Scan and Rescan Reproducibility of T1/T2 Measurements Using Multi-dynamic Multi-echo Sequence in Extraocular Muscle MRI

Background Quantitative assessment of extraocular muscle (EOM) is crucial for the clinical management of thyroid-associated ophthalmopathy (TAO) and other orbital disorders. The multi-dynamic multi-echo (MDME) sequence is a synthetic MRI technique acquiring 2D multi-echo images via turbo spin echo or a combination of gradient echo and spin echo methods. The aim of this study is to evaluate the scan-rescan reproducibility and interobserver reliability of T1 and T2 quantification in the extraocular muscles (EOMs) using MDME sequence. Methods In this prospective study, twenty-two healthy volunteers underwent two MDME scans (interval 7-14 days) on a 3T MRI system with a 20-channel head-neck coil. Quantitative T1 and T2 maps were generated using post-processing software. Two observers independently outlined regions-of-interest (ROIs) within the EOMs to extract T1 and T2 relaxation times. Intraclass correlation coefficient (ICC), coefficient of variation (CV), and Bland-Altman analyses were employed to assess reproducibility and agreement. Results Nineteen subjects (mean age 40.3 ± 10.5 years) were finally analyzed. The median interscan interval was 9 days [interquartile range, 7–14]. Scan-rescan reproducibility was good for both T1 (first scan: 933.4 [892.5–1102.5] ms, second scan: 956.4 [856.7–1069.9] ms, ICC = 0.694, bias = 25.1 ms, CV = 8.47%) and T2 values (first scan: 91.1 [86.5–99.7] ms, second scan: 97.2 [89.5–108.5] ms, ICC = 0.587, bias = –3.5 ms, CV = 8.42%). Interobserver agreement was excellent (T1: ICC ≥ 0.968, absolute bias ≤ 11.4 ms, CV ≤ 1.92%; T2: ICC ≥ 0.927, absolute bias ≤ 1.3 ms, CV ≤ 1.72%). Conclusion The MDME sequence enables rapid and reproducible T1 and T2 quantification of EOMs with excellent interobserver reliability, demonstrating strong potential as an efficient and standardized tool for quantitative assessment of orbital disorders, particularly thyroid-associated ophthalmopathy. Clinical trial number Not applicable