Dual voltage X-ray examination technique - involves alternately running tube at low and high voltage to optimise contrast

摘要

The low voltage is chosen to give optimum contrast of the soft parts of the patient's body, whill the high voltage gives optimum contrast when reproducing the bones. The relative proportions of hard and soft X-rays in the exposure are adjusted by varying the times at the two voltage levels, the tube voltage being modulated as a rectangular wave over the entire explosure time. The X-ray pictures are displayed on the screen of a television type cathode ray tube. The signals from the X-ray picture screen pass through two different amplifiers which are switched in depending on which voltage is being applied to the X-ray tube.