Scan-rescan reproducibility and interobserver reliability of T1 and T2 measurements of extraocular muscles using a multi-dynamic multi-echo MRI sequence

Quantitative assessment of extraocular muscles (EOMs) is crucial for the clinical management of thyroid-associated ophthalmopathy, 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 was to evaluate the scan-rescan reproducibility and interobserver reliability of T1 and T2 quantification in the EOMs using MDME sequence. 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 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. Nineteen subjects (mean age 40.3 ± 10.5 years) were finally analyzed. The median scan-rescan interval was 9 days [interquartile range (IQR), 7–14]. Scan-rescan reproducibility was good for T1 value (first scan: 933.4 [892.5–1102.5] ms, second scan: 956.4 [856.7–1069.9] ms, ICC = 0.694, bias = 28.1 ms, CV = 8.47%) and moderate for T2 value (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 ≤ 2.05%). The MDME sequence enables rapid and reproducible T1 and T2 quantification of EOMs with excellent interobserver reliability, demonstrating promising potential as a practical and feasible routine tool for quantitative assessment of orbital disorders, particularly thyroid-associated ophthalmopathy. Not applicable.