The calculation of absorbed dose from exposure measurements: practical problems in dosimetry

At least two procedures for determination of dose within an irradiated medium from ionization chamber measurements are in common use. One involves a determination of exposure in air and the application of conversion factors. The second involves the introduction of the ion chamber directly into the medium and a determination of exposure at that point followed by the application of conversion factors. For each of these methods a small attenuation correction must be applied to the exposure determination. The correction is commonly applied to ionization measurements made directly in the medium but is almost universally ignored when the reference exposure determination is made in air.