Human subject images with an active dual-energy computed radiography system and comparison with a commercial `sandwich' detector system

We have developed a new detector for dual energy computed radiography that uses fast switching of the x-ray tube voltage. Voltage switching gives x-ray spectra with wider separation and lower average energy than conventional `sandwich' detectors. When properly optimized, these better-conditioned spectra produce dual energy images with lower noise for the same dose. We constructed a prototype of the detector, optimized it, and used it to produce human subject images of ten human volunteers. We also compared the performance of the active detector with a commercial dual-energy, computed radiography system that uses a sandwich detector. The results are as follows: We were able to produce high quality images for all ten volunteers. There were slight artifacts at the edge of the heart in some of the images but these did not affect their diagnostic utility. The active detector required approximately 1/4 the entrance exposure of the commercial, dual-energy system to produce diagnostic quality images of an anthropomorphic chest phantom. A substantial decrease in radiation exposure can be obtained with the dual-energy active detector approach with a modest increase in the complexity of the acquisition equipment.