Fluoroscopy is the method that provides real-time X ray imaging. The ability of fluoroscopy to display motion is provided by a continuous series of images produced at a maximum rate of 25-30 complete images per second. This is similar to the way conventional television or video transmits images.


While the X ray exposure needed to produce one fluoroscopic image is low (compared to radiography), high exposures to patients can result from the large series of images that are encountered in fluoroscopic procedures. Therefore, the total fluoroscopic time is one of the major factors that determines the exposure to the patient from fluoroscopy.

Because the X ray beam is usually moved over different areas of the body during a procedure, there are two very different aspects that must be considered. One is the area most exposed by the beam, which results in the highest absorbed dose to that specific part of the skin and to specific organs. The other is the total radiation energy imparted to the patient’s body, which is related to the Kerma Area Product (KAP or PAK), a quantity that is easily measurable.

The absorbed dose to a specific part of the skin and other tissues is of concern in fluoroscopy for two reasons: one is the need for minimizing the dose to sensitive organs, such as the gonads and breast, by careful positioning of the X ray beam and using shielding when appropriate. The second is the possible incidence of the radiation beam to an area of the skin for a long time that can result in radiation injuries in cases of very high exposure.

On the other hand, the total radiation energy imparted to the patient’s body during a procedure is closely related to the effective dose and to the risk of radiation induced cancer.

In fluoroscopy, as in all types of X ray imaging, the minimum exposure required to form an image depends on the specific image information requirements.An important characteristic of a fluoroscopic system is its sensitivity, i.e. the amount of exposure required to produce images. The use of intensifier tubes and more modern digital flat panel receptors make it possible to optimize the balance of patient exposure with image quality so as not to expose the patient to unnecessary radiation. Non-intensified fluoroscopy with just a fluorescent screen for a receptor should not be used because of the excessive exposure to the patient.