Quantitative Assessment of Normal Fetal Brain Myelination Using Fast Macromolecular Proton Fraction Mapping

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Background: Apparent diffusion coefficient (ADC) is known as a quantitative biomarker of prenatal brain maturation. Fast macromolecular proton fraction (MPF) mapping is an emerging method for quantitative assessment of myelination that was recently adapted to fetal MRI. Purpose: To compare the capability of ADC and MPF to quantify the normal fetal brain development. Study Type: Prospective. Population: 42 human fetuses in utero (gestational age (GA) = 27.7 ± 6.0, range 20–38 weeks). Field Strength/Sequence: 1.5T; diffusion-weighted single-shot echo-planar spin-echo with five b-values for ADC mapping; spoiled multi-shot echo-planar gradient-echo with T1, proton density, and magnetization transfer contrast weightings for single-point MPF mapping. Assessment: Two operators measured ADC and MPF in the medulla, pons, cerebellum, thalamus, and frontal, occipital, and temporal cerebral white matter (WM). Statistical Tests: Mixed repeated-measures ANOVA with the factors of pregnancy trimester and brain structure; Pearson correlation coefficient (r); Hotelling-Williams test to compare strengths of correlations. Results: From 2nd to 3rd trimester, ADC significantly decreased in the thalamus and cerebellum (P<0.005). MPF significantly increased in the medulla, pons, thalamus, and cerebellum (P<0.005). Cerebral WM had significantly higher ADC and lower MPF compared to the medulla and pons in both trimesters. MPF (r range 0.83− 0.89, P<0.001) and ADC (r range −0.43 −0.75, P≤0.004) significantly correlated with GA and each other (r range −0.32 −0.60, P≤0.04) in the medulla, pons, thalamus, and cerebellum. No significant correlations and distinctions between regions and trimesters were observed for cerebral WM (P range 0.1–0.75). Correlations with GA were significantly stronger for MPF compared to ADC in the medulla, pons, and cerebellum (Hotelling-Williams test P<0.003) and similar in the thalamus. Structure-averaged MPF and ADC values strongly correlated (r=0.95, P<0.001). Data Conclusion: MPF and ADC demonstrated qualitatively similar but quantitatively different spatiotemporal patterns. MPF appeared more sensitive to changes in the brain structures with prenatal onset of myelination.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 95%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Direct comparison between apparent diffusion coefficient and macromolecular proton fraction as quantitative biomarkers of the human fetal brain maturation

Korostyshevskaya

Prihod'ko

Савелов

et al. 2019

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Scan–Rescan Repeatability and Impact of B₀ and B₁ Field Nonuniformity Corrections in Single‐Point Whole‐Brain Macromolecular Proton Fraction Mapping

Yarnykh

Kisel

Khodanovich

2019

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Background: Single-point macromolecular proton fraction (MPF) mapping is a recent quantitative MRI method for fast assessment of brain myelination. Information about reproducibility and sensitivity of MPF mapping to magnetic field non-uniformity is important for clinical applications.Purpose: To assess scan-rescan repeatability and a value of B 0 and B 1 field inhomogeneity corrections in single-point synthetic-reference MPF mapping.Study Type: Prospective.Population: 8 healthy adult volunteers underwent two scans with 11.5±2.3 months interval.Field Strength/Sequence: 3T; whole-brain 3D MPF mapping protocol included three spoiled gradient-echo sequences providing T 1 , proton density, and magnetization transfer contrasts with 1.25×1.25×1.25 mm 3 resolution and B 0 and B 1 mapping sequences.Assessment: MPF maps were reconstructed with B 0 and B 1 field non-uniformity correction, B 0 and B 1 only corrections, and without corrections. Mean MPF values were measured in automatically segmented white matter (WM) and gray matter (GM).Statistical Tests: Within-subject coefficient of variation (CV), intraclass correlation coefficient (ICC), Bland-Altman plots, and paired t-tests to assess scan-rescan repeatability. Repeatedmeasures ANOVA to compare field corrections.Results: Maximal relative local MPF errors without correction in the areas of largest field nonuniformities were about 5% and 27% for B 0 and B 1 , respectively. Effect of B 0 correction was insignificant for whole-brain WM (P>0.25) and GM (P>0.98) MPF. The absence of B 1 correction caused a positive relative bias of 4-5% (P<0.001) in both tissues. Scan-rescan agreement was similar for all field correction options with ICCs 0.80-0.81 for WM and 0.89-0.92 for GM. CVs were 1.6-1.7% for WM and 0.7-1.0% for GM.

Preliminary Study on Quantitative Assessment of the Fetal Brain Using MOLLI T1 Mapping Sequence

Jia

Liao

et al. 2022

Background Prenatal quantitative evaluation of myelin is important. However, few techniques are suitable for the quantitative evaluation of fetal myelination. Purpose To optimize a modified Look–Locker inversion recovery (MOLLI) T1 mapping sequence for fetal brain development study. Study Type Prospective observational preliminary cohort study. Population A total of 71 women with normal fetuses divided into mid‐pregnancy (gestational age 24–28 weeks, N = 25) and late pregnancy (gestational age > 28 weeks, N = 46) groups. Field Strength/Sequence A 3 T/MOLLI sequence. Assessment T1 values were measured in pedunculus cerebri, basal ganglia, thalamus, posterior limb of the internal capsule, temporal white matter, occipital white matter, frontal white matter, and parietal white matter by two radiologists (11 and 16 years of experience, respectively). Statistical Tests The Kruskal–Wallis test was used for reginal comparison. For each region of interest (ROI), differences in T1 values between the mid and late pregnancy groups were assessed by the Mann Whitney U test. Pearson correlation coefficients (r) were used to evaluate the correlations between T1 values and gestational age for each ROI. Intraobserver and interobserver agreement was determined by the intraclass correlation coefficient (ICC). A P value <0.05 was considered statistically significant. Results Interobserver and intraobserver agreements of T1 were good for all ROIs (all ICCs > 0.700). There were significant differences in T1 values between lobal white matter and deep regions, respectively. Significant T1 values differences were found between middle and late pregnancy groups in pedunculus cerebri, basal ganglion, thalamus, posterior limb of the internal capsule, temporal, and occipital white matter. The T1 values showed significantly negative correlations with gestational weeks in pedunculus cerebri (r = −0.80), basal ganglion (r = −0.60), thalamus (r = −0.68), and posterior limb of the internal capsule (r = −0.77). Data Conclusion The T1 values of fetal brain may be assessed using the MOLLI sequence and may reflect the myelination. Evidence Level 3 Technical Efficacy Stage 2