American College of Radiology
kill more cancer cells while sparing
normal ones are also parts of this
century of remarkable progress.
The earliest X-ray images were
more useful to surgeons than to other
doctors. Bone fractures or displacements,
gallstones, kidney stones, and
bullets or other metallic fragments
could be located reliably. With the
improved tubes and films that
relaced the original glass plates,
doctors began to see organ shapes.
But they still could not see into
organs, which had the same water
density inside and out.
Nevertheless, other advances
came quickly. In 1896, the inventor
Thomas Edison devised the fluoroscope,
a calcium tungstate coated
screen which glowed when X rays hit
it, allowing direct viewing of any part
of the anatomy. In 1913, William D.
Coolidge of the General Electric
Laboratories devised an improved hot
cathode X-ray tube, which produced
consistent repeated exposures and
was shielded to prevent the scattered
radiation that had harmed the early
X-ray users. X-rays emerged from
Coolidge’s tubes only through an
aperture in the lead shielding. The
patient could then be placed into the
beam while others were kept away
from it. Additionally, filters were
devised to absorb soft, useless X rays,
and a device called a grid, placed in
front of the film, absorbed much of
the X-ray scatter that could cause
fuzzy images. Screens similar to the
fluoroscope surface were used in film
holders to enhance X-ray images.
And the problem of looking
within body structures was finally
addressed as well. Liquids opaque
to X rays were found that could