MRI > Frequently Asked Questions by E27r96rf


									MRI - Frequently Asked Questions
What is an MRI?
MRI stands for Magnetic Resonance Imaging. It is a painless diagnostic
procedure which allows physicians to see detailed images of the internal
structures of your body without using X-rays. It uses a large magnet, radio
waves and a computer to scan your body.

Why is MRI important?
This technology is important because MRI scans illustrate more clearly than
ever before, the difference between healthy and diseased tissue, and can
provide important information about the brain, spine, joints and internal
organs. It can lead to early detection and treatment of disease and has no
known side effects. Consequently, your physician will be better able to
determine the most appropriate treatment for you.

Are there any contraindications to having an MRI?
Yes. There are contraindications to having an MRI. Due to the strong
magnetic field, some patients with certain types of surgically implanted
devices or objects cannot be scanned. Your physician will review your
medical history and determine whether or not an MRI scan can be performed
on you.

Can I have an MRI if I am pregnant?
It is considered wise to avoid scanning during the first trimester of pregnancy
unless deemed absolutely necessary by the physician. While no adverse side
effects have been proven from performing MRI during pregnancy, whenever
possible the MRI should be postponed until the pregnancy is over.

How does an MRI scanner work?
Your body is composed of small particles called atoms. Hydrogen atoms, i.e.
in water, make up 95% of the body. Normally, these hydrogen atoms within
your body spin around at random. However, when you are placed inside a
strong magnetic field, the hydrogen atoms line up and spin in the same
direction as the magnetic field. When a radio wave is transmitted through the
body, the hydrogen atoms give off a signal. That signal, with the aid of a
computer, becomes the source of MRI information to produce two-
dimensional images or three-dimensional volumes of a part of your body.

What causes the noise in the scanner?
The noise is due to the rising electrical current in the wires of the gradient
magnets being opposed by the main magnetic field. The stronger the main
field, the louder the gradient noise.
How long do I have to wait for an appointment?
The demand for an MRI is high and the waiting period for an MRI
appointment ranges from two to three months for most exams. Urgent
requests and emergencies are incorporated into the schedule as needed.
Once we receive a request for an MRI and the Screening Form, we will
schedule an exam date and contact your referring physician. The referring
physician will notify you of your exam time and date.

What should I do to prepare for my exam?
Some MRI procedures require patient preparation before the examination.
The MRI department will inform your doctor, who will in turn, inform you. If
you are claustrophobic, please ask your doctor to prescribe medication for
you, and bring it with you on the day of your appointment. We ask that you
also bring with you, any previous examination (X-ray, CT scan, etc.) that is
relevant to your MRI exam.

What does an MRI look like?
An MRI is a two-dimensional image or three-dimensional volume of a part of
your body. MRI images are viewed on a computer monitor and can be printed
on film (like an X-ray) or recorded on optical discs and compact discs. One
MRI exam consists of a series of MRI scans. Each scan ranges in length from
a few seconds to a few minutes and can contain any number of two-
dimensional images.

Will it hurt?
No. You will not feel anything. A call button will be given to you before the
exam is started. It will allow you to maintain two way communication with
the technologist at any time during the exam.

How safe is the MRI contrast dye? I had a reaction to the dye I was
given it in CT. Can I still be injected with MRI dye?
MRI contrast agents are very safe. They are different from those used in X-
rays, and are often used when X-ray contrast agents pose a risk to the

Will I see contrast dye in my urine if I have an injection?
No. The contrast agent used in MRI, called Gadolinium, is a clear, colourless
fluid, which is injected into a vein in your arm and is excreted by the kidneys
through your urine.
What areas of the body can you scan?
Any part of the body can be scanned on the MRI scanner. The body part
being scanned must be in the centre of the scanner and also near a piece of
the scanner (called a coil) designed to pick up information from the body,
and is usually shaped so that the body part will just fit into it. MRI machines
come with many different coils designed for imaging different parts of the
body: knees, shoulders, wrists, heads, necks, etc.

What is an MRA?
MRA stands for Magnetic Resonance Angiography, a special type of MRI that
looks at blood vessels and blood flow in virtually any part of the body with or
without injection of contrast. A major advantage of MRA is that it can be
performed as a non-invasive procedure which has little risk of complications
in comparison with conventional angiography or other related procedures. As
a result, MR Angiography is increasing in demand.

What is the difference between MRI and CT?
Both MRI and CT make cross-sectional images (slices) of almost any area of
the body using a sophisticated computer system. The major difference is that
while an MRI uses a large magnet and radio waves to produce images, a CT
scanner uses ionizing radiation. With the MRI studies, there is no exposure to
ionizing radiation and there are no known side effects. The systems
complement each other well as they both have their inherent strengths and
weaknesses. CT, however, can only directly acquire transverse and coronal
images, whereas MRI can directly acquire slices in any plane and is superior
when it comes to soft tissue contrast.

Can you scan my whole body while I'm in there?
No. With the MRI scanner, we can image almost any part of the body;
however, each scan is limited to a specific body part or area. It takes from
30 to 60 minutes to scan each area.

Why do I have to have my whole body in the scanner if you are only
scanning my head?
The part of the scanner that takes the pictures is located in the centre of the
scanner. Therefore, in order to do a scan of your head, most of your body
must slide into the scanner for proper positioning. The same is true for most
other studies of the spine and upper extremities.
Why do you need to know about metal implants in my head, if I'm
having my back scanned?
Although, we focus on one specific area when we scan you, your whole body
does go into the scanner. We need to know about metal anywhere in or on
your body because the magnet is never turned off, and just by entering the
scan room you come within the magnetic field. Certain metallic devices
interfere with the scan, and their presence during the scan may cause injury
to you. It is very important for us to know if you have a pacemaker or other
implanted electrical device, a history of heart or brain surgery, cerebral
aneurysm clips, shrapnel, or a history of getting metal fragments in your
eyes. Please check our MRI safety information section for more details.

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