Background
Fluoroscopy
is an imaging technique that uses x-rays to obtain real-time moving images of
the interior of an object. By using a fluoroscope,
a physician can see the internal structure and function of body systems. Essentially,
a fluoroscope consists of an x-ray source and a fluorescent screen, between
which a patient is placed. For many decades, fluoroscopy produced live pictures
that were not recorded; since the 1960s, recording and playback has become
standard. Fluoroscopy combined with videotaping is especially useful for
evaluating the kinematics of joints.1
Historical Overview
In 1895, Wilhelm Röntgen noticed a barium platinocyanide screen
fluorescing after being exposed to x-rays. Within months, the first experimental
fluoroscopes were developed. In the late 1890s, Thomas Edison began
investigating materials such as calcium tungstate for their ability to
fluoresce when x-rayed. By the early 1900s, he had invented a fluoroscope with
sufficient image intensity to be commercialized. The introduction of analog
electronics revolutionized fluoroscopy. The development of the x-ray image
intensifier in the late 1940s and of closed-circuit TV cameras in the 1950s
produced brighter pictures and better protection from radiation, allowing the
radiologist to view the images in a separate room. In the early 1960s, digital
electronics were used to produce the first image to be digitally generated in
real-time; square-wave signals were detected by the pixels of a cathode ray
tube to create the image. After the late 1980s, digital imaging technology was
reintroduced to fluoroscopy with the development of improved detector systems. Modern
advancements continue to increase image quality while minimizing radiation exposure.2
Description
X-rays can penetrate a wide variety of objects, but they are
invisible to the naked eye. Conventional, film-based radiography makes the
x-ray penetrations visible through chemical changes in the film, and classic
fluoroscopy achieves this by fluorescence, whereby certain materials convert x-ray
energy into visible light. As the x-rays pass through the patient, they are attenuated
as they pass through or reflect off different tissues of the body and cast an x-ray
shadow of the radiopaque tissues on the fluorescent screen. Images on the
screen are produced as the unattenuated x-rays from radiolucent tissues
interact with atoms in the screen through the photoelectric effect.2
