Early Philips Mammography Tube

Ref. K3

Dating back to the early or mid-seventies, this oil-immersed glass-metal tube has a single 0.6 mm focal spot, fed by a six pulse generator, with an output of 25 to 50 kV and 200 mA. The tube has a Beryllium window and a rotating Molybdenum-faced anode disc, and is fitted with an additional Molybdenum filter. 

The metal part of the tube is made of an alloy which has the same heat expansion factor as glass. This alloy is most often made of iron, nickel and cobalt. It is usually known as “kovar”.

In the tube housing, there was a provision for water-cooling. The 200 mA power, and the water-cooling were necessary because initially non-screen mammography films came in light-tight paper envelopes, and needed long exposures. The Mammography screen-film technique came several years later.

Modern mammography tubes have two focal spots, generally 0.3 mm and 0.1 mm, an output generally of 100 mA, and are fed by a high frequency generator. Besides the molybdenum target, some tubes are also fitted with a Rhodium target and/or a Rhodium filter.