Measuring skin dose rate or total accumulated dose to the skin alone is not enough to predict whether or not a patient will develop skin damage. If the dose was distributed over large areas of skin, then the chances of damage will be much less than if the same area was repeatedly exposed.
Dose Area Product (DAP), is a multiplication of the dose and the area exposed, often expressed in Gy.cm2. Modern x-ray systems are fitted with a DAP meter, able to record accumulated DAP during an examination.
Researchers have attempted to estimate effective dose and skin dose from DAP readings, but the predicted figures can only be a rough approximation. This is due to the fact that other factors are required for a more accurate estimate of effective dose or skin dose, such as the beam geometry with respect to the patient, kVp, and so on.
Despite these limitations, DAP is currently the most convenient method of monitoring patient doses.