Fluoroscopy

A fluoroscope is an x-ray machine that produces a live picture on a television monitor. The x-ray beam is directed toward the patient, with an image receptor, in place of film, on the opposite side of the patient. The image receptor transmits the picture electronically to a monitor where the moving image can be observed. Equipment of this type can have an under or over-table tube configuration with sliding tube or image receptors, or a C-arm configuration with a rotating gantry.

Figure 4. Fluoroscopic Image Showing Blood Flow in the Brain

In the use of fluoroscopic equipment, the major problem in protecting personnel from radiation exposure arises from the long periods during which the beam is on. While the intensity of the direct beam is lower than in radiography, the exposure periods may be several minutes or more. In general, physicians, nurses, and x-ray personnel are present in the room during the exposure.

The dose rate from the direct x-ray beam for most fluoroscopic equipment is limited to 5 rem per minute at the entrance point of the patient. Even when exposure to personnel is reduced by 1000 times at one meter, this is still a dose rate of 5 mrem per minute! At this rate, a worker would only be able to spend 17 hours per year doing fluoroscopy. Fortunately, exposure rates are not often this high. Some fluoroscopy equipment has a high-level (boost) feature. In this mode, exposure rates can exceed those listed above. When the boost mode is activated, a constant audible signal is required to remind personnel of the radiation hazard.

Figure 5. Fluoroscopic X-Ray Equipment

Several radiation protection methods are necessary to ensure that personnel exposures are maintained ALARA in the use of fluoroscopy:

• All personnel must wear a protective apron when in the room during an exposure.
• Workers should not place themselves in the direct beam (usually hands and forearms receive this type of exposure).
• Personnel should be monitored for radiation exposure (film badges). When wearing a protective apron, the dosimeter should be placed outside the apron at the collar.
• Personnel allowed in the room during exposure must be restricted to essential patient care personnel.
• Where possible, the distance between the patient and personnel should be maximized.
• The fluoroscopy equipment must have a timer that alarms every five minutes of fluoroscopic time to alert personnel of accumulating dose.

Cineradiography is another method of producing moving images using x-rays. This procedure uses permanent film, as in radiography, but in a motion picture format similar to movie film. Exposures from cineradiography are higher than in fluoroscopy, and great care must be taken to reduce personnel doses.

Equipment design plays an important role in personnel exposure. Personnel who work routinely with fluoroscopic and cineradiographic equipment should become familiar with the individual characteristics of each machine.

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