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In vivo quantification of the limbic system using MRI: effects of normal aging
K O Lim1, R B Zipursky, G M Murphy
1Psychiatry Service, VA Medical Center, Palo Alto, CA 94304.
Abstract:
Limbic system structures are of central interest in many neuropsychiatric disorders. Magnetic resonance imaging (MRI) has a unique potential for imaging limbic system structures in vivo, but methodological constraints can limit the usefulness and interpretation of the collected image data. In this article, we present approaches for the acquisition and quantification of high resolution MR images of the limbic system. We used a long TR, cardiac gated, flow compensated, spin echo sequence to collect 22, 3-mm thick contiguous sections encompassing the limbic system. The sections were oriented relative to standard internal neuroanatomical landmarks. The sequence provided good gray matter/white matter/cerebrospinal fluid (CSF) and CSF/bone contrast; the latter is necessary for quantifying intracranial size and total CSF volume. Using operationalized criteria, we achieved high interrater reliability in volumetric measurement of temporal horn and hippocampus. This technique was then used to examine the effect of normal aging by comparing eight young (mean = 24 years) and seven old (mean = 73 years) healthy community members. We were able to demonstrate a significant age-related increase in temporal horn volume and a trend toward an age-related decrease in hippocampal volume.
Insights
High-resolution magnetic resonance imaging (MRI) reveals age-related changes in the limbic system. This study found increased temporal horn volume and a trend for decreased hippocampal volume in older adults.
Area of Science:
- Neuroimaging
- Neuroanatomy
- Gerontology
Background:
- Limbic system structures are crucial in neuropsychiatric disorders.
- Magnetic resonance imaging (MRI) offers in vivo imaging potential but faces methodological constraints.
- Accurate imaging and quantification of the limbic system are vital for research and clinical applications.
Purpose of the Study:
- To present optimized methods for acquiring and quantifying high-resolution MRI data of the limbic system.
- To assess the reliability of volumetric measurements for key limbic structures.
- To investigate the effects of normal aging on limbic system volumes.
Main Methods:
- Utilized a cardiac-gated, flow-compensated, spin echo MRI sequence with a long TR.
- Acquired 3-mm thick contiguous sections covering the limbic system, oriented to neuroanatomical landmarks.
- Employed operationalized criteria for reliable volumetric quantification of the temporal horn and hippocampus.
Main Results:
- Achieved good contrast for gray matter, white matter, cerebrospinal fluid (CSF), and CSF/bone interfaces.
- Demonstrated high interrater reliability in volumetric measurements of the temporal horn and hippocampus.
- Observed a significant age-related increase in temporal horn volume and a trend toward decreased hippocampal volume in older adults.
Conclusions:
- Developed and validated a robust MRI methodology for high-resolution limbic system imaging.
- The findings suggest specific volumetric alterations in the limbic system associated with normal aging.
- This technique provides a valuable tool for studying limbic system morphology in aging and neuropsychiatric conditions.