Radiation Continuing Concern with Fluoroscopy : Part 2

by Food and Drug Administration (FDA)

(Page 2 of 2)

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.

About the Author

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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.