1. Field of the Invention
The present invention is directed to an x-ray diagnostics installation, and in particular to such an installation for mammography exposures.
2. Description of the Prior Art
X-ray installations for making mammography exposures are known which generating include an x-ray radiator, a support plate on which the mammary gland is exposed, and a computer for calculating the average parenchyma dose.
Knowledge of the exposure of the patient to radiation is needed in order to estimate the radiation risk. The dose quantity which is relevant for this purpose is the average parenchyma dose. The average parenchyma dose can be calculated by measuring the entry dose. Such a measurement, however, is usually not possible when preparing x-ray exposures with a patient, because a shadow-producing detector would have to be arranged in front of the exposure subject for this purpose.
For calculating the average parenchyma dose, it is disclosed in European Application 0 325 120 corresponding to U.S. Pat. No. 4,905,150, to employ a computer to which electrical signals are supplied corresponding to various exposure values. The computer calculates the average parenchyma dose from these values according to a given equation. An actual measurement of the average parenchyma dose, consequently, is not undertaken in this known apparatus.