- Dose area product
Dose area product (DAP) is a quantity used in assessing the radiation risk from diagnostic X-rays examination and interventional procedures. It reflects not only the dose within the radiation field but also the area of tissue irradiated. Therefore, it may be a better indicator of the overall risk of inducing cancer than the dose within the field. It also has the advantages of being easily measured, with the permanent installation of a DAP meter on the X-ray set. DAP is expressed in Gray square centimetres (Gy*cm²) (sometimes mGy*cm² or cGy*cm²). Manufacturers of DAP meters usually calibrate them in terms of absorbed dose to air.
Kerma area product (KAP) is a related quantity which for all practical radiation protection purposes is equal to dose area product. However, strictly speaking DAP = KAP x (1-g) where g is the fraction of energy of liberated charged particles that is lost in radiative processes in the material, and the dose is expressed in absorbed dose to air. The value of g for diagnostic X-rays is only a fraction of a percent.
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