High‐Fidelity T2 Relaxometry of the Developing Fetal Brain Using an 8‐Second Single‐Shot Multiple Overlapping‐Echo Detachment ( MOLED ) MRI Technique

ABSTRACT Background Although quantitative MRI can provide objective biomarkers for brain maturation assessment, unpredictable fetal movement limits its application on fetuses. Purpose To evaluate single‐shot multiple overlapping‐echo detachment ( MOLED ) imaging for fetal brain T2 relaxometry and to quantify fetal brain maturation using T2 relaxation time. Study Type Phantom and prospective in vivo assessment. Subjects T2 phantom and 52 fetuses (mean gestational age [GA], 30.94 ± 3.62 weeks; range, 23–37 weeks). Field Strength/Sequence 3T; half‐Fourier acquisition single‐shot turbo spin‐echo (HASTE) and MOLED sequences. Assessment The accuracy, motion robustness, and repeatability of 8‐s MOLED T2 relaxometry were assessed using motion‐free and motion phantom acquisitions. In 15 fetuses, the MOLED scan was repeated within 5 min to assess scan‐rescan repeatability. Regional T2 values were determined in fetal white matter (WM), deep gray matter (dGM) and brainstem, and their changes with GA evaluated. Statistical Tests Bland–Altman analysis, linear regression analysis (Pearson correlation coefficient, r ), coefficient of variation, repeated‐measures analysis of variance, and intraclass correlation coefficient. p < 0.05 was considered statistically significant. Results Motion‐free and motion phantom acquisitions demonstrated that MOLED T2 significantly agreed with reference T2 ( r = 0.99). In vivo studies reported mean T2 values for all fetuses ( WM , 215.20 ms; dGM , 145.82 ms; brainstem, 125.80 ms). Scan–rescan acquisitions showed non‐significant mean T2 differences (bias < 1%; limits of agreement, −8.51% to +7.78%). Regional T2 values showed significant negative correlations ( r , −0.85 to −0.60) with GA . The brainstem exhibited a significantly higher rate of GA ‐related T2 change (3.43 ms per week) than WM and dGM (2.19 and 2.89 ms per week, respectively). Data Conclusion MOLED imaging appears to allow motion‐robust, clinically feasible, and highly repeatable T2 measurements for the whole fetal brain in 8 s. Regional differences in T2 values and age‐related T2 changes demonstrate its potential for quantifying in utero brain maturation. Evidence Level 2. Technical Efficacy Stage 1.