Quantitative sodium MRI of the human brain at 9.4 T provides assessment of tissue sodium concentration and cell volume fraction during normal aging

Sodium ion homeostasis is a fundamental property of viable tissue, allowing the tissue sodium concentration to be modeled as the tissue cell volume fraction. The modern neuropathology literature using ex vivo tissue from selected brain regions indicates that human brain cell density remains constant...

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Bibliographic Details
Published in:NMR in biomedicine 2016-02, Vol.29 (2), p.137-143
Main Authors: Thulborn, Keith, Lui, Elaine, Guntin, Jonathan, Jamil, Saad, Sun, Ziqi, Claiborne, Theodore C., Atkinson, Ian C.
Format: Article
Language:English
Subjects:
ageing
Aging - metabolism
Algorithms
brain
Brain - cytology
Brain - metabolism
Cell Size
cognition
Female
human
Humans
Magnetic Resonance Imaging - methods
Male
Middle Aged
MRI
normal
quantitative
sodium
Sodium - metabolism
Young Adult
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Summary:Sodium ion homeostasis is a fundamental property of viable tissue, allowing the tissue sodium concentration to be modeled as the tissue cell volume fraction. The modern neuropathology literature using ex vivo tissue from selected brain regions indicates that human brain cell density remains constant during normal aging and attributes the volume loss that occurs with advancing age to changes in neuronal size and dendritic arborization. Quantitative sodium MRI performed with the enhanced sensitivity of ultrahigh‐field 9.4 T has been used to investigate tissue cell volume fraction during normal aging. This cross‐sectional study (n = 49; 21–80 years) finds that the in vivo tissue cell volume fraction remains constant in all regions of the brain with advancing age in individuals who remain cognitively normal, extending the ex vivo literature reporting constant neuronal cell density across the normal adult age range. Cell volume fraction, as measured by quantitative sodium MRI, is decreased in diseases of cell loss, such as stroke, on a time scale of minutes to hours, and in response to treatment of brain tumors on a time scale of days to weeks. Neurodegenerative diseases often have prodromal periods of decades in which regional neuronal cell loss occurs prior to clinical presentation. If tissue cell volume fraction can detect such early pathology, this quantitative parameter may permit the objective measurement of preclinical disease progression. This current study in cognitively normal aging individuals provides the basis for the pursuance of investigations directed towards such neurodegenerative diseases. Copyright © 2015 John Wiley & Sons, Ltd. Quantitative sodium MRI at 9.4 T performed on human brains shows that the tissue sodium concentration (TSC) and cell volume fraction remain constant during cognitively normal ageing, confirming a result previously available only from neuropathology. The figure shows TSC of the brain as a function of adult age. Representative images of TSC (top) and tissue cell volume fraction (bottom) are shown across the age scale for representative young and old individuals. Images were acquired at 9.4 T.
ISSN:0952-3480
1099-1492
DOI:10.1002/nbm.3312