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Age-dependent changes in magnetization transfer contrast of white matter in the pediatric brain
V Engelbrecht1, M Rassek, S Preiss
1Institute of Diagnostic Radiology, Heinrich-Heine-University, Düsseldorf, Germany.
Insights
Magnetization transfer contrast (MTC) in the pediatric brain significantly increases with myelination, correlating inversely with T2 relaxation times. This study quantifies these age-dependent changes in white matter development.
Area of Science:
- Neuroimaging
- Biophysics
- Pediatric Radiology
Background:
- Myelination is a critical process in pediatric brain development.
- Magnetization transfer contrast (MTC) is a sensitive MRI technique.
- The relationship between MTC and myelination in the pediatric brain is not well understood.
Purpose of the Study:
- To measure age-dependent changes in white matter MTC in children.
- To evaluate the correlation between MTC and T2 relaxation times during brain development.
- To understand the impact of myelination on MTC in the pediatric brain.
Main Methods:
- MRI scans were acquired from 70 children (1 week to 80 months).
- Magnetization transfer contrast (MTC) ratios and T2 relaxation times were calculated in 13 brain regions.
- Regression analysis assessed age dependency of MTC and T2 relaxation times.
Main Results:
- White matter MTC increased from 13-19% to 34-37% with myelination.
- T2 relaxation times decreased from 115-160 ms to 60-70 ms post-myelination.
- Both MTC and T2 relaxation times showed age dependency described by a monoexponential function.
Conclusions:
- A strong positive correlation exists between MTC and myelination in the pediatric brain.
- An inverse correlation was observed between MTC and T2 relaxation times.
- Proton relaxation in macromolecules likely explains decreasing T2 times during myelination.
Background And Purpose:
It is unknown to what extent magnetization transfer contrast (MTC) in white matter of the brain changes during myelination. The goal of this study was to measure the age-dependent changes of MTC in different regions of the pediatric brain and to evaluate their relation to T2 relaxation times.
Methods:
Seventy children aged 1 week to 80 months without evidence of organic brain disease underwent MR imaging of the brain. A double-echo spin-echo (SE) sequence and an SE sequence with and without an off-resonance pulse were performed in the axial orientation. Using paired images, we calculated MTC ratios in 13 predefined regions of the brain and compared them with the T2 relaxation times measured in the same areas. Regression analysis was performed for both parameters to evaluate age dependency.
Results:
MTC in white matter increased during myelination from a range of 13% to 19% to a range of 34% to 37%. At the same time, T2 relaxation times decreased from a range of 115 to 160 milliseconds to a range of 60 to 70 milliseconds after myelination. For both MTC and T2 relaxation times, age dependency could be expressed by a monoexponential function.
Conclusion:
A strong positive correlation exists between MTC ratios and the degree of myelination in the pediatric brain, and an inverse correlation exists between MTC and T2 relaxation times. Fast proton relaxation within macromolecules in the myelinated white matter and subsequent MT may be the most important reason for the decreasing T2 relaxation time of white matter during brain myelination.