Radiation Continuing Concern with Fluoroscopy
by Ricki Lewis, Ph.D. 

     In 1956, 7-year-old Steven Gold swallowed a penny.
Fortunately, the coin journeyed through the boy's system without
doing any harm. For a week, Steven's father, a doctor in general
practice, followed the penny's path by placing his son behind his
office fluoroscope screen. A fluoroscope is an x-ray device that
provides images of internal body parts as they move. When an
image appeared on the screen of Steven's insides, moving when he
squirmed, the route of the penny could be seen, a little farther
along each day.
     At that time, the fluoroscope was a standard piece of
medical equipment in some offices of family physicians. If a
patient came in with an arm dangling at an odd angle, for
example, the fluoroscope could rapidly reveal whether the bone
had been broken.
     Fluoroscopes were also used for a short time in a very
nonmedical setting--shoe stores. To determine shoe size, a
fluoroscope would reveal the length and structure of foot bones,
much to the delight of children who could see their skeletal toes
wiggle.
     Use of fluoroscopy in shoe stores was a rather frivolous
application of ionizing radiation, a form of energy that has the
potential to damage living tissue. "Fluoroscopy in shoe stores
was stopped because it wasn't necessary to expose people to
radiation when they wouldn't have much benefit. It was a sales
ploy, with fairly high exposures," says Thomas Shope, deputy
division director at the Center for Devices and Radiological
Health at FDA.
     In the 1960s, some doctors upgraded their fluoroscopic
equipment with a device called an image intensifier. This
produced brighter images, eventually allowing physicians to use
lower doses. Many family physicians opted to send patients to
radiologists or hospitals for x-rays. Meanwhile, fluoroscopy
found diverse nonmedical applications, such as screening airport
luggage for hidden metallic objects and detecting oil paintings
hidden behind other paintings.
     In fluoroscopy, as first observed by German physicist
Wilhelm K. Roentgen in 1895, x-rays strike a screen that is
coated with a fluorescent material. Because the radiation is
blocked more effectively by dense tissue, such as bone, than by
soft flesh, the result is a dark shadow of bones on the screen,
against a light background.
     "Fluoroscopy was originally done with a fluoroscopic screen,
which required that the radiologist sit in a darkened room until
he became dark-adapted to see the image in the low light level.
The x-ray image intensifying tube invented in the 1960s took the
place of the screen," says Shope.
     In today's fluoroscope systems, television or video cameras
can be attached to the image intensifier tube. "The camera output
can be digitized and sent through a computer, introducing
computer processing capabilities such as image enhancement,"
Shope adds. In cardiac catheterization, for example, a high-speed
version of the technology called cinefluorography images the 
working heart and its blood vessels, once the physician has
inserted the catheter using normal fluoroscopy.
     Today, fluoroscopy's ability to image moving internal body
parts has found application in guiding invasive medical
procedures. Snaking a catheter into an organ to biopsy a tumor is
safer and may reveal more information if the image is observed
with fluoroscopy, compared to the static images of other scanning
technologies. For example, fluoroscopy is essential to cardiac
catheterization, in which a catheter is inserted into a vein or
artery and guided into the interior of the heart to assess
blockage in the heart's arteries. The fluoroscope allows the
physician to see where the catheter is going. The catheter
delivers a contrast agent or monitors physiological function.
Fluoroscopy is also used to image the gastrointestinal (GI) tract
in a test commonly called a "GI series."
     In fact, the upper GI series accounts for 42 percent of all
fluoroscopy procedures. A patient drinks a chalky, milkshake-like
concoction containing barium, which coats the esophagus and
stomach. The barium absorbs the x-rays so that the lining of the
upper digestive tract can be visualized. In a lower GI series,
the patient receives a barium enema, which coats the intestines
and rectum. A gap in the image in the stomach or small intestine
could indicate an ulcer; bubbles in the normally smooth large
intestinal lining may be abnormal growths.
     Fluoroscopy can help patients regain lost functions. At
Royal Prince Alfred Hospital in Sydney, Australia, fluoroscopy is
being used to study throat movements in cancer patients who have
had their larynxes (voice boxes) removed. This type of analysis
helps physicians and speech pathologists identify and instruct
individual patients on new ways to produce some sounds. And at
Tel Aviv University in Israel, a fluoroscopically-guided catheter
is used to clear women's fallopian tubes of scar tissue that has
been preventing conception. Some previously infertile patients
have conceived within two months of treatment.
     Fluoroscopy can improve the safety of other procedures. For
example, blindly probing a tumor to remove cells for examination,
some surgeons believe, can actually spread the disease by
introducing cancer cells into the bloodstream. In an alternative
technique, physicians at Wuesthoff Memorial Hospital in
Rockledge, Fla., use a fluoroscope to guide a catheter in
biopsying cancerous tissue from a hard-to-reach kidney. Knowing
precisely which cell types are cancerous can aid a physician in
choosing the most effective therapy.
     Fluoroscopy is also useful in studying the esophagus. In a
procedure called Maloney dilation, a tube is passed through
constrictions in the esophagus to try to alleviate a persistent
feeling of having a lump in the throat. Done blindly, the
procedure is successful 80 percent of the time, but damages
delicate throat tissues up to 2.2 percent of the time.
Gastroenterologist Leslie E. Tucker, M.D., of Washington, Mo.,
reported in the American Journal of Gastroenterology on results
in 145 patients treated for a constricted esophagus with a
Maloney dilator and fluoroscopy. He found improved safety and
efficacy over using a dilator alone. When both techniques were
used, he reported, the rate of success rose to 96 percent, with
no injuries.
     Researchers at the University of Vienna used fluoroscopy to
visualize the esophagus in action. Wolfgang Schima and colleagues
compared videofluoroscopy to manometry, a standard technique that
measures pressure, in 92 patients who had difficulty swallowing.
A manometer is inserted into the nose, threaded down to the
stomach, then pulled back up to the lower esophagus. A microphone
is placed externally on the patient's throat, and as he or she
swallows, abnormal pressure changes are recorded, providing
diagnostic clues.
     In the fluoroscopy-assisted procedure used by Schima,
swallowing a pressure gauge is unnecessary. After drinking a
barium-containing liquid, the patient swallows, first in an
upright position, then lying down. A videofluoroscope records
throat movements during swallowing. Later, radiologists review
the videotape to see how the barium spreads as the patient
swallows. Whereas conventional x-rays can identify a structural
flaw in the esophagus, fluoroscopy reveals malfunction, such as a
spasm that might cause the lump-in-the-throat sensation, or poor
peristalsis (waves of muscle contraction) that stalls food. The
Viennese researchers recommend that videofluoroscopy become a
routine procedure for diagnosing a persistent lump-in-the-throat.

Safety Concerns
     The greatest concern about fluoroscopy continues to be
excessive radiation exposure. A single session for an invasive
medical procedure can take an extended time, sometimes lasting
more than an hour. FDA is currently analyzing the precautions
that can be taken in the use of the technology.
     "We are going to see an effort by the FDA and professional
organizations such as the American College of Radiology to put a
higher profile on encouraging education" of physicians in safe
fluoroscopy operation, says J. Thomas Payne, M.D., chairman of
the American College of Radiology's Commission on Physics and
Radiation Safety.
     Since receiving a number of reports of alleged patient
injury from long exposures to high-dose fluoroscopy, FDA has
intensified efforts to minimize exposures, evaluate risks,
develop ways to ensure safety of equipment and adequate training
of operators, and identify situations in which prolonged
exposures may occur. According to CDRH, two factors contribute to
the potential public health concern about fluoroscopy. First is
the increasing use of fluoroscopy to guide catheters, which
requires longer exposure times and for which physicians other
than radiologists may handle the x-ray equipment. Second, the
increasing complexity and capabilities of some newer fluoroscopy
systems require greater skill to operate.
     Payne published a warning to users outlining how
overexposure great enough to cause a severe radiation burn might
occur. In 1974, when FDA established x-ray safety standards, most
devices emitted 10 roentgen per minute. A roentgen (R) is a unit
for the quantity of radiation emitted. Today, more efficient x-
ray systems can produce 20 to 120 R per minute, a variation
called "high-level control mode." Also, in 1967, when fluoroscopy
was used for direct imaging rather than guiding catheters, 
exposure times were shorter. Payne describes a 100-minute-long
procedure guided by fluoroscopy emitting 20 R per minute. That
amounts to an exposure of 2,000 R, enough to cause a serious burn
if delivered to one part of the body. To put that into
perspective, most diagnostic x-rays use less than 1 R.
     Such observations have alerted the medical community to take
measures to enhance the safety of fluoroscopy. A recent workshop
sponsored by the American College of Radiology in Herndon, Va.,
to address this issue produced some valuable recommendations.
These include:
-    instituting separate controls for regular- and high-exposure modes of operation, so a
patient cannot inadvertently be given too high a dose
-    developing "last image hold capability," so that a physician finding a revealing view
can "freeze frame" it, rather than continuing to expose the patient.
     The dynamic nature of fluoroscopy makes it a valuable medical tool. Today,
fluoroscopy--with proper controls--will continue to help doctors view the body's insides in
action. 

Ricki Lewis is the author of textbooks on biology and human
genetics.
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