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A Comprehensive Protocol for Manual Segmentation of the Medial Temporal Lobe Structures
Published on: July 2, 2014
A protocol for manual segmentation of medial temporal lobe subregions in 7 Tesla MRI
D Berron1, P Vieweg2, A Hochkeppler3
1Institute of Cognitive Neurology and Dementia Research, Otto-von-Guericke-University Magdeburg, 39120 Magdeburg, Germany; German Center for Neurodegenerative Diseases (DZNE), Site Magdeburg, 39120 Magdeburg, Germany.
Abstract:
Recent advances in MRI and increasing knowledge on the characterization and anatomical variability of medial temporal lobe (MTL) anatomy have paved the way for more specific subdivisions of the MTL in humans. In addition, recent studies suggest that early changes in many neurodegenerative and neuropsychiatric diseases are better detected in smaller subregions of the MTL rather than with whole structure analyses. Here, we developed a new protocol using 7 Tesla (T) MRI incorporating novel anatomical findings for the manual segmentation of entorhinal cortex (ErC), perirhinal cortex (PrC; divided into area 35 and 36), parahippocampal cortex (PhC), and hippocampus; which includes the subfields subiculum (Sub), CA1, CA2, as well as CA3 and dentate gyrus (DG) which are separated by the endfolial pathway covering most of the long axis of the hippocampus. We provide detailed instructions alongside slice-by-slice segmentations to ease learning for the untrained but also more experienced raters. Twenty-two subjects were scanned (19-32 yrs, mean age = 26 years, 12 females) with a turbo spin echo (TSE) T2-weighted MRI sequence with high-resolution oblique coronal slices oriented orthogonal to the long axis of the hippocampus (in-plane resolution 0.44 × 0.44 mm2) and 1.0 mm slice thickness. The scans were manually delineated by two experienced raters, to assess intra- and inter-rater reliability. The Dice Similarity Index (DSI) was above 0.78 for all regions and the Intraclass Correlation Coefficients (ICC) were between 0.76 to 0.99 both for intra- and inter-rater reliability. In conclusion, this study presents a fine-grained and comprehensive segmentation protocol for MTL structures at 7 T MRI that closely follows recent knowledge from anatomical studies. More specific subdivisions (e.g. area 35 and 36 in PrC, and the separation of DG and CA3) may pave the way for more precise delineations thereby enabling the detection of early volumetric changes in dementia and neuropsychiatric diseases.
Insights
This study introduces a detailed 7 Tesla MRI protocol for segmenting medial temporal lobe (MTL) subregions, crucial for detecting early disease changes. The protocol demonstrates high reliability for precise anatomical delineation in neuroimaging research.
Area of Science:
- Neuroimaging
- Neuroanatomy
- Radiology
Background:
- Advances in 7 Tesla MRI and anatomical knowledge enable finer subdivisions of the medial temporal lobe (MTL).
- Early detection of neurodegenerative and neuropsychiatric diseases may benefit from analyzing smaller MTL subregions.
Purpose of the Study:
- To develop and validate a high-resolution manual segmentation protocol for detailed MTL structures using 7 Tesla MRI.
- To provide a standardized method for segmenting entorhinal cortex, perirhinal cortex (areas 35 and 36), parahippocampal cortex, and hippocampal subfields.
Main Methods:
- Utilized 7 Tesla MRI with high-resolution oblique coronal slices (0.44x0.44 mm in-plane, 1.0 mm slice thickness).
- Developed a manual segmentation protocol for specific MTL regions including entorhinal cortex, perirhinal cortex (areas 35, 36), parahippocampal cortex, and hippocampal subfields (Sub, CA1-3, DG).
- Assessed intra- and inter-rater reliability using Dice Similarity Index (DSI) and Intraclass Correlation Coefficients (ICC) in 22 subjects.
Main Results:
- Achieved DSI > 0.78 for all segmented regions, indicating high overlap.
- Reported ICC values between 0.76 and 0.99 for both intra- and inter-rater reliability, demonstrating excellent consistency.
- The protocol successfully delineated fine-grained MTL subregions, including area 35/36 and separation of DG/CA3.
Conclusions:
- Presents a reliable and comprehensive 7 Tesla MRI segmentation protocol for detailed MTL anatomy.
- This fine-grained approach supports precise volumetric analysis for early detection of changes in neurological and psychiatric diseases.
- The protocol's detailed instructions facilitate its adoption by researchers for enhanced neuroimaging studies.
