Enhancement pattern of normal extraocular muscles in dynamic contrast-enhanced MR imaging with fat suppression

Purpose. To evaluate the internal structure of normal extraocular muscles o n fat-suppressed dynamic contrast-enhanced MR imaging. Material and Methods. Ten subjects were examined using fat-suppressed dynam ic contrast-enhanced MR imaging. We evaluated the enhancement pattern (C-sh aped or ring-like) of extraocular muscles and quantified the maximum ratios of enhancement (R-max) and maximum ratios of signal increase (V-max). We a lso quantified R-max and V-max in the central and peripheral portions of me dial rectus muscles. Results: in the early phase of dynamic contrast-enhanced MR imaging, a C-sh aped or ring-like pattern was observed in 100% of inferior rectus, 95% of m edial rectus, 55% of superior rectus, 20% of lateral rectus, and 15% of sup erior oblique muscles. Overall mean R-max and V-max values showed statistic ally significant differences to the temporal muscles. For the peripheral po rtion of medial rectus muscles, mean R-max and V-max values were greater th an for the central portion. Conclusion: Using fat-suppressed dynamic contrast-enhanced MR imaging, the C-shape or ring-like internal structure of the extraocular muscles could be visualized, and were considered to reflect their structure of orbital and global layers. Potential usefulness of the fat-suppressed dynamic contrast- enhanced MR imaging for detecting pathological status is suggested.