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.