Mean glandular dose

MGD can be calculated from a measured incident air kerma at the top of the breast, ${\displaystyle K}$, as follows:^[4]

${\displaystyle D=Kgcs}$

${\displaystyle g}$ converts from incident air kerma to MGD, with a glandularity of 50%, based on breast thickness and HVL. ${\displaystyle c}$ corrects for glandularity other than 50%, depending on the breast thickness and HVL, with two versions for ages 50–64 and 40–49. ${\displaystyle s}$ corrects for the x-ray spectra in use with a table of target/filter combinations.^[4][5]

MGD is typically used to define limits on mammography exposures by national and international organisations such as the European Union and International Atomic Energy Agency, at <2.5 milligray (mGy) per exposure to a standard breast (4.5 cm PMMA).^[6]

In routine quality assurance testing of mammographic equipment, MGD measurements for a range of effective breast thicknesses with PMMA, and from real patient exposures, is widely recommended.^[2]