Radiation Continuing Concern with Fluoroscopy

by Food and Drug Administration (FDA)

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.

About the Author

www.fda.gov
FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.