<title>Digital stereomammography: observer performance study of the effects of magnification and zooming on depth perception</title>

Abstract

We have previously reported the effects of stereo angle and exposure on depth discrimination and the use of virtual cursors for absolute depth measurements in digital stereomammography. The current study further investigates the effects of magnification and zooming on depth perception. Stereoscopic image pairs of a phantom were acquired with a full-field digital mammography system. The modular phantom contained 25 crossing fibril pairs with depth separations between each pair ranging from 2 to 10 mm. Three phantom (fibril) configurations were imaged using techniques of 30 kVp, Rh/Rh, +/- 3 degrees stereo angle, , contact and 1.8X magnification geometry, and 4 to 63 mAs exposure range. The images were displayed on a Barco monitor driven by a Metheus stereo graphics board and viewed with LCD stereo glasses. Five observers participated in the study. Each observer visually judged if the vertical fibril was in front of or behind the horizontal fibril in each pair. It was found that the accuracy of depth discrimination increased with increasing fibril depth separation and x-ray exposure. Zooming the contact stereo images by 2X did not improve the accuracy. Under conditions of high noise (low mAs) and small depth separation between the fibrils, depth discriminations were significantly better in stereo images acquired with geometric magnification than in images acquired with a contact technique and displayed with or without zooming. This study indicates that stereoscopic imaging, especially with magnification, may be useful for visualizing the spatial distribution of microcalcifications in a cluster and differentiating overlapping tissues from masses on mammograms.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.