- What
is MRI?
- What is the difference
between T1 and T2?
- Are MRI scanners
dangerous?
- What does
the term "field strength" mean?
- Why are some MRI's "open" and some are not?
- Why are MRIs
so noisy?
- Why do MRI
scans take so long?
- How do I
prepare for an MRI?
- What does the MR
scanning center staff need to know about me to
perform the scan?
- What will happen
when I get scanned?
- Isn't an MRI
scan basically the same as a CAT scan?
- Do
you need a prescription for an MRI?
- If I have an
MRI scan, how will I find out the results?
- Can
I choose the kind of MRI scanner I want?
- Do I have to
lie still when I have an MRI?
- When is an MRI
called for?
Q: What
is MRI?
A: Magnetic
resonance scanning or imaging (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 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.
Back to FAQ
Q: What is
the difference between T1 and T2?
A: 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.
Back to FAQ
Q: Are MRI
scanners dangerous?
A: 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.
IMPORTANT:
DO NOT ALLOW YOURSELF
TO BE SCANNED IF YOU HAVE A PACEMAKER OR OTHER
IMPLANTED MECHANICALLY, ELECTRICALLY OR MAGNETICALLY
ACTIVATED DEVICE. UNLESS SPECIFICALLY ORDERED
BY THE RADIOLOGIST, YOU WILL NOT BE SCANNED IF
YOU HAVE METAL IMPLANTS IN THE HEAD REGION.
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.
Back
to FAQ
Q:
What does the term "field strength"
mean?
A: 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 Gauss
to 6,000 Gauss)
- High-field MRI: 1.0 to 1.5 Tesla (10,000 Gauss
to 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.
Back
to FA
Q: Why are some MRI's "open"
and some are not?
A: The
answer to this question is related somewhat to
the previous answer. 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.
Back to FAQ
Q: Why
are MRIs so noisy?
A: 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 FONAR scanners. 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 FONAR scanners is vertical,
enabling an open patient environment, what little
noise is present is dissipated rather than concentrated.
In fact, FONAR machines are so quiet that patients
often fall asleep in them. 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.
Back to FAQ
Q: Why do MRI scans take so
long?
A: Fortunately,
the time required for a scan is becoming shorter
and 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.
Back to FAQ
Q: How
do I prepare for an MRI?
A: 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.
Back to FAQ
Q: What does
the MR 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 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 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.
IMPORTANT:
DO NOT ALLOW YOURSELF TO BE SCANNED IF YOU HAVE
A PACEMAKER OR OTHER IMPLANTED MECHANICALLY, ELECTRICALLY
OR MAGNETICALLY ACTIVATED DEVICE. UNLESS SPECIFICALLY
ORDERED BY THE RADIOLOGIST, YOU WILL NOT BE SCANNED
IF YOU HAVE METAL IMPLANTS IN THE HEAD REGION.
Back to FAQ
Q: What
will happen when I get scanned?
A: 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. FONAR scanners
are especially patient-friendly in this regard.
Because they are 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.
Back to FAQ
Q: Isn't
an MRI scan basically the same as a CAT scan?
A: 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. In other words,
CAT scans are nothing more than computerized X-rays.
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 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
to when it comes to plane selection, an MRI can
provide a cross-sectional image taken at any plane
in the human body.
Incidentally, the first MRI
company that made it possible to provide images
that were oblique to one of the three orthogonal
planes was FONAR Corporation. That was back in
1984. A year later, FONAR was the first to introduce
generalized oblique imaging, making it possible
to portray absolutely any cross-sectional plane
within the human body. In 1985, FONAR also introduced
Multi-Angle Oblique(TM) imaging, a patented technique
that made it possible to produce from one scan
a series of oblique images, each of which could
be individually oriented at a different angle.
The breakthrough was especially useful in obtaining
from one spine scan a cross-sectional image of
each intervertebral disc, none of which tend to
be precisely parallel to any other disc, helping
radiologists and attending physicians to easily
recognize herniation or to compare degenerative
changes that might be taking place in a patient's
spine. No other diagnostic modality provides such
imaging versatility.
Back to FAQ
Q: Do
you need a prescription for an MRI?
A: 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 refer you
to a local MRI diagnostic center for a scan.
Back to FAQ
Q: If I have an MRI scan, how
will I find out the results?
A: Typically,
your MRI scan will be examined or 'read' by a
radiologist who is specially trained in MRI technology.
The radiologist in turn will report to your physician,
and your physician will then discuss the findings
with you.
Back to FAQ
Q: Can
I choose the kind of MRI scanner I want?
A: 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 does not use a FONAR scanner,
you might consider asking for an alternative 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.
Back to FAQ
Q: Do
I have to lie still when I have an MRI?
A: Yes,
it is important to minimize movement in order
to achieve the best imaging results. The quiet,
restful environment of a FONAR scanner 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.
Back to FAQ
Q: When
is an MRI called for?
A: 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 and 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.
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