Densitometric aspects of mammography

Exposure doses in mammography were determined with a special low-energy ionization chamber. The highest values between 400 and 2600 μC/kg resulted from non-screen films using molybdenum tubes and filters. By optimized film processing these doses can be reduced to 500-770 μC/kg. Characteristic for molybdenum tubes are the high doses in tissues near the surface. Already at 1 cm depth these values reduce to 10-40%, in the center of a 6 cm thick mamma they are 3-6% of the surface dose. For tubes with wolfram anodes surface doses are considerably lower. They were 80-230 μC/kg for non-screen films and 26-77 μC/kg in the center of a 6 cm thick mamma. With intensifying screens these doses can be reduced by a factor of 10 or more. (author)