The nuclear magnetic resonance (NMR) diagnostic
technology, which enables examining physicians to see operable
tumors, creates a magnetic field up to 40,000 times greater
than that of the Earth - and then depends on copper for the
integrity of its images.
When evaluated by NMR, a patient's body is placed inside a powerful
magnet where radio waves measure the effect of the magnetic
field on atomic nuclei in body cells. Shielding, particularly
copper shielding, is needed to prevent outside radio frequency
signals from distorting the signals and images. Examples of
outside signals that must be blocked for effective NMR characterization
include fluorescent lights, computers, radios, other diagnostic
equipment, and electromagnetic interference from power lines
and motors (e.g., elevators and large AC systems).
Absolutely fool-proof shielding is needed because the slightest
leak could permit radio waves to enter and distort the diagnostic
image.
The result is computerized images of the body's soft tissue
and internal chemistry, far more detailed than is possible with
conventional X-rays or CAT-scan equipment, and without the harmful
radiation of the latter two systems.
Copper is the preferred material for shielding NMR equipment
because it can be easily formed and soldered, it is more leak-proof,
it is installed faster, and is more economical in the long run.
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