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A. M. Palmowski-Wolfe, C. Kober, I. Berg, C. Buitrago-Téllez, C. Kunz, E. W. Radü, S. Wetzel; Applying Computer Aided Visualization Techniques to Extra Ocular Muscle and Eye MRI. Invest. Ophthalmol. Vis. Sci. 2009;50(13):649.
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© ARVO (1962-2015); The Authors (2016-present)
At ARVO 2008 we had shown computer aided visualization techniques (CAVT) applied to oculodynamic MRIs of the orbit. Within the extra ocular muscles (EOM) a devision was seen that was discussed as possibly relating to the obital and the bulbar layer of the EOM. The purpose of this study is to further improve information on EOM structure and the eye in an integrated MRI-based approach.
A threefold strategy was followed. First, a post mortem MRI of a control subject was analyzed (1.5T, T1 weighted image sequence, 0.6mm layer thickness). 2nd, we analyzed a 1.5T MRI, done with the Gadolinium based contrast agent Dotarem®, that was obtained in a tumor patient for evaluation of his underlying disease. 3rd, the resulting images were compared to those of a living control (1.5 T) whose oculodynamic MRI movies we presented last year. To enhance visibility of the orbital structures, special adapted CAVT procedures based on direct volume rendering were applied to all MRI scans.
For all three approaches, the horizontal and vertical EOM could be clearly identified. Also, for all approaches, these EOM revealed a two layered structure, possibly related to the orbital and bulbar layer of the EOM, with some intermediate tissue in between. In the Dotarem ® MRI, contrast was enhanced in both the presumed ocular and the presumed bulbar layer of the EOM, but the intermediate zone was spared, indicating the absence of vascular structures. The enhanced contrast based on CAVT techniques facilitated identification of sclera, periorbita and muscular structures. Due to high resolution and image quality of the post mortem MRI, highly detailed 3D-reconstruction of the orbital anatomy was possible that allowed better visualization of the oblique muscles and virtual ‘turning’ of the eye in all directions. In addition, the lens including its attachment to the ciliary fibers could be shown.
Distribution of the contrast medium, Dotarem, in the EOM supports our previous thesis that 2 layers of the EOM can be shown. We postulate, that these relate to the orbital and the bulbar layer of the EOM. While 3D-reconstruction of the eye and its EOM could be greatly improved, differentiation within the connective tissue at the EOM muscle insertion to the sclera is still subject to future work.
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