Comparison of spin-echo and gradient-echo T1-weighted and spin-echo T2-weighted images at 3T in evaluating term-neonatal myelination

Imaging Findings and MRI Patterns in a Cohort of 18q Chromosomal Abnormalities

BACKGROUND AND PURPOSE

The abnormalities of the long arm of chromosome 18 (18q) constitute a complex spectrum. We aimed to systematically analyze their MR imaging features. We hypothesized that there would be variable but recognizable white matter and structural patterns in this cohort.

MATERIALS AND METHODS

In this retrospective cohort study, we included pediatric patients with a proved abnormality of 18q between 2000-2022. An age- and sex-matched control cohort was also constructed.

RESULTS

Thirty-six cases, median MR imaging age 19.6 months (4.3-59.3), satisfied our inclusion criteria. Most were female (25, 69%, F:M ratio 2.2:1). Fifty MR imaging studies were analyzed, and 35 (70%) had delayed myelination. Two independent readers scored brain myelination with excellent interrater reliability. Three recognizable evolving MR imaging patterns with distinct age distributions and improving myelination scores were identified: Pelizaeus-Merzbacher disease-like (9.9 months, 37), intermediate (22 months, 48), and washed-out pattern (113.6 months, 53). Etiologically, MRIs were analyzed across 3 subgroups: 18q deletion (34, 69%), trisomy 18 (10, 21%), and ring chromosome 18 (5, 10%). Ring chromosome 18 had the highest myelination lag (27, P = .005) and multifocal white matter changes (P = .001). Trisomy 18 had smaller pons and cerebellar dimensions (anteposterior diameter pons, P = .002; corpus callosum vermis, P < .001; and transverse cerebellar diameter, P = .04).

CONCLUSIONS

In this cohort of 18q chromosomal abnormalities, MR imaging revealed recognizable patterns correlating with improving brain myelination. Imaging findings appear to be on a continuum with more severe white matter abnormalities in ring chromosome 18 and greater prevalence of structural abnormalities of the pons and cerebellum in trisomy 18.

Mapping of pathological change in chronic fatigue syndrome using the ratio of T1- and T2-weighted MRI scans

Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (ME/CFS) subjects suffer from a variety of cognitive complaints indicating that the central nervous system plays a role in its pathophysiology. Recently, the ratio T1w/T2w has been used to study changes in tissue myelin and/or iron levels in neurodegenerative diseases such as multiple sclerosis and schizophrenia. In this study, we applied the T1w/T2w method to detect changes in tissue microstructure in ME/CFS patients relative to healthy controls. We mapped the T1w/T2w signal intensity values in the whole brain for forty-five ME/CFS patients who met Fukuda criteria and twenty-seven healthy controls and applied both region- and voxel-based quantification. We also performed interaction-with-group regressions with clinical measures to test for T1w/T2w relationships that are abnormal in ME/CFS at the population level. Region-based analysis showed significantly elevated T1w/T2w values (increased myelin and/or iron) in ME/CFS in both white matter (WM) and subcortical grey matter. The voxel-based group comparison with sub-millimetre resolution voxels detected very significant clusters with increased T1w/T2w in ME/CFS, mostly in subcortical grey matter, but also in brainstem and projection WM tracts. No areas with decreased T1w/T2w were found in either analysis. ME/CFS T1w/T2w regressions with heart-rate variability, cognitive performance, respiration rate and physical well-being were abnormal in both gray and white matter foci. Our study demonstrates that the T1w/T2w approach is very sensitive and shows increases in myelin and/or iron in WM and basal ganglia in ME/CFS.

Delineation of the nerve fiber bundles of the infant brain associated with aging using phase difference-enhanced imaging: a preliminary study

PURPOSE

The purpose of this study was to evaluate the delineation of nerve fiber bundles in the brainstem and optic radiation in infants associated with aging on T1WI, T2WI, and phase difference-enhanced (PADRE) images.

MATERIALS AND METHODS

We retrospectively reviewed 21 consecutive subjects < 2 years old who underwent brain MRI without abnormal imaging findings. Two neuroradiologists evaluated the eight nerve fiber bundles in the brainstem and optic radiation using a 3-point scale focused on the contrast to surrounding brain parenchyma. We also evaluated the signal ratio of the optic radiation to surrounding white matter on PADRE for each month age.

RESULTS

T2WI was able to delineate nerve fiber bundles better than T1WI at 1 month old, and the images gradually became unclear with aging. On PADRE, almost all nerve fiber bundles were unclear or invisible at 1 month old but gradually became clearer with aging. There was a significant negative correlation between age and the signal ratio of the optic radiation to surrounding white matter.

CONCLUSIONS

The PADRE imaging was able to delineate the nerve fiber bundles in infants, and the delineation gradually became clearer with aging. The combination of PADRE, T1WI, and T2WI would be useful for evaluation of nerve fiber bundles in infants.

Age related signal changes of the pituitary stalk on thin-slice magnetic resonance imaging in infants

PURPOSE

Signals of some brain regions change along with development in T1-weighted imaging (T1WI) in infants. This study aimed to assess the association of the signal intensity of the pituitary stalk on thin-slice T1WI with infant age.

METHODS

This retrospective study was performed in 89 infants (gestational age [GA], 25-41 weeks; postmenstrual age [PMA], 36-46 weeks; chronological age [CA], 4-141 days) without intracranial abnormalities. The signal ratio of the pituitary stalk/pons on thin-slice T1WI was calculated, and its correlations with GA, PMA, and CA were assessed. Additionally, the signal ratio of the anterior pituitary gland/pons was calculated, and its correlation with that of the pituitary stalk was assessed. The signal intensity and distribution of the pituitary stalk were visually rated, and their correlations with GA, PMA, and CA were assessed.

RESULTS

The signal ratio of the pituitary stalk was significantly positively correlated with GA (P < 0.001) and negatively correlated with CA (P < 0.001), but was not correlated with PMA. Stepwise multiple regression revealed that CA was independently associated with the signal ratio of the pituitary stalk (P < 0.001). GA was significantly higher (P < 0.05) and CA was significantly lower (P < 0.05) in infants with a high signal intensity and wide distribution of high signal intensity of the pituitary stalk.

CONCLUSIONS

The signal intensity of the pituitary stalk on T1WI was negatively correlated with CA in infants, which might be related to postnatal changes in the pars tuberalis of the pituitary stalk after birth in infants.

Age-related T2 relaxation times at 3 Tesla as a biomarker of infratentorial brain maturation

PURPOSE

The purpose of this study was to examine age-related, infratentorial changes in T₂ relaxation times during infancy and childhood using routine MRI data at 3 Tesla.

METHODS

One hundred patients (0-199 months) without signal abnormalities on conventional MRI were retrospectively selected from our pool of pediatric MRI examinations. T₂ maps based on our routinely acquired triple-echo turbo spin-echo (TSE) sequence were created. Based on their clinical symptoms, the children were divided into 43 controls and 57 diseased children with different clinical diseases. T₂ relaxation times were measured in 15 infratentorial brain regions (medullary pyramid, ventral and dorsal pons, middle cerebellar peduncle, dentate nucleus, medial and lateral cerebellar hemisphere each on both sides, and in the cerebellar vermis) investigating age-related changes. Secondly, this study examined whether those changes in T₂ values differed between healthy and diseased children.

RESULTS

Age significantly reduced T₂ relaxation time in all infratentorial brain regions (p < 0.05). With increasing age, the T₂ relaxation times decreased continuously, faster in the first 9 months and slower thereafter. Overall, controls did not differ significantly from diseased children (p > 0.05) apart from the dentate nucleus and cerebellar hemispheres in terms of rapid decline (larger in controls) and the right dorsal pons and left pyramid in terms of slow decline (larger in diseased children). In both groups, the later slow decline was almost negligible.

CONCLUSIONS

Using T₂ maps, it was possible to determine age-related T₂ relaxation times in the different infratentorial brain regions in this preliminary study. Between neurologically healthy controls and diseased children, no significant differences in T₂ relaxation times could be found overall in the studied regions.

Comparison of Silent and Conventional MR Imaging for the Evaluation of Myelination in Children

Purpose:

Silent magnetic resonance imaging (MRI) scans produce reduced acoustic noise and are considered more gentle for sedated children. The aim of this study was to compare the validity of T₁- (T₁W) and T₂-weighted (T₂W) silent sequences for myelination assessment in children with conventional spin-echo sequences.

Materials and Methods:

A total of 30 children (21 boys, 9 girls; age range: 1–83 months, mean age: 35.5 months, median age: 28.5 months) were examined using both silent and spin-echo sequences. Acoustic noise levels were analyzed and compared. The degree of myelination was qualitatively assessed via consensus, and T₁W and T₂W signal intensities were quantitatively measured by percent contrast.

Results:

Acoustic noise levels were significantly lower during silent sequences than during conventional sequences (P < 0.0001 for both T₁W and T₂W). Inter-method comparison indicated overall good to excellent agreement (T₁W and T₂W images, κ = 0.76 and 0.80, respectively); however, agreement was poor for cerebellar myelination on T₁W images (κ = 0.14). The percent contrast of silent and conventional MRI sequences had a strong correlation (T₁W, correlation coefficient [CC] = 0.76; T₁W excluding the middle cerebellar peduncle, CC = 0.82; T₂W, CC = 0.91).

Conclusions:

For brain MRI, silent sequences significantly reduced acoustic noise and provided diagnostic image quality for myelination evaluations; however, the two methods differed with respect to cerebellar delineation on T₁W sequences.