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Preventing unnecessary exposure in radiography

» Can I reduce the radiation exposure to my patients by using low kV values?

No. 

In general reducing the kV would increase patient exposure. When the kV is reduced in radiography, both the output exposure of the X-ray tube and the penetration of the radiation through the patient are reduced. This requires an increase in the tube loading, PIt (in units of mAs) to obtain the same film exposure. This results in an increase in patient exposure.

The appropriate action is to select a kV value for a specific clinical procedure that provides the appropriate balance of image contrast and patient exposure. Established technique charts should be used to determine the optimum kV value for each procedure. Radiographers need to have the training and experience to evaluate patient thickness and other conditions to be considered in the selection of the appropriate kV values.

» How can I prevent unnecessary exposure to patients in digital radiography?

One of the characteristics of digital radiography, the wide dynamic exposure range of digital radiographic receptors, can cause unnecessary patient exposure. This is the characteristic that makes it possible to produce images that ‘look good’ and have appropriate contrast with a wide range of exposures. This is less of a problem with film radiography because over-exposure produces a dark film. However, an overexposed digital radiograph looks good and will not be recognized as one made with unnecessary exposure.

The appropriate action in digital radiography is to monitor the exposure used for each imaging procedure by observing the exposure index or other exposure indicator and train the staff to use appropriate exposure technique factors for each examination.