Validity of SyMRI for Assessment of the Neonatal Brain

Yildirim

et al. 2022

BACKGROUND AND PURPOSE: Former preterm born males are at higher risk for neurodevelopmental disabilities compared with female infants born at the same gestational age. This retrospective study investigated sex-related differences in the maturity of early myelinating brain regions in infants born ,28 weeks' gestational age using diffusion tensor-and relaxometry-based MR imaging. MATERIALS AND METHODS:Quantitative MR imaging sequence acquisitions were analyzed in a sample of 35 extremely preterm neonates imaged at term-equivalent ages. Quantitative MR imaging metrics (fractional anisotropy; ADC [10 À3 mm 2 /s]; and T1-/T2relaxation times [ms]) of the medulla oblongata, pontine tegmentum, midbrain, and the right/left posterior limbs of the internal capsule were determined on diffusion tensor-and multidynamic, multiecho sequence-based imaging data. ANCOVA and a paired t test were used to compare female and male infants and to detect hemispheric developmental asymmetries. RESULTS:Seventeen female (mean gestational age at birth: 26 1 0 [SD, 1 1 4] weeks1days) and 18 male (mean gestational age at birth: 26 1 1 [SD, 1 1 3] weeks1days) infants were enrolled in this study. Significant differences were observed in the T2-relaxation time (P ¼ .014) of the pontine tegmentum, T1-relaxation time (P ¼ .011)/T2-relaxation time (P ¼ .024) of the midbrain, and T1-relaxation time (P ¼ .032) of the left posterior limb of the internal capsule. In both sexes, fractional anisotropy (P [$] , .001/P [#] , .001) and ADC (P [$] ¼ .017/P [#] ¼ .028) differed significantly between the right and left posterior limbs of the internal capsule. CONCLUSIONS:The combined use of various quantitative MR imaging metrics detects sex-related and interhemispheric differences of WM maturity. The brainstem and the left posterior limb of the internal capsule of male preterm neonates are more immature compared with those of female infants at term-equivalent ages. Sex differences in WM maturation need further attention for the personalization of neonatal brain imaging.

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confidence: 99%

Different from the Beginning: WM Maturity of Female and Male Extremely Preterm Neonates—A Quantitative MRI Study

Yildirim

et al. 2022

“…1 Recent advances in synthetic imaging provide multiple contrasts (ie, TR, TE, and TI are synthetically defined in retrospect) based on the tissue-specific properties (ie, relaxation time and spin density) determined via a single multidynamic multiecho (MDME) sequence. 8,[11][12][13][14][15][16] Novel inversion recovery acquisition strategies (ie, fast gray matter acquisition T1 inversion recovery [FGATIR]) use a short TI to suppress the myelin signal, therefore improving discrimination of brainstem pathways and identification of myelinated tissue. 17 While this approach has proved beneficial primarily in a neurosurgical imaging setting, there is a lack of information on the applicability of such contrasts for the assessment of neonatal brain myelination.…”

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confidence: 99%

Synthetic MR Imaging–Based WM Signal Suppression Identifies Neonatal Brainstem Pathways in Vivo

Yildirim

et al. 2022

BACKGROUND AND PURPOSE: Multidynamic multiecho sequence-based imaging enables investigators to reconstruct multiple MR imaging contrasts on the basis of a single scan. This study investigated the feasibility of synthetic MRI-based WM signal suppression (syWMSS), a synthetic inversion recovery approach in which a short TI suppresses myelin-related signals, for the identification of early myelinating brainstem pathways.MATERIALS AND METHODS: Thirty-one cases of neonatal MR imaging, which included multidynamic multiecho data and conventionally acquired T1-and T2-weighted sequences, were analyzed. The multidynamic multiecho postprocessing software SyMRI was used to generate syWMSS data (TR/TE/TI ¼ 3000/5/410 ms). Two raters discriminated early myelinating brainstem pathways (decussation of the superior cerebellar peduncle, medial lemniscus, central tegmental tract, and medial longitudinal fascicle [the latter 3 assessed at the level of the pons]) on syWMSS data and reference standard contrasts. RESULTS: On the basis of syWMSS data, the decussation of the superior cerebellar peduncle (31/31); left/right medial lemniscus (31/ 31; 30/31); left/right central tegmental tract (19/31; 20/31); and left/right medial longitudinal fascicle (30/31) were reliably identified by both raters. On the basis of T1-weighted contrasts, the decussation of the superior cerebellar peduncle (14/31); left/right medial lemniscus (22/31; 16/31); left/right central tegmental tract (1/31); and left/right medial longitudinal fascicle (9/31; 8/31) were reliably identified by both raters. On the basis of T2-weighted contrasts, the decussation of the superior cerebellar peduncle (28/31); left/ right medial lemniscus (16/31; 12/31); left/right central tegmental tract (23/31; 18/31); and left/right medial longitudinal fascicle (15/31; 14/31) were reliably identified by both raters.CONCLUSIONS: syWMSS data provide a feasible imaging technique with which to study early myelinating brainstem pathways. MR imaging approaches that use myelin signal suppression contribute to a more sensitive assessment of myelination patterns at early stages of cerebral development.

“…Because the image postprocessing is performed in less than 1 minute, SyMRI provides qualitative as well as quantitative MR data in a clinically acceptable time. [21][22][23] In neonates, the process of myelination leads to subtle MR signal changes because of alterations in relaxation parameters and spin density, detectable by quantitative MR techniques. The aim of this study was to investigate the impact of different stages of prematurity on the maturational characteristics of the neonatal brain stem, as measured by SyMRI-based T1, T2, and PD mapping.…”

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confidence: 99%

Impact of Prematurity on the Tissue Properties of the Neonatal Brain Stem: A Quantitative MR Approach

Geisl

et al. 2021

BACKGROUND AND PURPOSE: Preterm birth interferes with regular brain development. The aim of this study was to investigate the impact of prematurity on the physical tissue properties of the neonatal brain stem using a quantitative MR imaging approach. MATERIALS AND METHODS:A total of 55 neonates (extremely preterm [n ¼ 30]: ,28 1 0 weeks gestational age; preterm [n ¼ 10]: 28 1 0-36 1 6 weeks gestational age; term [n ¼ 15]: $37 1 0 weeks gestational age) were included in this retrospective study. In most cases, imaging was performed at approximately term-equivalent age using a standard MR protocol. MR data postprocessing software SyMRI was used to perform multidynamic multiecho sequence (acquisition time: 5 minutes, 24 seconds)-based MR postprocessing to determine T1 relaxation time, T2 relaxation time, and proton density. Mixed-model ANCOVA (covariate: gestational age at MR imaging) and the post hoc Bonferroni test were used to compare the groups.RESULTS: There were significant differences between premature and term infants for T1 relaxation time (midbrain: P , .001; pons: P , .001; basis pontis: P ¼ .005; tegmentum pontis: P , .001; medulla oblongata: P , .001), T2 relaxation time (midbrain: P , .001; tegmentum pontis: P , .001), and proton density (tegmentum pontis: P ¼ .004). The post hoc Bonferroni test revealed that T1 relaxation time/T2 relaxation time in the midbrain differed significantly between extremely preterm and preterm (T1 relaxation time: P , .001/ T2 relaxation time: P ¼ .02), extremely preterm and term (T1 relaxation time/T2 relaxation time: P , .001), and preterm and term infants (T1 relaxation time: P , .001/T2 relaxation time: P ¼ .006). CONCLUSIONS:Quantitative MR parameters allow preterm and term neonates to be differentiated. T1 and T2 relaxation time metrics of the midbrain allow differentiation between the different stages of prematurity. SyMRI allows for a quantitative assessment of incomplete brain maturation by providing tissue-specific properties while not exceeding a clinically acceptable imaging time.