Fluoroscopy

Fluoroscopy is a technique that employs x-rays to generate real-time still images or video of a patient's body. The x-rays pass through the body and create an image on a detector, which is then transmitted to a monitor for viewing by the physician. Thus, a part of the body that is radio-opaque or made so by the use of a dye or a contrast agent can be visualized. Similarly, an instrument or device or movement of internal body parts can be displayed. ^{[1, 2, 3]}

It is a commonly used medical technique that helps physicians with a wide variety of diagnostic and interventional procedures. Although low doses are used, in prolonged procedures, the cumulative exposure may result in a relatively high absorbed dose to the patient. Therefore, all necessary precautions should be used, and the benefits should outweigh the potential risks in a given clinical situation. ^{[4, 5, 6, 7, 8]}

Because fluoroscopy involves the use of ionizing radiation, it is relatively contraindicated in pregnant women because of potentially harmful effects on a developing fetus.

This review focuses on the use of fluoroscopy in orthopedic procedures.

Fluoroscopy is used in many types of examinations and procedures. Some examples include the following:

• Orthopedic procedures, such as manipulation of broken bones in fracture reduction or insertion of implants and checking appropriate positioning or alignment.

• Gastrointestinal investigations using contrast agents, such as barium in the intestine to study its outline and movement.

• Cardiovascular and interventional radiology procedures, such as catheter insertion and monitoring of its progress (eg, to undo a blockage or insert a stent).

A fluoroscope in its simplest form (although rarely, if ever, used now) is an x-ray source at one end and a fluorescent screen at the other end. The part of the body that is to be imaged is placed between these ends. Low-dose radiation is used, and modern fluoroscopes couple the screen to an x-ray image intensifier to brighten the image sufficiently so as to be displayed as still images or video on a monitor. Recent advances allowing digitalization of the images and the use of flat panel detector systems have helped to further decrease the dose of radiation used.

Current equipment and safety measures help reduce the risks associated with fluoroscopy, including the following:

• Display of the duration, rate, and cumulative amount of radiation exposure patients receive. ^[1]

• Increased x-ray filtration to reduce the possibility of radiation injuries during long procedures.

• Tighter controls on the size of the x-ray field to reduce the amount of radiation that falls outside the image target area.

• A last-image-hold feature that allows the physician to view images without continually exposing patients to radiation.

• Use of a laser localization attachment to the C-arm helps position the x-ray source precisely over the area under scrutiny and minimizes repeat exposures due to imprecise positioning

Fluoroscopy involves the use of ionizing radiation and, therefore, carries the same types of risk as other x-ray procedures. The radiation dose a patient receives depends on a variety of factors, including the body part examined and the duration of the procedure. ^{[9, 10, 11]} The exposure and dose required in an obese patient is greater than in a lean patient, and abdominal fluoroscopy results in a greater exposure than fluoroscopy of the hand or wrist because of the increased thickness and tissue density of the abdomen. ^[4]

Two types of risks are associated with fluoroscopy (and other ionizing radiation exposures):

• Deterministic risks: The risk is nonexistent below a certain threshold of radiation dose, but it is nearly 100% at dose levels significantly greater than this threshold (eg, radiation burns to the skin and radiation-induced cataracts).

• Stochastic risks: The risk is directly proportional to the radiation dose, with no minimum dose below which the risk is zero (eg, radiation-induced cancer).

In practice, a risk of radiation burns exists only when fluoroscopy is conducted over prolonged periods of time and with the use of higher doses of radiation. Regarding stochastic risks, the "as low as reasonably achievable" (ALARA) principle applies in that the radiation dose should be made as small as reasonably achievable to reduce these risks to an absolute minimum. When a medical need exists, however, the benefit of fluoroscopy usually far exceeds the small but real cancer risk associated with the procedure. Therefore, fluoroscopy is used with the lowest possible exposure for the shortest possible time.