Patent US 4,286,157

A dosimeter for use in mammographs wherein a plate-like body of electrically non-conductive hard foamed material generates charge carriers in response to exposure to radiation. The body is provided with electrodes which are connected with an energy source. The output signal of the dosimeter is used to regulate the amounts of radiation to which an object is exposed. The entire dosimeter can be installed between the source of radiation and X-ray film or another carrier of images of objects because the dosimeter does not cast a shadow on the film when the object is exposed to radiation.