MRI Frequently Asked Questions (FAQ)

MRI Frequently Asked Questions

Most patients who need a MRI have a lot of questions. MRI frequently asked questions, both recumbent and upright are summarized here for your reference. If you have any questions related specifically to your upcoming appointment, please contact our staff and we will be happy to assist you.

What is MRI?

Magnetic resonance imaging or scanning (MRI) is a method of looking inside the body without using surgery, harmful dyes or x-rays.

The MR scanner uses magnetism and radio waves to produce remarkably clear pictures of the human anatomy. When you are referred by your physician for an MRI, he or she is utilizing the most advanced method of diagnostic imaging available in the world today.

An MRI provides your physician with a great deal of information about your condition. If you are fortunate enough to be referred for a scan in a FONAR MRI machine, it will be a quick, comfortable and safe experience.

Although MRI is used for medical diagnosis, it utilizes a physics phenomenon discovered in the 1930s called nuclear magnetic resonance in which magnetic fields and radio waves, both harmless, cause atoms to give off tiny radio signals. In the 1940s, research physicists found that the length of time these response signals are emitted after an atom is stimulated by radio waves varies widely depending upon the substance being examined. This amazing phenomenon also holds true for biological tissue.

It wasn’t until 1970, however, that Raymond Damadian, a medical doctor and research scientist, discovered the basis for using magnetic resonance as a tool for medical diagnosis when he found that different kinds of animal tissue emit response signals that vary in length and, furthermore, that cancerous tissue emit response signals that last much longer than non-cancerous tissue.

He would subsequently find that the response times of other kinds of diseased tissue, normally called “relaxation times,” also vary dramatically. There are two kinds of relaxation times that can be detected and they are known as T1 and T2. When a patient is being scanned with magnetic resonance, the response signals emitted by the atoms in the patient’s body are picked up by a very sensitive antenna and forwarded to a computer for processing.

When the processing of these signals is complete, a two-dimensional, cross-sectional pattern is created on a monochrome monitor that looks very much like what you would expect if you took a black-and-white TV picture of that particular cross-section. In other words, this “image” shows much more detail than any images generated by X-rays-CAT scans also use X-rays, by the way-but the beauty of MRI is that it doesn’t use harmful X-rays.

Although this picture looks like a photo, it is not a photo. In fact, in the hands of a trained radiologist, the information it provides is much more useful than what would be revealed in a photo. A typical image is typically made up of 65,000 tiny rectangles that are either white, black or one of a wide range of gray tone values that fall somewhere between black and white. To a trained MRI radiologist, these gray tones speak volumes.

Why did my doctor order an MRI?

Whenever your doctor requires top-quality anatomic portrayal, especially soft tissue, chances are that an MRI will be the modality of choice. Unfortunately, the decision to prescribe or not to prescribe an MRI will not always be made on the basis of diagnostic quality.

Sometimes, in a well-meaning attempt to save money for the patient or the insurance company, a physician will choose a less-expensive procedure, hoping that he or she will receive sufficient information to make a correct diagnosis. If the less-expensive test proves inadequate, however, and an MRI is prescribed later, the attempt to save money will have been futile. Even worse, the condition may be inaccurately diagnosed using a less definitive, non-MRI procedure.

A recent court case helps illustrate the point. A Minnesota jury recently awarded a couple $1.25 million because two physicians treating their son, Philip, at Park Nicollet Medical Center failed to prescribe an MRI to assist them in making their diagnosis.

Over a period of 18 months beginning in the fall of 1989, they treated the boy for attention deficit hyperactivity (ADH). Finally, when no progress was noted, the parents took it upon themselves to consult a neurologist at the University of Minnesota. The specialist promptly prescribed an MRI and soon afterward properly diagnosed the boy’s condition as metachromatic leukodystrophy, a degenerative brain disease which can often be reversed with a bone marrow transplant.

For young Philip, however, it was too late. He had surgery for MLD in December 1991 and died in the summer of 1992. Had an MRI been prescribed without undue delay, chances are the boy would still be living.

Neurologists are just one medical specialty that depend a great deal upon MRI for accurate diagnostic information. Other medical specialties and healthcare providers that rely in great numbers upon MRI include neurosurgeons, orthopedic surgeons and chiropractors.

Because MRI portrays soft tissue with such diagnostically-useful clarity, it is relied upon frequently for revealing abdominal abnormalities-mid-field scanners are clearly superior to high-field scanners in this regard-and a wide variety of other ills as diverse as malfunctioning temporomandibular joints (TMJs) in the jaw, pinched nerves in the spinal column, heart disease and multiple sclerosis. (Nothing is superior to MRI for revealing MS.) From the beginning, of course, one of the great strengths of MRI has been its ability to reveal tumors.

Incidentally, don’t let the fact that MRIs provide great soft-tissue imaging mislead you into thinking that they aren’t great for many types of musculoskeletal imaging. In fact, the second largest application for MRI at present is musculoskeletal disease.

Orthopedic physicians regularly refer patients for MRIs for a wide variety of conditions. That’s why you hear so much, for example, about professional athletes getting MRI scans. FONAR has been a pioneer in the development of a number of specialized MRI diagnostic methods used in sports medicine. It has led the way, for example, in providing anatomical motion studies.

These studies enable technologists to electronically sequence a series of MRI images to create an accurate portrayal of how a malfunctioning joint in a patient is working dynamically. Individual MRI images reveal static conditions, just as a photo snapshot reveals a person’s likeness just for an instant of time, but misses the facial expression that occurred a second or two earlier and the one that followed immediately after.

A dynamic portrayal of a joint helps a physician understand how a particular joint-a shoulder, a knee, a neck or a TMJ-functions in “real life.” Incidentally, open-environment MRI scanners such as FONAR manufactures are clearly superior for these motion studies as they provide the space required for a patient to move their arm, leg or neck through a wide range of positions.

Magnetic resonance angiography (MRA) is a well-utilized procedure that will only increase in use by cardiologists in the future. Although CAT scans are better able to show calcified plaque that has built up in an artery, physicians will increasingly turn to MRA in the future to reveal the presence and severity of soft atherosclerotic plaque. In other words, it will reveal newer, more recent plaque which has formed, enabling physicians to view the extent of artery disease more accurately and to treat that disease more appropriately.

Incidentally, patients who require life-support systems – heart patients, for example – can be imaged in a FONAR MRI scanner. Although more and more non-magnetic devices are being developed for use around “supercon” scanners with large fringe fields, normal life-support systems with ferromagnetic components have been used around FONAR scanners for years because of their vertical magnetic fields.

Nothing is superior to an MRI for imaging breast implants. It shows the implants much more clearly than other modalities and it has the added advantage of not using X-rays, a particular concern when imaging the breast. MRI is also superior to ultrasound, X-ray mammograms or CAT scans when it comes to revealing malignancies in very dense breasts. This is still a developing area for MRI, one which will become much more dominant in the future. The MRI applications mentioned above are just a small portion of the applications for which MRI is the modality of choice.

If you have further questions, discuss them with your physician or speak with a radiologist who specializes in MRI. MRI is still a developing modality whose diagnostic power is becoming more and more appreciated with time. Already, it has replaced a great number of X-ray-based procedures and it is certain to replace even more in the future.

Are MRI scanners dangerous?

For the vast majority of people, there is no danger associated with having an MRI scan. For those people whose anatomy contains one or more of the following items, however, it is important to be aware of the possibility that an MRI could cause serious injury or death. Besides complete information about your medical history, your doctor and the MR staff must know if you have any metal in your body which cannot be removed, including:

• pacemakers
• implanted insulin pumps
• aneurysm clips
• vascular coils and filters
• heart valves
• ear implants
• surgical staples and wires
• shrapnel
• bone or joint replacements
• metal plates, rods, pins or screws
• contraceptive diaphragms or coils
• penile implants
• permanent dentures

In the case of metal implants, it is often possible for patients to be scanned without danger. It is very important, however, that you reveal the presence of such items to the radiologist and MRI staff in order for them to evaluate whether or not such danger exists. Also, it is important to tell a member of the staff if you are pregnant or if you believe there is a possibility you are pregnant.


In every MRI scanner, the patient lies in a strong magnetic field. Although the magnetic field is invisible and the patient cannot sense it, the strength of the field can be seen by its effect on a ferromagnetic object. For example, if one holds a metal paper clip in the “fringe” field surrounding an MRI scanner, one can feel the tug of the magnetic field on the paper clip, pulling it toward the center of the magnet.

In general terms, it may be said that the stronger the magnetic field, the stronger the pull. The strength of the pull will, however, be affected by the design of the magnet. Most MRI magnets have horizontal fields. These magnets exert a much stronger tug on metal objects located in their fringe fields than scanners with vertical-field magnets, an important safety point you might consider when choosing an MRI scanner.

Because metal objects brought inadvertently into the fringe field of a horizontal-field scanner can be propelled with great force into the center of the patient gap in such magnets, the potential for injury from flying objects does exist, although proper precautions make such accidents highly unlikely.

Nevertheless, this is one reason-though not the only reason-why FONAR scanners have vertically-oriented magnetic fields.

A metal object brought into the vicinity of a vertical magnetic field will be affected slightly by the field but will not be propelled toward the center of the magnet and thus endanger the patient. Some patients want to know why the scanner is in a special shielded room. This is because the scanner itself needs shielding from outside radio wave interference that can degrade the pictures.

The purpose of the shielding is the opposite of what it is for the CAT scanner (an X-ray machine) and other X-ray equipment. In the CAT scanner, its purpose is to shield the outside world from the CAT scanner’s X-rays.

Why are some MRI's "open" and some are not?

The highest field-strength scanners all use what are known as “superconducting” magnets. The reason such magnets are known as superconductors or “supercons” is that their magnets are comprised of miles and miles of special wire which, when immersed in a bath of liquid helium and initial connection to a power source, is capable of conducting electricity indefinitely, even when disconnected from the power source.

In order for this phenomenon to occur, the liquid helium must be maintained at a temperature of about minus 273.15 degrees Celsius, very close, in other words, to absolute zero, and the liquid helium must be replenished periodically. The architecture associated with such a magnet requires that the patient be positioned in the center of the magnet with the magnet coils surrounding the patient.

Thus, superconducting magnets are always shaped like a cylinder and the patient being scanned is positioned in a narrow, hollow tube in the center of the cylinder. This architecture is necessarily much less conducive to an open environment. It is therefore much more confining for the patient and, for some, much more claustrophobic. The architecture of vertical-field scanners are not restricted in the same way by the magnet design.

After Dr. Damadian constructed Indomitable, his prototype scanner, he determined that for commercial development of his scanner, he would forsake the superconducting type of magnet he had used for that machine, which required periodic, costly refilling with liquid helium, and that his next scanner would use a permanent magnet. Later, because of weight considerations that he had to overcome when he developed the world’s first mobile MRI scanner, he also designed a water-cooled, vertical-field electromagnet.

All of these commercial units have been “open” in their design and as the scientists at FONAR have developed more and more efficient magnet designs and coil systems, they have been able to increase that openness even more. For a long time, FONAR scanners have been known as the ones in which patients could spread out their arms and relax, free of claustrophobia. And in FONAR’s latest machine, the QUAD 7000, the vertical dimension within the patient gap has been increased by nearly 50 percent to its greatest height ever, unmatched by any other manufacturer.

For that reason, radiologists sometimes have to refer large or claustrophobic patients to FONAR machines, even if they are located some distance beyond the nearest competitive machine. If you are a larger patient, you shouldn’t have to be crammed into an MRI scanner with a shoehorn. If large patients who weigh 300 to 400 pounds fit into FONAR scanners but not those others, it stands to reason that a person weighing 130 pounds or 180 pounds will feel much less confined in a FONAR scanner.

Fortunately, there’s another option-the FONAR MRI Scanner. Some patients who are claustrophobic simply cannot tolerate lying down for extended periods of time in the confining spaces typical of most MRI scanners. Because of their claustrophobia, they often refuse to enter the scanner, even though an MRI may well prove critical for the accurate diagnosis of their illness. Even though these patients often admit their fear is irrational, for them it’s a fact of life.

If you are a patient with claustrophobic tendencies, you shouldn’t have to endure unnecessary anxiety just to get an MRI. Remember, however, that not all “open” MRI scanners are created equal. Most of them are underpowered and thus of diminished image quality. In some cases, that diminished image quality could be enough to cause a radiologist to miss an important detail, critical perhaps to an accurate diagnosis. A FONAR scanner provides both power and openness.

Why are MRIs so noisy?

Many MRI machines are noisy, but the multipositional scanner at the Vision Upright MRI Center contains special features that greatly reduce the noise level.

Not all MRIs are noisy but those that are noisy are noisy because of vibrating gradients, the adjunctive, non-uniform magnetic fields that enable the scanner to collect data from a particular cross-sectional plane. These gradient vibrations have been reduced to a minimum in the Vision Upright MRI Center scanner. For many patients, these “whisper quiet” gradients are a welcome change from the noise and stress associated with competitive machines.

Furthermore, because the main magnetic field in our multipositional scanner is vertical, enabling an open patient environment, what little noise is present is dissipated rather than concentrated. In fact, our machine is so quiet that patients often fall asleep.

It stands to reason, of course, that an open patient environment contributes to a relaxed patient and thus improved image quality. Optimum image quality, of course, translates into images that provide optimum diagnostic information to the radiologist.

Why do MRI scans take so long?

Fortunately, the time required for a scan is becoming shorter and shorter and the multipositional scanner at the Vision Upright MRI Center is making them even shorter.

The world’s very first whole-body scan in Dr. Damadian’s prototype machine took an exhausting four hours and 45 minutes. Most scans are now over in about 20 minutes, although it sometimes takes longer depending upon the anatomy or condition for which the patient is being scanned.

How do I prepare for an MRI?

Preparing for an MR scan is very easy. You can take all your normal medications and follow usual eating schedules unless your doctor gives you special instructions.

The only unusual preparation for an MR scan is that all removable metallic objects must be left outside the scanning room, including removable hearing aids, dentures and other prosthetic devices. Credit cards cannot be brought into the scanner room since the magnetic codes on them can be affected by the magnet.

For optimal image quality when performing head scans, all makeup must be removed since it may contain metallic powders which are magnetic and thus degrade image quality. You may be asked to wear a hospital gown, since clothes may have metallic fasteners or metallic fibers that can interfere with the imaging.

What does the MRI scanning center staff need to know about me to perform the scan?

Besides complete information about your medical history, your doctor and the MR staff must know if you have any metal in your body which cannot be remove including:

• pacemakers
• implanted insulin pumps
• aneurysm clips
• vascular coils and filters
• heart valves
• ear implants
• surgical staples and wires
• shrapnel
• bone or joint replacements
• metal plates, rods, pins or screws
• contraceptive diaphragms or coils
• penile implants
• permanent dentures

In most cases, you can be scanned even though you have metal implants. Nevertheless, the radiologist and MRI staff must be aware of them. Also, tell a member of the staff if you are pregnant or if there is a possibility you are pregnant.


What will happen when I get scanned?

A trained MR professional will help you into position on the scanner bed. This narrow bed slides directly into the scanner. Ask for a blanket if you are chilly. It may be necessary to place a special band or ring on the area to be scanned. This band or ring is actually a special antenna that enables the scanner to pick up signals with more clarity from that portion of anatomy that is being scanned.

Once you are positioned, all you have to do is relax and lie as still as you can. The Vision Upright MRI Center scanner is especially patient-friendly in this regard. Because it is so quiet and comfortable, many patients even fall asleep during the scan. You will be able to talk to a member of the staff in the next room who will be able to see and hear you during the entire scan. You can have a companion stay in the scanning room with you throughout the scan. In fact, whenever possible, parents are encouraged to be in the room with their children during the scan.

The procedure will take from 20 to 60 minutes depending on your doctor’s instructions. After the scan, you can resume all normal activities immediately. Infrequently, certain types of scans require the use of an injected contrast agent. If your doctor ordered this type of scan, our staff member will explain the contrast agent to you and answer your questions.

Isn't an MRI scan basically the same as a CAT scan?

No, except for the fact that they both use computers and they are both used for medical diagnosis, they really have very little in common. One of the most important differences between a CAT scan and an MRI is the fact that CAT scans use X-ray radiation and MRI scans do not, they use radio waves.

As you probably already know, X-rays can be harmful and it is important therefore to avoid unnecessary exposure to them. Although there are still some situations in which a CAT scan should be used instead of an MRI – your physician will be able to tell you when this is the case and why, for the most part, MRIs are diagnostically superior, especially if soft tissue is involved. If a CAT scan and an MRI are diagnostically equivalent in a particular situation, an MRI is the better choice because it will not subject you to any ionizing radiation. Instead, MRIs use harmless radio waves.

In addition to the superior portrayal of soft tissue, MRIs provide much more flexibility in portraying cross-sectional planes of the body. Unlike a CAT scanner which is relatively limited when it comes to plane selection, an MRI can provide a cross-sectional image taken at any plane in the human body.

Do you need a prescription for an MRI?

Yes. If you have reason to believe that an MRI would be beneficial in diagnosing your physical condition more accurately, discuss it with your doctor. If your doctor agrees, he or she will write a prescription. Let your doctor know that you would like to have your MRI scan performed at the Vision Upright MRI Center. If your doctor is unfamiliar with our center we can contact him or her to answer any questions in greater depth.

If I have an MRI scan, how will I find out the results?

Typically, your MRI scan will be examined or ‘read’ by a radiologist who is specially trained in MRI technology. At the Vision Upright MRI Center we have a superior staff that includes a Radiologist and certified technologists. The radiologist in will report to your physician, and your physician will then discuss the findings with you.

Can I choose the kind of MRI scanner I want?

Yes, you can. Your physician may have a business relationship with a particular diagnostic center and therefore prefer sending you to that particular site. If that imaging center is not Vision Upright MRI Center, you might consider asking for a referral in order to have the ability to stretch out your arms and relax in a quiet atmosphere while being scanned.

Only a doctor can prescribe an MRI, but you do have the right to request a scan in the machine of your choice. During your scan, if you feel like dozing, go ahead. It won’t hurt the scanning process at all and the technologist will give you a gentle wake-up call when your scan is completed.

Do I have to lie still when I have an MRI?

Yes, it is important to minimize movement in order to achieve the best imaging results. The quiet, restful environment and the multipositional scanner at the Vision Upright MRI Center is certainly conducive, of course, in helping a patient to be relaxed and to lie quietly.

Because a scanning session will often include a series of individual scans, you will probably be given the opportunity, and you can certainly request it beforehand, to find a more comfortable position in between one scan and the next. If you follow instructions as closely as possible, in all likelihood your images will be “just what the doctor ordered.”If you find that you are uncomfortable in any way, the attending technologist will be able to help you find a position in which you can rest comfortably. They will also have a number of “props” at their disposal that will help you “rest easy” and help them obtain the best picture possible.

What is the difference between T1 and T2?

Every tissue in the human body has its own T1 and T2 value. For example, white matter in the brain will exhibit different T1 and T2 values than that of blood. Both are different measures of different kinds of magnetic resonance “relaxation” that occurs after an atom has been stimulated by a radio signal in the presence of a strong magnetic field.

In magnetic resonance imaging, the emitted radio signal from a particular tissue depends on a combination of that tissue’s T1 and T2 values. In constructing an image, to help the radiologist make an accurate diagnosis, the MRI machine can use the tissue T1 to control the brightness of the image pixels (a T1 image) or it can use the tissue T2 to control the brightness of the image pixels (a T2 image).

Usually, a radiologist will request both T1 controlled and T2 controlled images. In a T1-controlled image, tissues with low T1 values will be displayed as bright picture elements, or pixels, on the computer monitor and tissues with high T1 values will be displayed with dark pixels. In a T2-controlled image, tissues with high T2 values will be portrayed as bright areas on the image and those with low T2 values as dark areas. Thus, a T1-controlled and a T2-controlled image for the same exact anatomical area can look quite different.

In a T1-controlled image, one particular spot may be bright white. In a T2-controlled image, the same identical spot may be displayed as gray. That’s because an MRI image is not a photograph. It is actually a computerized map or image of radio signals emitted by the human body. That’s the reason Dr. Damadian’s 1970 findings were so important. It is the variation in relaxation times of neighboring tissues that make each tissue distinguishable in an MRI image. If such were not the case, an image would be all one tone of gray and useless as a medical tool.

Dr. Damadian published his discovery that relaxation times of normal and cancerous tissue are markedly different and that relaxation times of normal, healthy tissues also vary significantly in the March 19, 1971 issue of Science. Less than two years later, he filed his idea for using magnetic resonance as a tool for medical diagnosis with the U.S. Patent Office. Entitled “Apparatus and Method for Detecting Cancer in Tissue,” and granted a patent by the Patent Office in 1974, it was the world’s first patent issued in the field of MRI. His patent contains the first conceptualization of a magnetic resonance scanner capable of cross-sectional scanning of a human being.

By 1977, Dr. Damadian had turned his concept into reality when he completed construction of the first whole-body MRI scanner, which he dubbed “Indomitable.” The name was a fitting choice. The large, strange-looking machine had been constructed despite those who said Dr. Damadian’s idea was impractical and foolish. Furthermore, on July 3, 1977, the nay-sayers were proven wrong when Dr. Damadian and his associates produced the first whole-body magnetic resonance image using Indomitable and the same signal-acquisition process described in Dr. Damadian’s patent.

Today, Indomitable is on permanent display in the Smithsonian Institution in Washington, DC.

What does the term "field strength" mean?

The strength of a magnetic field is measured in units of either Gauss or Tesla, where 10,000 Gauss units equal 1 Tesla. Based on these measurements, MRI scanners are often categorized as low-, mid- or high-field as follows:

Low-field MRI: 
Under 0.2 Tesla (2,000 Gauss)

Mid-field MRI: 
0.2 to 0.6 Tesla (2,000 – 6,000 Gauss)

High-field MRI: 
1.0 to 1.5 Tesla (10,000 – 15,000 Gauss)

For years, there was a debate among radiologists as to which range of field strengths was more effective diagnostically. High-field strength proponents would point to the fact that, other things being equal, the stronger the field, the stronger the amount of usable radio signal which can be elicited from the body’s atoms and, therefore, the higher the quality of the MRI image.

Low- and mid-field proponents pointed out, on the other hand, that though it was true that higher field strength meant more signal, that single advantage was offset by a number of disadvantages. With time and further research, that debate has largely become history.

Of particular significance was a carefully-conducted relaxometry study which found that optimum image contrast was to be found in the mid-field range. [Source: P.A. Rinck, et al., Radiology 168, (1988), 843-849.] Since differentiation between signals in an image is particularly important in arriving at a diagnostic conclusion, this study did much to confirm the arguments of those favoring mid-field scanners. A recent editorial in Applied Radiology by noted radiologist Dr. David Stark stated: “The great field strength debate lasted one decade. . . . Increasing field strength was an obvious, and expensive, approach to improve image quality.

Although it is unarguable that increasing field strength increases image quality by increasing image signal-to-noise ratios (SNR) achievable during a given scan time, over the past few years it has become apparent that increasing field yields only fractional gains in SNR, not the exponential bonanza touted in the 1980s.” Fortunately for MRI patients, there is a best-of-both-worlds solution to the field-strength question.

First, however, it should be pointed out that, because of their inability to harvest much of the available signal, low-field MRIs are largely deficient in image quality, a significant shortcoming when it comes to making an accurate diagnosis. Unfortunately, most so-called “open” environment MRI scanners fall into the low-field category.

Secondly, all FONAR scanners fall within the mid-field range when measuring the actual field strength. As a result, every one of them produces good image contrast, as proven by the relaxometry study cited earlier. Furthermore, because of their vertical-field orientation, FONAR scanners have a distinct advantage-an inherent advantage based on physics-over their horizontal-field competitors.

That’s because a vertical-field scanner is capable of using a particular type of antenna, known as a solenoidal surface coil, an antenna which a horizontal-field scanner cannot utilize. Together, the vertical-field magnet combined with the solenoidal surface coil double the signal-gathering capability of a horizontal-field scanner of the same field strength. Thus, a FONAR 0.3 Tesla scanner, the field strength at which most FONAR scanners operate, has the effective field of a 0.6 Tesla scanner.

FONAR is developing a 0.6 Tesla, open-environment scanner called the QUAD 12000 which has a measured field strength of 0.6 Tesla. Since it has a vertical field, however, and is thus capable of utilizing FONAR’s arsenal of super-efficient solenoidal surface coils, it is capable of achieving an effective field of 1.2 Tesla. This latest scanner is thus provides not only the 0.6 Tesla field strength found to provide maximum image contrast, it also provides the high-field strength capable of eliciting maximum signal from the human body-but with none of the detrimental drawbacks associated with a measured high field. When it is introduced, it truly will provide the best of both worlds.