Radiographic apparatus and methods.

摘要

In the apparatus an x-ray tube (A) is powered by a control circuit (C) for selectively irradlating a sheet of x-ray film (B). An operator selects the operating anode current mA for the x-ray tube, an exposure or dose value (preferably an mAs value), and a tube voltage kV on a keyboard (20). For a fixed operating voltage and selected mAs value, the film should be exposed to the same density regardless of whether a low mA and a long time or a high mA and a short time are selected. Particularly in single phase inverter control circuit and power supplies, the high current and short time exposures tend to be underdeveloped relative to low mA and long time exposures for the same mAs value. To standardize the exposure for any current and time combination of the selected mAs value, a look up table (60) is provided. The look up table is addressed by the selected kV, mA, and mAs values to retrieve an appropriate current boost value which boosts the actual current such that the film is exposed to the selected density. The current boost value is added (42) to the selected current such that the x-ray tube is operated or boosted above the selected anode current by the appropriate amount for the x-ray film to be exposed to the same density for all mA and time combinations corresponding to the same mAs value. Alternately, exposure time may be lengthened to achieve the correct dose.