HIGH CONTRAST IMAGING WITH POLYCAPILLARY OPTICS

摘要

Magnifying polycapillary X-ray optics provide an innovative new way to control X-rayrnbeams. The optics have measured primary transmissions greater than 50% and scatterrntransmission less than 1%. Contrast enhancement was nearly a factor of two compared to arnconventional grid as measured using 5-cm thick Lucite phantoms.rnAlternatively, using a collimating optic and diffracting crystal provides sufficientrnmonochromatic beam intensity for medical imaging. Contrast, resolution, and intensityrnmeasurements were performed with both high and low angular acceptance crystals. At 8 keV,rncontrast enhancement was a factor of 5 relative to the polychromatic case, in good agreementrnwith theoretical values. At 17.5 keV, monochromatic subject contrast was more than a factorrnof 2 times greater than the conventional polychromatic contrast. An additional factor of twornincrease in contrast is expected from the removal of scatter obtained by using an air gaprnwhich is made possible with a parallel beam. The measured angular resolution after therncrystal was 0.4 mrad for a silicon crystal.