Air-kerma, product

The product of incident air kerma [math]K_i,[/math] and area [math]A[/math] of the x-ray beam in a plane perpendicular to the beam axis provides information on the extent of the x-ray beam. The common unit for air kerma–area product is [math]Gycm^2[/math]. The PKA has the useful property of being approximately invariant with distance from the x-ray tube focal spot. It can be measured in any plane between the x-ray source and the patient using specially designed transparent ionising chambers mounted at the collimator system or, in digital systems, calculated using data of the generator and the digitally recorded jaw position. The air kerma–area product is the recommended quantity to establish diagnostic reference levels in radiography and complex procedures including fluoroscopy. It is helpful in dose control for stochastic effects to patients and operators. (Adapted from ICRP Publication 117, 2010)

ICRP Glossary entry - May 2019