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What is MRA?
How does MRI work?
Who can’t have MRI?
Is there any preparation for my MRI study?
I’m afraid I’ll feel claustrophobic inside the magnet. Can’t I just get an open MRI instead?
Where can I get my MRI/MRA study?
MRI (also known as MR) is a safe,
noninvasive diagnostic imaging procedure. MRI uses radio waves and a
magnet to produce precise, detailed images of various tissues in the body.
These images are used for detecting and treating various diseases in their
early stages, such as heart disease, stroke, and cancer. MRI can detect
disease in structures throughout the body including the brain, eyes,
heart, neck, shoulders, spine, heart, liver, kidney, spleen, pancreas, and
the pelvis and hips. MRI can also provide amazing images of joints in the
shoulder, wrist, ankle, and foot.
MRA stands for magnetic resonance
angiography. It uses the same technology as MRI, but is used specifically
to study blood vessels to detect stroke and disease in the head, neck,
lungs, kidneys, and legs. The preparation and procedure for MRA is the
same as for MRI. Typically a contrast material called gadolinium is
injected intravenously to make the blood vessels show up more clearly.
Because gadolinium is a natural mineral dye, patients are not prone to
allergic reactions.
Often patients confuse MRI with CT. While
CT uses x-rays to obtain images of the body, which exposes the patient to
small amounts of radiation, MRI DOES
NOT use x-rays. Instead, MRI uses radio waves, a magnet, and computer
software to obtain two- and three-dimensional (3D) images of the inside of
the body. The MRI system itself is composed of a large, circular tube
containing a powerful magnet. At Diagnostic Imaging Associates (DIA) we
use only high-field 1.5 Tesla (T) magnets. Tesla is a metric unit that is
related to the strength of the MRI unit’s magnetic field. Studies show
that a 1.5 T magnet produces the best images.
When the patient is inside the MRI unit’s
magnetic field, tiny particles in the body called protons are forced to
line up and spin in the same direction. While the protons are aligned,
radio waves are sent into the magnetic field. These signals disturb the
protons and make them spin in different directions. When the signal is
stopped, the protons line up again and release energy. This energy is
measured by the surface coils that are positioned around the area of the
body being studied. When turned on, the coils are like special antennae
that receive the energy. Diseased tissue emits response signals that vary
dramatically from those of normal tissue. The knocking or thumping heard
inside the magnet is the sound of the coils being turned on and off as
they measure the energy from the disturbed protons. The computer then
takes these measurements from the coils and constructs cross-sectional and
3D images of the body’s structures and tissues.
MRI scans are not recommended for patients
with pacemakers or any implants containing metal such as pins, screws, or
aneurysm clips. Patients with dental fillings or braces can have MRI
scans, though images taken around the mouth area may be distorted.
Because the long-term effects of MRI on an
unborn baby are unknown, pregnant women are usually advised against having
MRI.
Is there any preparation for my MRI study?
Before your MRI study, someone from our
office will call you to go over any necessary preparation requirements.
Typically patients are instructed not to eat four hours before their MRI
study.
What can I expect during my MRI study?
Before your MRI study, you will be asked
about any allergies and previous surgeries. You will also be asked
specific questions concerning pacemakers, metal plates or screws, or
surgical staples and aneurysm clips. If there is a possibility that you
have metal in your body, a screening x-ray may be taken to determine if
you can have MRI.
After your medical interview, you will be
asked to remove any jewelry, hair clips, hearing aids, or other objects
that may interfere with the MRI study. You may also be asked to change
into an examination gown if your clothes have metal buttons or zippers.
After changing into a patient gown, you will be led to the MRI suite. If
necessary, a contrast medium may be injected intravenously. Contrast is a
special liquid that highlights the tissue to make subtle differences or
pathology easier to see. Allergic reactions to contrast are rare. However,
if you feel discomfort or nausea at any time during the study, do not
hesitate to alert the technologist. You will be able to communicate with
the technologist via intercom throughout the entire study.
Next, the technologist will position you on
the table of the MRI unit. A surface coil will be positioned around the
part of the body being studied (eg, the shoulder). Surface coils act like
an antenna to receive the radio waves from the MRI system. It is normal to
feel heat around the area of the surface coil. But if at any time this
feeling becomes intense or uncomfortable, please alert the technologist.
It is better to stop and restart the test than suffer.
Once you are properly positioned, the table
will begin moving you into the MRI tunnel until the area being studied is
in the center of the magnet. It is essential that you remain completely
still during the study. You may even be asked to hold your breath. This is
because movement can blur the images, making the study less accurate.
Depending on your study, several different sequences may need to be
performed. A sequence is one set of images taken from a certain plane
through the body (eg, down the middle, or through the center). Depending
on which MRI study you are having and how many sequences need to be
performed, your examination can take anywhere from 10 minutes to almost an
hour.
For most patients, the technologist will
offer special goggles and headsets that heltp to block out the knocking
sounds of the surface coils. Patients can watch their favorite cable TV
shows or listen to the radio.
After the necessary images have been taken
and have been quickly reviewed for quality purposes, you will be free to
go home. The radiologist will then examine the films again in more detail
and report the findings to your referring physician. Your referring
physician will discuss the results with you and make a diagnosis based on
the findings and your medical history.
Yes. MRI involves no radiation and is
noninvasive. Some MRI studies do involve injecting a contrast medium which
can cause an allergic reaction. However, allergic reactions are rare and
may only involve a bad headache.
I’m afraid I’ll feel claustrophobic
inside the magnet. Can’t I just get an open MRI instead?
Before you request an open MRI over a
high-field study, it is important for you to be aware that all MRI units
are not created equal. Following are the Top Ten Reasons to Have a
High-field MRI:
- High-field MRI units actually have a
wider front to back opening than low-field (open) MRI units (60 cm versus
47 cm = 5 inches smaller, front to back).
- High-field MRI is typically
twice as fast as low-field MRI.
- High-field MRI has higher resolution,
which produces superior quality images with less blurring.
- High-field MRI can accurately show all
the structures and organs of small children because of its high
resolution, making it better for children compared with low-field MRI.
- High-field MRI produces thinner slices,
so smaller abnormalities won’t be missed.
- High-field MRI can detect early stroke
in 40 seconds with 100% accuracy. Low-field MRI cannot adequately do the
same.
- High-field MRI detects subtle calcium
deposits and hemorrhage (bleeding) that low-field MRI might miss.
- High-field MRI is preferred by most
medical specialists. Many specialists will not treat or operate based on
low-field MRI findings, which means you may have to obtain a repeat study
on high-field MRI.
- Insurance plans are starting to refuse
patients high-field MRI if they have already undergone low-field MRI. This
may delay your treatment by a specialist who is doubtful of your low-field
MRI findings.
- High-field MRI costs the same as
low-field MRI but offers you faster service and better quality images.
We understand that being inside the magnet
of a high-field MRI unit can be intimidating. In order to make our MRI
patients more comfortable, we offer special goggles and headsets that
allow the patient to watch TV shows or listen to the radio. With the
goggles and the extra-wide opening on our MRI units, we experience only a
1% rejection rate due to claustrophobia. This is the same rejection rate
as “open”, low-field MRI units. In addition, patients who tend toward
claustrophobia can have their referring physician prescribe intravenous
Valium, which they can pick up before coming to their MRI appointment.
Before the study, one of our radiologists or technologists will administer
the Valium.
Where can I get my MRI/MRA study?
Diagnostic Imaging Associates offers
high-field MRI studies at three convenient locations in
To schedule an appointment, please call the location nearest you.