In vivo quantification of hippocampal subfields using 4.7 T fast spin echo imaging

Area of Science:

• Neuroimaging
• Neuroanatomy
• Neuroscience

Background:

• Neuropsychiatric disorders often involve hippocampal structural changes.
• Previous volumetric magnetic resonance imaging (MRI) studies primarily measured total hippocampal volume.
• A detailed understanding of hippocampal subfield distribution is lacking.

Purpose of the Study:

• To delineate and measure hippocampal subfields within the whole hippocampus.
• To analyze subfield volumes along the hippocampus's longitudinal axis.
• To establish normative data for subfield distribution in healthy subjects.

Main Methods:

• High-resolution MRI (4.7 T) was used in 11 healthy subjects.
• A fast spin echo (FSE) sequence provided native resolution of 0.52 x 0.68 x 1.0 mm³.
• Manual tracing of subiculum, cornu ammonis (CA1-3), and dentate gyrus was performed in hippocampal head, body, and tail.

Main Results:

• Significant differences in the distribution of subfields (dentate gyrus, CA1-3, subiculum) along the longitudinal axis were observed.
• The dentate gyrus was largest in the hippocampal body; CA1-3 was largest in the head; the subiculum was smallest in the tail.
• Subfield volumes were consistent between hemispheres and aligned with histological data.

Conclusions:

• Direct measurements of hippocampal subfield distribution are more sensitive for detecting disease effects than total volume.
• The differential distribution of subfield volumes aids in interpreting lower-resolution MRI data.
• This detailed subfield mapping provides a foundation for future clinical research in neuropsychiatric disorders.