Detectability of depth information by use of magnification stereoscopic technique in cerebral angiography.

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Abstract
Two types of stereoscopic phantoms were constructed to determine the sensitivity of observers in detecting depth information obtained by means of the magnification stereoscopic technique. One of these, a plus phantom, contained perpendicular aluminum wires at the top and bottom of steps of various thicknesses; the observer was asked to identify whether one of the wires was on the top, the bottom or uncertain in location. The fraction of correct responses vs. the height of the step was plotted, indicating the detectability of depth. Of 20 unselected observers, 14 (70%) responded consistently and were considered good observers. In general, the greater the stereo shift, the greater the fraction of correct responses. A 2nd phantom, a mesh phantom, contained standard and randomly positioned test wires. The observer was asked to identify the depth position of a test wire with respect to the standard wire if they were in the same plane. Observers can discriminate depth differences of 1-2 mm in magnification stereoscopy, and similar performance for magnification stereoscopic cerebral angiograms is expected.