Monochromatic imaging with a conventional source using polycapillary x-ray optics

Monochromatic parallel beam imaging produces high subject contrast, high resolution, and low patient dose. Polycapillary collimating optics can be used to create a beam of sufficient intensity for monochromatization from a conventional source. Monochromatization is achieved by diffraction from a single crystal. Contrast, resolution, and intensity measurements were performed with both high and low angular acceptance crystals. Testing was first done at 8 keV with an intense copper rotating anode, then preliminary 17.5 keV measurements were made with a low power molybdenum source. At 8 keV, contrast enhancement was a factor of 5 relative to the polychromatic case, in good agreement with theoretical values. At 17.5 keV, monochromatic subject contrast is a factor of 2 times greater than the conventional polychromatic contrast. An additional factor of two increase in contrast is expected from the removal of scatter obtained from using the air gap which is allowable from the parallel beam. The measured angular resolution after the crystal was 0.6 mrad for a silicon crystal. The use of polycapillary collimating optics allowed monochromatic imaging measurements using a conventional rotating anode source and computed radiography plate in 300 mAs.