Development of a histologically validated segmentation protocol for the hippocampal body

Area of Science:

• Neuroimaging
• Neuroanatomy
• Histology

Background:

• Hippocampal subfield segmentation is crucial for understanding disease-related changes.
• Current in vivo MRI segmentation lacks histological validation.
• MRI-visible landmarks are essential for accurate segmentation.

Purpose of the Study:

• Develop and validate a novel hippocampal body segmentation method using MRI landmarks.
• Compare the novel method's accuracy against existing techniques and histological gold standards.
• Assess the feasibility of applying the novel method to in vivo MRI studies.

Main Methods:

• Developed a novel segmentation protocol for the hippocampal body using stratum lacunosum moleculare (SLM) and dentate gyrus (DG) landmarks.
• Performed ultra-high resolution ex vivo MRI on cadaveric hippocampi, followed by histological processing.
• Compared segmentation accuracy of the novel method and two published strategies against direct histological measurements.

Main Results:

• The novel method accurately measured CA1/CA2 (ICC=0.93) and CA2/CA3 (ICC=0.97) boundaries on histology.
• Published methods showed lower accuracy, particularly for the Subiculum/CA1 boundary.
• Ex vivo MRI measurements using the novel method correlated with histological findings for SLM length and CA1/CA2, CA2/CA3 boundaries.

Conclusions:

• A novel segmentation method utilizing SLM and DG landmarks provides accurate hippocampal subfield measurements.
• The developed method demonstrates high accuracy compared to existing techniques and histological data.
• Findings support the potential application of this method for in vivo MRI studies of hippocampal anatomy.