An
X-ray is a form of electromagnetic radiation of the same form
as visible light, but of an extremely short wavelength (less
than 100 angstroms). X-rays have the property of acting on
photographic plate to produce images. X-rays can also penetrate
solid material. For this reason, X-rays can be used to generate
pictures "through" a solid object, e.g. allowing inspection
of the contents of a suitcase or visualization of the interior
of a patient's body. X-rays also penetrate different materials
at different speeds; more dense material shows up as white
on an X-ray photograph, while less dense material shows up
gray or black. For this reason, X-rays can be used to differentiate
bone from soft tissue (allowing assessment of fractures) or
normal tissue from
diseased tissue (allowing detection of tumors).
X-ray images are two-dimensional, which
means that depth information is lost. Also, X-ray photography
cannot distinguish between two objects of the same density
(both will appear as the same brightness on the photographic
image).
Repeated or high-level exposure to X-rays
and other radiation can damage cells in the body by damaging
DNA and inhibiting the ability of cells' to reproduce. For
this reason, targeted exposure to radiation is used to inhibit
growth of tumors in some cancer patients.
Current techniques including computed
tomography (CT) make use of X-rays to construct detailed
images of the interior of the body and brain.

by Catherine E. Myers. Copyright © 2006 Memory Loss and the Brain |