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High-resolution In Vivo Manual Segmentation Protocol for Human Hippocampal Subfields Using 3T Magnetic Resonance Imaging
Published on: November 10, 2015
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High-resolution microscopic diffusion anisotropy imaging in the human hippocampus at 3T
Jiyoon Yoo1, Leevi Kerkelä1, Patrick W Hales1
1Developmental Imaging and Biophysics Section, UCL Great Ormond Street Institute of Child Health, London, United Kingdom.
Magnetic Resonance in Medicine
|November 29, 2021
Summary
This study introduces a novel high-resolution diffusion imaging method for the hippocampus, offering better insights into brain microstructure. The technique provides reliable measurements of microscopic anisotropy and diffusion size variance in healthy individuals.
Area of Science:
- Neuroimaging
- Diffusion MRI
- Microstructural analysis
Background:
- Neurological conditions often manifest as hippocampal microstructural changes detectable by diffusion-weighted imaging (DWI).
- Current whole-brain DWI protocols limit resolution and exacerbate partial-volume effects.
- Conventional methods struggle to differentiate microscopic diffusion anisotropy from variations in diffusion environment size.
Purpose of the Study:
- To implement a multidimensional diffusion-encoding protocol for high-resolution hippocampal microstructural imaging.
- To overcome limitations of conventional DWI in assessing hippocampal microstructure.
- To investigate microscopic diffusion anisotropy and size variance in the human hippocampus.
Main Methods:
- Acquisition of high-resolution (1.5-mm isotropic) DWI data from 8 healthy volunteers using a custom multidimensional diffusion-encoding sequence.
- Estimation of microscopic fractional anisotropy (µFA) and normalized size variance (CMD) via q-space trajectory imaging.
- Comparison of µFA and CMD with conventional diffusion tensor imaging (DTI) metrics; assessment of protocol reproducibility and optimization for shorter scan times (14 minutes).
Main Results:
- Mean µFA (0.47) was significantly higher than mean FA (0.20), indicating substantial orientation dispersion in hippocampal microstructure.
- Mean CMD was determined to be 0.17.
- Q-space trajectory imaging metrics demonstrated reproducibility comparable to DTI, with reference values for healthy hippocampal microstructure established.
Conclusions:
- Demonstrated the feasibility of high-resolution microscopic anisotropy imaging in the human hippocampus at 3 Tesla.
- Provided essential reference values for microstructural metrics in a healthy hippocampus.
- Highlighted the potential of advanced diffusion encoding techniques for detailed neuroanatomical studies.
