial aneurysms or blood vessels
- Some external or implanted medication pumps (such as those used to deliver insulin, pain-relieving drugs, or chemotherapy)
- Certain cochlear (i.e., for hearing) implants
- Certain neurostimulation systems
- Catheters that have metallic components
- A bullet, shrapnel or other type of metallic fragment
- A metallic foreign body located within or near the eye (such an object generally can be seen on an x-ray; metal workers are most ly to have this problem)
Important note: Some items, including certain cardiac pacemakers, ICDs, neurostimulation systems, cochlear implants, and medication pumps are acceptable for MRI.
However, the MRI technologist and radiologist must know the exact type that you have in order to follow special procedures to ensure your safety.
Therefore, in order to help with the pre-MRI screening procedure, it is important for you to obtain information about any implant that you may have and to provide it to the MRI technologist.
Items that need to be removed by patients and individuals before entering the MR system room include:
- Purse, wallet, money clip, credit cards, cards with magnetic strips
- Electronic devices such as beepers, cell phones, smartphones and tablets
- Hearing aids
- Metallic jewelry and watches
- Pens, paper clips, keys, coins
- Hair barrettes, hairpins, hair clips and some hair ointments
- Shoes, belt buckles, safety pins
- Any article of clothing that has metallic fibers or threads, metallic zippers, buttons, snaps, hooks, or underwire
Objects that may interfere with image quality if close to the area being scanned include:
- Metallic spinal rod
- Plates, pins, screws, or metal mesh used to repair a bone or joint
- Joint replacement or prosthesis
- Metallic jewelry including those used for body piercing or body modification
- Some tattoos or tattooed eyeliner (these alter MR images, and there is a chance of skin irritation or swelling; black and blue pigments are the most troublesome)
- Makeup (such as eye shadow and eyeliner), nail polish or other cosmetic that contains metal
- Dental fillings or braces (while usually unaffected by the magnetic field, these may distort images of the facial area or brain; the same is true for orthodontic braces and retainers)
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The MRI examination is performed in a special room that houses the MR system or “scanner.” You will be escorted into the room by a staff member of the MRI facility and asked to lie down on a comfortably padded table that gently glides you into and the scanner. The typical scanner is open on each end, or at least two sides.
In general, in preparation for the MRI examination, you will be required to wear earplugs or headphones to protect your hearing because many scanning procedures produce loud noises. These loud noises are normal and should not worry you.
For some MRI exams, a contrast agent called gadolinium may be injected into a vein to help obtain a clearer picture of the area being examined. Typically, at the beginning of the imaging procedure, a nurse or MRI technologist will place an intravenous line in your arm or hand vein using a small needle. This will allow injection of the gadolinium contrast agent.
The line will be connected to a saline solution that will drip through the intravenous line to prevent clotting until the actual contrast agent is injected at some point during the exam. Sometimes the contrast agent is injected with an automatic device and sometimes it is necessary for the technologist or nurse to come into the room to inject the contrast agent.
They may even have to slide the table the scanner to do this.
The most important thing for the patient to do is to lie still and relax. Most MRI exams take between 15 to 45 minutes to complete depending on the body part imaged and how many images are needed, although some exams may take up to 60 minutes or longer. You will be told ahead of time how long your scan is expected to take.
You will be asked to remain perfectly still during the time the imaging takes place, but between sequences some minor movement may be allowed. The MRI technologist will advise you, accordingly.
When the MRI exam begins, you may breathe normally. However, for certain examinations it may be necessary for you to hold your breath for a short period of time.
During your MRI examination, the MR system operator will be able to speak to you, hear you, and observe you at all times. Consult the MR scanner operator if you have questions or feel anything unusual.
When the MRI exam is over, you may be asked to wait until the images are examined to determine if more images are needed. After the exam, you have no restrictions and can go about your normal activities.
Once the entire MRI examination is completed, the images will be reviewed by a radiologist, a physician who has been specially trained to interpret the scans for your doctor.
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Some patients who undergo MRI examinations may feel confined, closed-in, or frightened. Perhaps one every twenty people may require a mild sedative to remain calm.
Today, many patients avoid this problem when examined in one of the newer scanners that have a more “open” design. Some MRI centers permit a relative or friend to be present in the MR system room, which also has a calming effect for the patient.
If patients are properly prepared and know what to expect, it is almost always possible to complete the examination.
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If you are pregnant or suspect you are pregnant, you should inform the MRI technologist and/or radiologist during the screening procedure that is conducted and before the MRI examination. In general, there is no known risk of using MRI in pregnant patients.
However, MRI is reserved for use in pregnant patients only to address very important problems or suspected abnormalities. In any case, MRI is safer for the fetus than imaging with x-rays or computed tomography (CT).
For additional information see MRI During Pregnancy.
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You should inform the MRI clinic that you are breast-feeding when scheduling your MRI exam. This is particularly important if you receive and MRI contrast agent.
One option under this circumstance is to pump breast milk before the MRI exam, which can be used to feed the infant until the contrast agent has been cleared from the body. It usually takes about 24 hours for the contrast agent to clear the body.
The clinic or radiologist will provide additional information to you regarding this matter.
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The MRI safety information on this page was developed in cooperation with the Institute for Magnetic Resonance Safety, Education, and Research (www.imrser.org) and from relevant content obtained from www.MRIsafety.com.
For more detailed MRI safety information, visit www.MRIsafety.com, which provides up-to-date and crucial MRI safety information, especially for screening patients with implants and medical devices.
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This page was reviewed on February 20, 2019
What Is MRI Scan? Uses, Safety, and Side Effects
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Picture: A medical technician prepares a patient for an MRI to check for a possible brain tumor
- Magnetic resonance imaging or MRI scanning uses magnetism, radio waves, and a computer to produce images of body structures.
- MRI scanning is painless and does not involve x-ray radiation.
- Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet.
- Claustrophobic sensation can occur with MRI scanning.
What is an MRI (magnetic resonance imaging)?
An MRI or magnetic resonance imaging is a radiology techinque scan that uses magnetism, radio waves, and a computer to produce images of body structures. The MRI scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet.
The magnet creates a strong magnetic field that aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal that is detected by the receiver portion of the MRI scanner.
A computer processes the receiver information, which produces an image.
MRI image and resolution is quite detailed, and it can detect tiny changes of structures within the body. For some procedures, contrast agents, such as gadolinium, are used to increase the accuracy of the images.
What are the uses for an MRI?
An MRI scan can be used as an extremely accurate method of disease detection throughout the body and is most often used after the other testing fails to provide sufficient information to confirm a patient's diagnosis. In the head, trauma to the brain can be seen as bleeding or swelling. Other abnormalities often found include brain aneurysms, stroke, tumors of the brain, as well as tumors or inflammation of the spine.
Neurosurgeons use an MRI scan not only in defining brain anatomy, but also in evaluating the integrity of the spinal cord after trauma.
It is also used when considering problems associated with the vertebrae or intervertebral discs of the spine. An MRI scan can evaluate the structure of the heart and aorta, where it can detect aneurysms or tears.
MRI scans are not the first line of imaging test for these issues or in cases of trauma.
It provides valuable information on glands and organs within the abdomen, and accurate information about the structure of the joints, soft tissues, and bones of the body. Often, surgery can be deferred or more accurately directed after knowing the results of an MRI scan.
Magnetic resonance imaging is a scan that produces detailed pictures of organs and other internal body structures while a CT scan forms images inside of the body. CT scans use radiation, which may be harmful to the body, while MRIs do not. MRIs cost more than CT scans.
Click for more of the differences between CT scans and MRIs »
What are the risks and side effecs of an MRI?
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An MRI scan is a painless radiology technique that has the advantage of avoiding x-ray radiation exposure. There are no known side effects of an MRI scan. The benefits of an MRI scan relate to its precise accuracy in detecting structural abnormalities of the body.
Patients who have any metallic materials within the body must notify their physician prior to the examination or inform the MRI staff. Metallic chips, materials, surgical clips, or foreign material (artificial joints, metallic bone plates, or prosthetic devices, etc.) can significantly distort the images obtained by the MRI scanner.
Patients who have heart pacemakers, metal implants, or metal chips or clips in or around the eyeballs cannot be scanned with an MRI because of the risk that the magnet may move the metal in these areas.
Similarly, patients with artificial heart valves, metallic ear implants, bullet fragments, and chemotherapy or insulin pumps should not have MRI scanning.
During the MRI scan, patient lies in a closed area inside the magnetic tube. Some patients can experience a claustrophobic sensation during the procedure. Therefore, patients with any history of claustrophobia should relate this to the practitioner who is requesting the test, as well as the radiology staff.
A mild sedative can be given prior to the MRI scan to help alleviate this feeling. It is customary that the MRI staff will be nearby during MRI scan.
Furthermore, there is usually a means of communication with the staff (such as a buzzer held by the patient) which can be used for contact if the patient cannot tolerate the scan.
How do I prepare for an MRI? How is it performed?
All metallic objects on the body are removed prior to obtaining an MRI scan. Occasionally, patients will be given a sedative medication to decrease anxiety and relax the patient during the MRI scan. MRI scanning requires that the patient lie still for best accuracy.
Patients lie within a closed environment inside the magnetic machine. Relaxation is important during the procedure and patients are asked to breathe normally. Interaction with the MRI technologist is maintained throughout the test.
There are loud, repetitive clicking noises which occur during the test as the scanning proceeds. Occasionally, patients require injections of liquid intravenously to enhance the images which are obtained.
The MRI scanning time depends on the exact area of the body studied, but ranges from half an hour to an hour and a half.
Health Screening Tests Every Woman Needs See Slideshow
When do I receive the results of an MRI?
After the MRI scanning is completed, the computer generates visual images of the area of the body that was scanned. These images can be transferred to film (hard copy).
A radiologist is a doctor who is specially trained to interpret images of the body. The interpretation is transmitted in the form of a report to the practitioner who requested the MRI scan.
The doctor can then discuss the results with the patient and/or family.
What does an MRI look (pictures)?
This patient had a herniated disc between vertebrae L4 and L5. The resulting surgery was a discectomy
Picture of herniated disc between L4 and L5Cross-section picture of herniated disc between L4 and L5
What new MRI scanners available?
Scientists are developing newer MRI scanners that are smaller, portable devices. These new scanners apparently can be most useful in detecting infections and tumors of the soft tissues of the hands, feet, elbows, and knees. The application of these scanners to medical practice is now being tested.
Medically Reviewed on 11/15/2019
REFERENCE: NIH. Magnetic Resonance Imaging (MRI).
Magnetic resonance imaging (MRI) is a type of scan that uses strong magnetic fields and radio waves to produce detailed images of the inside of the body.
An MRI scanner is a large tube that contains powerful magnets. You lie inside the tube during the scan.
An MRI scan can be used to examine almost any part of the body, including the:
- brain and spinal cord
- bones and joints
- heart and blood vessels
- internal organs, such as the liver, womb or prostate gland
The results of an MRI scan can be used to help diagnose conditions, plan treatments and assess how effective previous treatment has been.
During an MRI scan, you lie on a flat bed that's moved into the scanner.
Depending on the part of your body being scanned, you'll be moved into the scanner either head first or feet first.
The MRI scanner is operated by a radiographer, who is trained in carrying out imaging investigations.
They control the scanner using a computer, which is in a different room, to keep it away from the magnetic field generated by the scanner.
You'll be able to talk to the radiographer through an intercom and they'll be able to see you on a television monitor throughout the scan.
At certain times during the scan, the scanner will make loud tapping noises. This is the electric current in the scanner coils being turned on and off.
You'll be given earplugs or headphones to wear.
It's very important to keep as still as possible during your MRI scan.
The scan lasts 15 to 90 minutes, depending on the size of the area being scanned and how many images are taken.
Read more about how an MRI scan is performed.
Most of the human body is made up of water molecules, which consist of hydrogen and oxygen atoms.
At the centre of each hydrogen atom is an even smaller particle called a proton. Protons are tiny magnets and are very sensitive to magnetic fields.
When you lie under the powerful scanner magnets, the protons in your body line up in the same direction, in the same way that a magnet can pull the needle of a compass.
Short bursts of radio waves are then sent to certain areas of the body, knocking the protons alignment.
When the radio waves are turned off, the protons realign. This sends out radio signals, which are picked up by receivers.
These signals provide information about the exact location of the protons in the body.
They also help to distinguish between the various types of tissue in the body, because the protons in different types of tissue realign at different speeds and produce distinct signals.
In the same way that millions of pixels on a computer screen can create complex pictures, the signals from the millions of protons in the body are combined to create a detailed image of the inside of the body.
An MRI scan is a painless and safe procedure. You may find it uncomfortable if you have claustrophobia, but most people are able to manage it with support from the radiographer.
Going into the scanner feet first may be easier, although this isn't always possible.
Extensive research has been carried out into whether the magnetic fields and radio waves used during MRI scans could pose a risk to the human body.
No evidence has been found to suggest there's a risk, which means MRI scans are one of the safest medical procedures available.
But MRI scans may not be recommended in certain situations. For example, if you have a metal implant fitted, such as a pacemaker or artificial joint, you may not be able to have an MRI scan.
They're also not usually recommended during pregnancy.
Read more about who can and can't have an MRI scan.
What Is a MRI? What Happens When I Get One?
Magnetic resonance imaging (MRI) is a test that uses powerful magnets, radio waves, and a computer to make detailed pictures inside your body.
Your doctor can use this test to diagnose you or to see how well you've responded to treatment. Un X-rays and computed tomography (CT) scans, MRIs do not use the damaging ionizing radiation of X-rays.
A MRI helps a doctor diagnose a disease or injury, and it can monitor how well you’re doing with a treatment. MRIs can be done on different parts of your body. It's especially useful for looking at soft tissues and the nervous system.
A MRI of the brain and spinal cord looks for:
A MRI of the heart and blood vessels looks for:
A MRI of the bones and joints looks for:
- Bone infections
- Damage to joints
- Disc problems in the spine
- Neck or low back pain with nerve signs
MRIs can also be done to check the health of these organs:
- Breasts (women)
- Ovaries (women)
- Prostate (men)
A special kind of MRI called a functional MRI (fMRI) maps brain activity.
This test looks at blood flow in your brain to see which areas become active when you do certain tasks. A fMRI can detect brain problems, such as the effects of a stroke, or for brain mapping if you need brain surgery for epilepsy or tumors. Your doctor can use this test to plan your treatment.
Before your MRI, let your doctor know if you:
- Have any health problems, such as kidney or liver disease
- Recently had surgery
- Have any allergies to food or medicine, or if you have asthma
- Are pregnant, or might be pregnant
No metal is allowed in the MRI room, because the magnetic field in the machine can attract metal. Tell your doctor whether you have any metal-based devices that might cause problems during the test. These can include:
- Artificial heart valves
- Body piercings
- Cochlear implants
- Drug pumps
- Fillings and other dental work
- Implanted nerve stimulator
- Insulin pump
- Metal fragments, such as a bullet or shrapnel
- Metal joints or limbs
- Pacemaker or implantable cardioverter-defibrillator (ICD)
- Pins or screws
If you have tattoos, talk with your doctor. Some inks contain metal
On the day of the test, wear loose, comfortable clothing that doesn't have snaps or other metal fasteners. You might need to take off your own clothes and wear a gown during the test.
Remove all of these before you go into the MRI room:
If you don't enclosed spaces or you're nervous about the test, tell your doctor. You may be able to have an open MRI or get medicine to relax you before the test.
A typical MRI machine is a large tube with a hole at both ends. A magnet surrounds the tube. You lie on a table that slides all the way into the tube.
In a short-bore system, you are not totally inside the MRI machine. Only the part of your body that's being scanned is inside. The rest of your body is outside the machine.
An open MRI is open on all sides. This type of machine may be best if you have claustrophobia — a fear of tight spaces — or you're very overweight. The quality of images from some open MRI machines isn't as good as it is with a closed MRI.
Before some MRIs, you'll get contrast dye into a vein in your arm or hand. This dye helps the doctor more clearly see structures inside your body. The dye often used in MRIs is called gadolinium. It can leave a metal taste in your mouth.
You will lie on a table that slides into the MRI machine. Straps might be used to hold you still during the test. Your body might be completely inside the machine. Or, part of your body may stay outside the machine.
The MRI machine creates a strong magnetic field inside your body. A computer takes the signals from the MRI and uses them to make a series of pictures. Each picture shows a thin slice of your body.
You might hear a loud thumping or tapping sound during the test. This is the machine creating energy to take pictures inside your body. You can ask for earplugs or headphones to muffle the sound.
You might feel a twitching sensation during the test. This happens as the MRI stimulates nerves in your body. It's normal, and nothing to worry about.
The MRI scan should take between 20 and 90 minutes.
Pregnant women should not get a MRI during their first trimester unless they absolutely need the test. The first trimester is when the baby's organs develop. You also shouldn't get contrast dye when you’re pregnant.
Don't get contrast dye if you've had an allergic reaction to it in the past or you have severe kidney disease.
Certain people with metal inside their body can't get this test, including those with:
- Some clips used to treat brain aneurysms
- Pacemakers and cardiac defibrillators
- Cochlear implants
- Certain metal coils placed in blood vessels
A specially trained doctor called a radiologist will read the results of your MRI and send the report to your doctor.
Your doctor will explain the meaning of your test results and what to do next.
American Academy of Orthopaedic Surgeons: “X-Rays, CT Scans, and MRIs.”
FDA: “MRI (Magnetic Resonance Imaging).”
Mayo Clinic: “MRI: How you prepare,” “MRI: Risks.” “MRI: What you can expect,” “MRI: Why it's done.”
National Institute of Biomedical Imaging and Bioengineering: “Magnetic Resonance Imaging (MRI).”
Radiological Society of North America: “Magnetic Resonance Imaging (MRI) — Body.” “Magnetic Resonance, Functional (fMRI) — Brain.”
© 2019 WebMD, LLC. All rights reserved.
MRI Scans: Definition, uses, and procedure
A magnetic resonance imaging (MRI) scan is a common procedure around the world.
MRI uses a strong magnetic field and radio waves to create detailed images of the organs and tissues within the body.
Since its invention, doctors and researchers continue to refine MRI techniques to assist in medical procedures and research. The development of MRI revolutionized medicine.
This article looks specifically at MRI scans, how they work, and how doctors use them.
- MRI scanning is a non-invasive and painless procedure.
- Raymond Damadian created the first MRI full-body scanner, which he nicknamed the Indomitable.
- The cost of a basic MRI scanner starts at $150,000 but can exceed several million dollars.
- Japan has the most MRI scanners per capita, with 48 machines for every 100,000 citizens.
Share on PinterestMRI scans can produce a detailed image.
An MRI scan uses a large magnet, radio waves, and a computer to create a detailed, cross-sectional image of internal organs and structures.
The scanner itself typically resembles a large tube with a table in the middle, allowing the patient to slide in.
An MRI scan differs from CT scans and X-rays, as it does not use potentially harmful ionizing radiation.
The development of the MRI scan represents a huge milestone for the medical world.
Doctors, scientists, and researchers are now able to examine the inside of the human body in high detail using a non-invasive tool.
The following are examples in which an MRI scanner would be used:
- anomalies of the brain and spinal cord
- tumors, cysts, and other anomalies in various parts of the body
- breast cancer screening for women who face a high risk of breast cancer
- injuries or abnormalities of the joints, such as the back and knee
- certain types of heart problems
- diseases of the liver and other abdominal organs
- the evaluation of pelvic pain in women, with causes including fibroids and endometriosis
- suspected uterine anomalies in women undergoing evaluation for infertility
This list is by no means exhaustive. The use of MRI technology is always expanding in scope and use.
Share on PinterestA person can listen to music in headphones to mask the loud and sometimes alarming sound of the MRI machine.
There is very little preparation required, if any, before an MRI scan.
On arrival at the hospital, doctors may ask the patient to change into a gown. As magnets are used, it is critical that no metal objects are present in the scanner. The doctor will ask the patient to remove any metal jewellery or accessories that might interfere with the machine.
A person will probably be unable to have an MRI if they have any metal inside their body, such as bullets, shrapnel, or other metallic foreign bodies. This can also include medical devices, such as cochlear implants, aneurysm clips, and pacemakers.
Individuals who are anxious or nervous about enclosed spaces should tell their doctor. Often they can be given medication prior to the MRI to help make the procedure more comfortable.
Patients will sometimes receive an injection of intravenous (IV) contrast liquid to improve the visibility of a particular tissue that is relevant to the scan.
The radiologist, a doctor who specializes in medical images, will then talk the individual through the MRI scanning process and answer any questions they may have about the procedure.
Once the patient has entered the scanning room, the doctor will help them onto the scanner table to lie down. Staff will ensure that they are as comfortable as possible by providing blankets or cushions.
Earplugs or headphones will be provided to block out the loud noises of the scanner. The latter is popular with children, as they can listen to music to calm any anxiety during the procedure.
Once in the scanner, the MRI technician will communicate with the patient via the intercom to make sure that they are comfortable. They will not start the scan until the patient is ready.
During the scan, it is vital to stay still. Any movement will disrupt the images, much a camera trying to take a picture of a moving object. Loud clanging noises will come from the scanner. This is perfectly normal. Depending on the images, at times it may be necessary for the person to hold their breath.
If the patient feels uncomfortable during the procedure, they can speak to the MRI technician via the intercom and request that the scan be stopped.
After the scan, the radiologist will examine the images to check whether any more are required. If the radiologist is satisfied, the patient can go home.
The radiologist will prepare a report for the requesting doctor. Patients are usually asked to make an appointment with their doctor to discuss the results.
It is extremely rare that a patient will experience side effects from an MRI scan.
However, the contrast dye can cause nausea, headaches, and pain or burning at the point of injection in some people. Allergy to the contrast material is also seldom seen but possible, and can cause hives or itchy eyes. Notify the technician if any adverse reactions occur.
People who experience claustrophobia or feel uncomfortable in enclosed spaces sometimes express difficulties with undergoing an MRI scan.
An MRI scanner contains two powerful magnets. These are the most important parts of the equipment.
The human body is largely made of water molecules, which are comprised of hydrogen and oxygen atoms. At the center of each atom lies an even smaller particle called a proton, which serves as a magnet and is sensitive to any magnetic field.
Normally, the water molecules in the body are randomly arranged, but on entering an MRI scanner, the first magnet causes the water molecules to align in one direction, either north or south.
The second magnetic field is then turned on and off in a series of quick pulses, causing each hydrogen atom to change its alignment when switched on and then quickly switch back to its original relaxed state when switched off.
Passing electricity through gradient coils, which also cause the coils to vibrate, creates the magnetic field, causing a knocking sound inside the scanner.
Although the patient cannot feel these changes, the scanner can detect them and, in conjunction with a computer, can create a detailed cross-sectional image for the radiologist.
Functional magnetic resonance imaging (fMRI)
Functional magnetic resonance imaging or functional MRI (fMRI) uses MRI technology to measure cognitive activity by monitoring blood flow to certain areas of the brain.
The blood flow increases in areas where neurons are active. This gives an insight into the activity of neurons in the brain.
This technique has revolutionized brain mapping, by allowing researchers to assess the brain and spinal cord without the need for invasive procedures or drug injections.
Functional MRI helps researchers learn about the function of a normal, diseased, or injured brain.
fMRI is also used in clinical practice. Standard MRI scans are useful for detecting anomalies in tissue structure. However, an fMRI scan can help detect anomalies in activity.
In short, fMRI tests what tissues do rather than how they look.
As such, doctors use fMRI to assess the risks of brain surgery by identifying the regions of the brain involved in critical functions, such as speaking, movement, sensing, or planning.
Functional MRI can also be used to determine the effects of tumors, stroke, head and brain injuries, or neurodegenerative diseases, such as Alzheimer’s.
MRI scans vary from 20 to 60 minutes, depending on what part of the body is being analyzed and how many images are required.
If, after the first MRI scan, the images are not clear enough for the radiologist, they may ask the patient to undergo a second scan straight away.
I have braces or filings, should I still undergo the scan?
Although braces and fillings are unaffected by the scan, they may distort certain images. The doctor and technician will discuss this beforehand. The MRI scan may take longer if additional images are required.
Can I move while I am in the MRI tunnel?
It is important to stay as still as possible while in the MRI scanner. Any movement will distort the scanner and, therefore, the images produced will be blurry. In particularly long MRI scans, the MRI technician may allow a short break halfway through the procedure.
I am claustrophobic, what can I do?
The doctor and radiologist will be able to talk the patient through the whole procedure and address any anxieties. Open MRI scanners are available in some locations for certain body parts to help patients who have claustrophobia.
A person can take medication prior to the test to ease anxiety.
Do I need an injection of contrast before my MRI scan?
A contrast dye can improve diagnostic accuracy by highlighting certain tissues.
Some patients may need to have a contrast agent injected before the scan.
Can I have an MRI scan if I am pregnant?
Unfortunately, there is no simple answer. Let a doctor know about the pregnancy before the scan. There have been relatively few studies on the effect of MRI scans on pregnancy. However, guidelines published in 2016 have shed more light on the issue.
Typically, doctors do not recommend contrast material for women who are pregnant.
MRI scans should be restricted during the first trimester unless the information is considered essential. MRI scans during the second and third trimester are safe at 3.0 tesla (T) or less. The tesla is a measurement of magnetic strength.
The guidelines also state that exposure to MRI during the first trimester is not linked to long-term consequences and should not raise clinical concerns.