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Diffusion Tensor Magnetic Resonance Imaging in the Analysis of Neurodegenerative Diseases
Published on: July 28, 2013
Tensor-valued diffusion MRI differentiates cortex and white matter in malformations of cortical development
Björn Lampinen1, Ariadne Zampeli2, Isabella M Björkman-Burtscher3
1Clinical Sciences Lund, Medical Radiation Physics, Lund University, Lund, Sweden.
Objective:
Delineation of malformations of cortical development (MCD) is central in presurgical evaluation of drug-resistant epilepsy. Delineation using magnetic resonance imaging (MRI) can be ambiguous, however, because the conventional T1 - and T2 -weighted contrasts depend strongly on myelin for differentiation of cortical tissue and white matter. Variations in myelin content within both cortex and white matter may cause MCD findings on MRI to change size, become undetectable, or disagree with histopathology. The novel tensor-valued diffusion MRI (dMRI) technique maps microscopic diffusion anisotropy, which is sensitive to axons rather than myelin. This work investigated whether tensor-valued dMRI may improve differentiation of cortex and white matter in the delineation of MCD.
Methods:
Tensor-valued dMRI was performed on a 7 T MRI scanner in 13 MCD patients (age = 32 ± 13 years) featuring periventricular heterotopia, subcortical heterotopia, focal cortical dysplasia, and polymicrogyria. Data analysis yielded maps of microscopic anisotropy that were compared with T1 -weighted and T2 -fluid-attenuated inversion recovery images and with the fractional anisotropy from diffusion tensor imaging.
Results:
Maps of microscopic anisotropy revealed large white matter-like regions within MCD that were uniformly cortex-like in the conventional MRI contrasts. These regions were seen particularly in the deep white matter parts of subcortical heterotopias and near the gray-white boundaries of focal cortical dysplasias and polymicrogyrias.
Significance:
By being sensitive to axons rather than myelin, mapping of microscopic anisotropy may yield a more robust differentiation of cortex and white matter and improve MCD delineation in presurgical evaluation of epilepsy.
Insights
Tensor-valued diffusion MRI (dMRI) offers improved differentiation of cortical and white matter in malformations of cortical development (MCD). This technique, sensitive to axons, enhances MCD delineation for epilepsy presurgical evaluation.
Area of Science:
- Neuroimaging
- Medical Physics
- Neurology
Background:
- Accurate delineation of malformations of cortical development (MCD) is crucial for epilepsy presurgical evaluation.
- Conventional MRI contrasts (T1/T2-weighted) rely on myelin, leading to ambiguity in differentiating cortical and white matter in MCD.
- Myelin variations can alter MCD appearance on MRI, potentially causing discrepancies with histopathology.
Purpose of the Study:
- To investigate the utility of novel tensor-valued diffusion MRI (dMRI) for improved differentiation of cortex and white matter in MCD.
- To assess if tensor-valued dMRI can enhance the delineation of MCD in the context of epilepsy.
Main Methods:
- Tensor-valued dMRI was acquired using a 7 Tesla MRI scanner in 13 MCD patients.
- Patients presented with various MCD types including heterotopias, focal cortical dysplasia, and polymicrogyria.
- Microscopic anisotropy maps were generated and compared with conventional MRI (T1/T2) and diffusion tensor imaging (DTI).
Main Results:
- Microscopic anisotropy maps identified extensive white matter-like regions within MCD that appeared cortex-like on conventional MRI.
- These discrepancies were particularly noted in deep white matter of subcortical heterotopias and near gray-white matter boundaries in other MCD types.
- Tensor-valued dMRI revealed distinct patterns not apparent with standard MRI contrasts.
Conclusions:
- Tensor-valued dMRI, by mapping microscopic anisotropy sensitive to axons, provides more robust differentiation of cortex and white matter in MCD.
- This improved differentiation holds promise for enhancing MCD delineation in presurgical evaluations for drug-resistant epilepsy.
- The findings suggest tensor-valued dMRI as a valuable tool for complex neurodevelopmental disorder imaging.
