Reconfigurable x-ray aec compensation

Abstract

An automatic x-ray exposure time control wherein compensation curves representative of plots and reference signal voltages versus integrated x-ray dose signals can be reconfigured to account for the variable effects on x-ray film density resulting from the specific image receptor, collimator field area, x-ray intensity sensor and density factor used in any x-ray exposure technique over a range of operator-selected x-ray tube kilovoltage (kV) and current (mA). Data for a relatively small number of basic compensation curves are obtained and stored in ROMs. These curves are plots of exposure times versus integrated x-ray dose signals which resulted in producing a constant predetermined and desired film density for whatever amount of x-ray attenuating material is in the x-ray beam. Each basic curve is obtained with the x-ray tube operating at a particular kV and mA. Gain factors are developed in accordance with the respective image receptor, x-ray sensor, collimator setting and density factor used during an actual patient exposure. A basic compensation curve is called up in response to the user selecting a tube kV and mA. The ordinates of the basic curve are multiplied by the gain factors. The results are acted on by an algorithm that yields a corrected compensation curve and the data are put in a memory device in the form of binary representations of reference voltages versus exposure times. During an exposure the reference voltages are clocked out in time sequence and compared with the integrated dosage signal. When a comparison is made, the exposure is caused to terminate.