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Abstract

A method for increasing the efficiency of gas ionization detectors for diagnostic x-rays by matching a detector gas absorption edge with the energy level of an x-ray source to produce photons of only slightly higher energy. Sequential x-ray images using different matched gas absorption edges and x-ray source energies allows contrast information to be obtained to distinguish calcium deposits or dye from bone, for example. Specific ionization detectors useful for practicing the inventive methods are also described. One such detector uses ultrafast electronics associated with individual wires of a multiwire two dimensional proportional counter. Another detector employs a conductor backed sheet of insulating material to immobilize positive gas ions in a density distribution conforming to the x-ray image. The density distribution may subsequently be read out by electromechanical means for sensing the potential differences on the sheet. The potential sensing means may be located within or outside the detector chamber.

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First Claim