Spatial profiles provide sensitive MRI measures of the midbrain micro- and macrostructure.

Area of Science:

• Neuroscience
• Neuroimaging
• Anatomy

Background:

• The midbrain, a key brainstem region, is crucial for motor, auditory, and visual functions.
• Structural and functional changes in the midbrain are linked to aging and neurodegenerative diseases.
• Current MRI techniques for midbrain analysis require high resolution and complex quantitative measures.

Purpose of the Study:

• To develop and validate a novel, morphology-based approach for analyzing midbrain structure using simple measurements.
• To demonstrate the sensitivity of midbrain profiles to underlying macrostructure and specific subregions.
• To establish the robustness and generalizability of this method across different datasets and MRI metrics.

Main Methods:

• Calculating morphological profiles along three axes within the midbrain in subject-specific space.
• Utilizing R1, R2*, and Quantitative Susceptibility Mapping (QSM) data from two MRI datasets with varying field strengths.
• Validating profile accuracy by comparing with Region of Interest (ROI) sampling and analyzing age-related differences.

Main Results:

• Midbrain profiles demonstrated high cross-subject and cross-dataset correlation, indicating reliability.
• Profiles effectively differentiated key midbrain structures, including the substantia nigra, red nucleus, and periaqueductal gray.
• Age-related structural changes localized to specific nuclei were successfully reflected in the midbrain profiles.

Conclusions:

• Midbrain morphology profiles, derived from both quantitative and semi-quantitative MRI data, are sensitive to the brainstem's macrostructure.
• This robust, easily applicable method, calculated in native space, can be expanded to diverse datasets, aiding midbrain research.
• The proposed approach offers a valuable, accessible tool for studying the midbrain in aging and disease contexts.