What is a Functional MR Imaging (fMRI)?
- MRI uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissue, bone and virtually all other internal body structures. The images can then be examined on a computer monitor, transmitted electronically, printed or copied to a CD. MRI does not use ionizing radiation (x-rays).
- Functional magnetic resonance imaging (fMRI) is a relatively new procedure that uses MR imaging to measure the tiny metabolic changes that take place in an active part of the brain
- For our purposes, the MR image allows the researchers to evaluate various parts of the brain while you are performing a simple task in the scanner.
What are some common uses of the procedure?
- fMRI is becoming the method of choice for learning how a brain is working.
- For our research purposes, the fMRI image of the brain will give us better insight on which specific parts of the brain are being utilized while a participant is working on a task. Then we can compare healthy brain development and function to participants who have behavioral problems.
How should I prepare?
- You may be asked to wear a gown during the exam or you may be allowed to wear your own clothing if it is loose-fitting and has no metal fasteners.
- Unless you are told otherwise, you may follow your regular daily routine and take food and medications as usual.
- The radiologist should know if you have any serious health problems, or if you have recently had surgery.
- Females should always inform their physician or technologist if there is any possibility that they are pregnant.
- MRI has been used for scanning patients since the 1980s with no reports of any ill effects on pregnant women or their babies. However, because the baby will be in a strong magnetic field, pregnant women should not have this exam unless the potential benefit from the MRI exam is assumed to outweigh the potential risks. See the Safety page (http://www.radiologyinfo.org/en/safety/) for more information about pregnancy and MRI.
- We test all female participants for pregnancy before they enter into the machine. If you or your child declines the pregnancy test, she cannot participate in the research.
- Jewelry and other accessories should be left at home if possible, or removed prior to the MRI scan.
Because they can interfere with the magnetic field of the MRI unit, metal and electronic objects are not allowed in the exam 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.
- In most cases, an MRI exam is safe for patients with metal implants, except for a few types.
- People with the following implants cannot be scanned and should not enter the MRI scanning area unless explicitly instructed to do so by a radiologist or technologist who is aware of the presence of any of the following:
- Internal (implanted) defibrillator or pacemaker
- Cochlear (ear) implant
- Some types of clips used on brain aneurysms
- Some types of metal coils placed within blood vessels
You should tell the technologist if you have medical or electronic devices in your body, because they may interfere with the exam or potentially pose a risk, depending on their nature and the strength of the MRI magnet. Some implanted devices require a short period of time after placement (usually six weeks) before being safe for MRI examinations. Examples include but are not limited to:
- Artificial heart valves
- Implanted drug infusion ports
- Implanted electronic device, including a cardiac pacemaker
- Artificial limbs or metallic joint prostheses
- Implanted nerve stimulators
- Metal pins, screws, plates, stents or surgical staples
- In general, metal objects used in orthopedic surgery pose no risk during MRI. However, a recently placed artificial joint may require the use of another imaging procedure. If there is any question of their presence, an x-ray may be taken to detect and identify any metal objects.
- Participants who might have metal objects in certain parts of their bodies may also require an x-ray prior to an MRI. You should notify the technologist or radiologist of any shrapnel, bullets, or other pieces of metal which may be present in your body due to accidents. Foreign bodies near the eyes are particularly important.
- Dyes used in tattoos may contain iron and could heat up during MRI, but this is rarely a problem.
- Tooth fillings and braces usually are not affected by the magnetic field, but they may distort images of the facial area or brain, so the radiologist should be aware of them.
- We screen out all participants that have braces because the braces interfere with the images produced by the fMRI.
What does the equipment look like?
- The traditional MRI unit is a large cylinder-shaped tube surrounded by a circular magnet. You will lie on a moveable examination table that slides into the center of the magnet.
- The computer workstation that processes the imaging information is located in a separate room from the scanner.
- If you or your child is unsure about an fMRI machine and is a good fit in our study, our research group will make efforts to set up a tour of the fMRI before doing the scan so your child can familiarize himself or herself with the machine.
How does the procedure work?
- Unlike conventional x-ray examinations and computed tomography (CT) scans, MRI does not depend on ionizing radiation. Instead, while in the magnet, radio waves redirect the axes of spinning protons, which are the nuclei of hydrogen atoms.
- The magnetic field is produced by passing an electric current through wire coils in most MRI units.
- Other coils, located in the machine and in some cases, placed around the part of the body being imaged, send and receive radio waves, producing signals that are detected by the coils.
- A computer then processes the signals and generates a series of images, each of which shows a thin slice of the body. The images can then be studied from different angles by the interpreting radiologist.
- Frequently, the differentiation of abnormal (diseased) tissue from normal tissues is better with MRI than with other imaging modalities such as x-ray, CT and ultrasound.
- In an fMRI examination, you will perform a particular task during the imaging process, causing increased metabolic activity in the area of the brain responsible for the task. This activity, which includes expanding blood vessels, chemical changes and the delivery of extra oxygen, can then be recorded on MRI images.
- We’re interested in learning more about brain activity in children who have difficulties with their behavior. During the study, the child will be in an fMRI scanner doing simple computer games for about an hour. While the child is doing the computer games, we record his or her brain activity and compare children with behavior problems and children without behavior problems.
How is the procedure performed?
- You will be positioned on the moveable examination table. Straps and bolsters may be used to help you stay still and maintain the correct position during imaging.
- We will not use straps and bolsters.
- Devices that contain coils capable of sending and receiving radio waves may be placed around or adjacent to the area of the body being studied.
- For fMRI, your head may be placed in a brace designed to help hold it still. This brace may include a mask that is created especially for you. You may be given special goggles and/or earphones to wear, so that audio-visual stimuli (for example, a projection from a computer screen or recorded sounds) may be administered during the scan.
- We will be using a head brace, headphones and goggles. Please let the researchers know if your child has a history of claustrophobia.
- You will be moved into the magnet of the MRI unit and the radiologist and technologist will leave the room while the MRI examination is performed.
- During an fMRI exam, you will be asked to perform a number of small tasks, such as tapping your thumb against each of the fingers on the same hand, rubbing a block of sandpaper, or answering simple questions.
- For our tasks you will be asked to respond to a task by pushing buttons.
- When the examination is completed, you may be asked to wait until the technologist or radiologist checks the images in case additional images are needed.
- MRI exams generally include multiple runs (sequences), some of which may last several minutes.
- The entire examination is usually completed within an hour.
- MR spectroscopy, which provides additional information on the chemicals present in the body's cells, may also be performed during the MRI exam and may add approximately 15 minutes to the total exam time.
What will I experience during and after the procedure?
- Most MRI exams are painless. However, some people find it uncomfortable to remain still during MR imaging. Others experience a sense of being closed-in (claustrophobia).
- It is normal for the area of your body being imaged to feel slightly warm, but if it bothers you, notify the radiologist or technologist. It is important that you remain perfectly still while the images are being recorded, which is typically only a few seconds to a few minutes at a time.
- You will know when images are being recorded because you will hear tapping or thumping sounds when the coils that generate the radiofrequency pulses are activated. You will be able to relax between imaging sequences, but will be asked to maintain your position as much as possible.
- We do provide headphones that reduce the sound of the machine to a comfortable level.
- You will usually be alone in the exam room during the MRI procedure. However, the technologist will be able to see, hear and speak with you at all times using a two-way intercom. Many MRI centers allow a friend or parent to stay in the room as long as they are also screened for safety in the magnetic environment.
- You may be offered or you may request earplugs to reduce the noise of the MRI scanner, which produces loud thumping and humming noises during imaging. Children will be given appropriately sized earplugs or headphones during the exam. MRI scanners are air-conditioned and well-lit. Some scanners have music to help you pass the time.
Who interprets the results and how do I get them?
- A radiologist, a physician specifically trained to supervise and interpret radiology examinations, will analyze the images and send a signed report to your primary care or referring physician, who will share the results with you.
- Because this is a research experiment we cannot inform you of the results of the scan, however, all of our scans are reviewed by a physician and if anything abnormal is found you will be notified as soon as possible.
What are the benefits vs. risks?
- MRI is a noninvasive imaging technique that does not involve exposure to ionizing radiation.
- MRI can help physicians evaluate both the structure of an organ and how it is working.
- MRI enables the discovery of abnormalities that might be obscured by bone with other imaging methods.
- fMRI enables the detection of abnormalities of the brain, as well as the assessment of the normal functional anatomy of the brain, which cannot be accomplished with other imaging techniques.
- The MRI examination poses almost no risk to the average patient when appropriate safety guidelines are followed.
- Although the strong magnetic field is not harmful in itself, implanted medical devices that contain metal may malfunction or cause problems during an MRI exam.
- The fMRI is a minimal risk procedure, meaning the risks associated with it are comparable to risks associated with everyday life activities, like going to school. This doesn’t mean there are no risks; it just means the risks are similar to ones kids encounter in a typical day.
What are the limitations of fMRI of the Brain?
- High-quality images are assured only if you are able to remain perfectly still while the images are being recorded. If you are anxious, confused or in severe pain, you may find it difficult to lie still during imaging.
- A person who is very large may not fit into the opening of certain types of MRI machines.
- The presence of an implant or other metallic object sometimes makes it difficult to obtain clear images.
- Movement can have the same effect.
- Although there is no reason to believe that magnetic resonance imaging harms the fetus, pregnant women usually are advised not to have an MRI exam unless medically necessary.