Methods and device related to automatic exposure in X-ray diagnostics in particular in mammography

Claim 1

Method in X-ray diagnostics, and particular in mammography, for regulation of the exposure of an image receptor (F) to an optimal level, wherein the radiation that has passed through an object (2) of photography and through the image receptor is measured by means of an arrangement of detectors (4a . . . 4n) operative to produce measurement signals and, based on this measurement, the time of exposure or equivalent is adjusted, characterized by the steps of: initially calibrating the detectors, amplifiers (5a . . . 5n) associated with the detectors, and an integrator (6) by first zeroing the integrator and then exposing a reference object to a predetermined dosage of X-ray radiation to produce measurement signals from one or more of the detectors, one at a time; passing the measurement signals from the detectors to the associated amplifiers to obtain an amplified measurement signal for each amplifier; passing the amplified signals from each amplifier one at a time to the integrator, set to an initial integration switching period and zeroed between the measurements, to integrate the amplified measurement signals from each amplifier; comparing the amplified and integrated measurement signals with a predetermined reference value and independently adjusting the switching period of each amplified signal being integrated to produce adjusted amplification values independently for each detector and its associated amplifier, so that at the predetermined dosage, each detector and amplifier gives an integrated measurement signal equal to the predetermined reference value; and thereafter exposing an unknown object to a dosage of X-ray radiation to produce measurement signals from the detectors; automatically adjusting the switching period for the amplified signals from each detector and its associated amplifier by means of a control system in response to the adjusted amplification value obtained during the initial integration, as the amplified measurement signals for the unknown object are passed from the detectors to the amplifiers and to the integrator, so that the integrated result is a predetermined function of the amplified detector signals based on the adjusted amplification values determined during the calibration; and discontinuing the dosage of radiation to the unknown object when the integrated measurement signals reach a predetermined target value selected to be the intended dosage for the unknown object.