T2 mapping of the extraocular muscles in healthy volunteers: preliminary research on scan-rescan and observer-observer reproducibility.

BACKGROUND: T2-mapping technique and derived T2 relaxation time allows quantitative assessment of extraocular muscles; however, the reproducibility of T2 mapping-derived parameters was seldom studied till now.
PURPOSE: To evaluate the scan-rescan and observer-observer reproducibility of T2 relaxation time measurements of extraocular muscles in young healthy volunteers.
MATERIAL AND METHODS: Fourteen volunteers underwent T2-mapping examinations of the extraocular muscles three times within one month on a 3.0-T MR system. Scan-rescan and observer-observer reproducibility of T2 relaxation time measurements of the extraocular muscles were assessed using intraclass correlation coefficient and coefficient of variation.
RESULTS: Both scan-rescan (short-term and long-term) and observer-observer could achieve good to excellent reproducibility, while better short-term than long-term scan-rescan reproducibility was obtained. The coefficient of variation of the T2 relaxation time of each extraocular muscles during both scan-rescan and observer-observer reproducibility assessment were <6%.
CONCLUSION: T2 relaxation time measurement of the extraocular muscles is proven to be highly reproducible at 3.0 T. T2 mapping may be a potential imaging technique in the diagnosis and follow-up of orbital diseases involved extraocular muscles in further studies.