Can Magnetic Imaging Help Diagnose Knee Injuries?

QUESTION: Can magic imaging help diagnose knee injuries?
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ANSWER: That's "magnetic resonance" imaging or MRI, and while it is not
magic, it is very helpful in diagnosing many different conditions. MRI works
on a completely different principle from that of x-ray imaging or computed
tomography (CT or CAT scanning), which both used x-rays.
In MRI, x-rays are not used at all. The patient is placed in a machine
that creates a strong magnetic field, which causes the hydrogen atoms in that
body (and there are a lot, hydrogen is extremely common) to line up and point
in the direction of the field. A short pulse of radio waves then causes these
atoms to wobble a bit and then go back to spinning in alignment. This wobble
releases some of the radio energy back and depending on the density of
hydrogen in the tissues, different tissues send back different signals. These
signals are processed into computerized pictures of the tissues.
Unlike X-rays, the MRI process does not "see" bone tissue, because it
lacks hydrogen atoms, but it is excellent for soft tissues, which may be seen
even more clearly without being hidden by the dense bone. MRI imaging offers
great accuracy for diagnosis especially in structures like the knee, which are
made up of many types of tissue. Physicians can examine the knee for damage
to the muscles, ligaments and tendons, as well as for tumors, cysts, and
changes in the joint fluid.
There are no known adverse affects to MRI, although some people feel
claustrophobic while in the machine. Another plus is that there is no need to
inject any contrast materials into the joint to make certain features stand
out. However, MRI is expensive, but the cost is coming down as it is becoming
more widely used.