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J.M. Miller, E.A. Rossi, S. Konishi, M.D. Abramoff; Visualizing Ocular Tissue Movement with Little Gold Beads . Invest. Ophthalmol. Vis. Sci. 2003;44(13):3123.
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Purpose: Visualize movement of ocular (and other) soft tissues that present no suitable intrinsic features. Methods: Under surgical anesthesia, we randomly injected several dozen tiny (0.1mm dia) gold beads into connective tissues, muscles, sclera and periosteum of monkeys trained to fixate light spots. After recovery, we collected conventional X-ray images with multiple views and gaze angles. The location in 3-space of each gold bead was found and tracked as a function of gaze, using techniques of multiple-view projective geometry. Results: Implantation is easily accomplished with a custom bead injector. Precise imaging during fixation is straightforward with conventional digital dental X-ray equipment. Beads remain stable in soft tissues for several months or longer. Two views are sufficient to reconstruct most bead locations without precise specification of x-ray source and sensor; three views resolve accidental occlusions. Differential movements of implanted tissues are easily visualized. Conclusions: An X-ray technique using injected gold bead fiducials is useful for visualizing extraocular muscle paths, muscle contraction and stretching, connective tissue movements, and eye rotation in alert animals. To objectively segment the optical flow we are developing a multiple layer mixture model which performs a maximum likelihood estimation of the "layers", thereby distinguishing distinct mechanical tissue elements. View OriginalDownload SlideView OriginalDownload Slide
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