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Identification of "premyelination" by diffusion-weighted MRI
D M Wimberger1, T P Roberts, A J Barkovich
1Department of Radiology, University of Vienna, Wien, Austria.
Objective:
The purpose of this study was to compare white matter maturation as demonstrated with diffusion-weighted MRI and with myelin-sensitive histological staining.
Materials And Methods:
The diffusion-, T1-, and T2-weighted SE MRI at 4.7 T was performed weekly in a total of 16 rat pups, aged from 5 days to 8 weeks, 2 animals evaluated per week. Heavily diffusion-weighted sequences were obtained with the diffusion-sensitizing gradient switched alternately in two orthogonal directions. To enhance signal intensity of anisotropic structures, a synthesized image (referred to as the "anisotropy index map") was constructed from the ratio of pairs of images acquired with diffusion sensitization of identical magnitude but orthogonal direction sensitivity. The anisotropy index maps were used for comparison with T1-weighted and heavily T2-weighted SE sequences and histological sections, respectively.
Results:
The first evidence of diffusion anisotropy on anisotropy index maps preceded initial myelin as well as neurofibril staining by 5-12 days and T2 shortening by 2 weeks. The T1-weighted sequences did not yield visible changes and were not helpful for the assessment of ongoing white matter maturation in this model.
Conclusion:
Magnetic resonance imaging signal intensity changes based on anisotropic water diffusion were demonstrated in regions of unmyelinated cerebral white matter tracts of albino rat pups before the onset of histologically detectable myelin. The ability of in vivo mapping of premyelinating white matter maturation indicates a new diagnostic use of MRI in evaluating cerebral white matter maturation.
Insights
Diffusion-weighted MRI detected white matter maturation in rat pups before myelin staining. This magnetic resonance imaging technique allows for in vivo mapping of premyelinating white matter development.
Area of Science:
- Neuroimaging
- Developmental Neuroscience
- Biomedical Engineering
Background:
- White matter maturation is crucial for brain development.
- Assessing white matter maturation typically involves histological staining, which is invasive.
- Diffusion-weighted MRI offers a non-invasive method to study tissue microstructure.
Purpose of the Study:
- To compare white matter maturation using diffusion-weighted MRI and myelin-sensitive histological staining.
- To evaluate the efficacy of MRI in detecting early stages of white matter development.
Main Methods:
- Weekly diffusion-, T1-, and T2-weighted MRI scans were performed on rat pups (5 days to 8 weeks old).
- Anisotropy index maps were synthesized from diffusion-weighted images to highlight anisotropic structures.
- Anisotropy index maps were compared with T1-weighted, T2-weighted MRI, and histological sections.
Main Results:
- Diffusion anisotropy was observed on anisotropy index maps 5-12 days before myelin staining.
- Diffusion anisotropy preceded T2 shortening by 2 weeks.
- T1-weighted sequences were not effective for assessing white matter maturation in this model.
Conclusions:
- Magnetic resonance imaging signal changes reflecting anisotropic water diffusion were detected in unmyelinated white matter tracts before myelin was histologically visible.
- In vivo mapping of premyelinating white matter maturation using MRI is feasible.
- This study suggests a new diagnostic application for MRI in evaluating cerebral white matter maturation.