As part of an ongoing study that uses objective image quality measures to optimize medical imaging x-ray fluoroscopy, we investigated two basic features of the detection of moving cylinders that mimic arteries, catheters, and guide wires. First, we compared detection with and without a phase cue consisting of a nearby alternating light and dark square. Depending on object size and velocity, phase cuing improved detection from 1% to 15% and gave an average of 6%, an effect much smaller than the 38% predicted from a Monte Carlo simulation of the ideal observer. Evidently, humans were limited in their ability to incorporate knowledge of the phase cue. Second, we evaluated the effect of eye pursuit of a fixation point that moved with the target. In general, motion at the highest velocity degraded (74%) and enhanced (68%) detection of small and large objects, respectively. With eye pursuit, both effects were substantially reduced in a manner consistent with a reduced retinal velocity. Our data compared favorably with a human observer model that included a spatiotemporal contrast sensitivity response and smooth-pursuit eye movements with a gain of 0.8. These mechanisms of perception are thought to be present in coronary artery x-ray fluoroscopy imaging, where phase information is available from the moving heart and where motion markers are available from x-ray opaque markers incorporated in thin catheters and guide wires.
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