Journal
MAGNETIC RESONANCE IN MEDICINE
Volume 79, Issue 3, Pages 1616-1627Publisher
WILEY
DOI: 10.1002/mrm.26781
Keywords
magnetic resonance; relaxation; rat; cerebral cortex; cultured cells
Funding
- NIH/NINDS [R01-NS030888]
- NIH/NIBIB [R01-EB002083]
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PurposeTo determine the intracellular water preexchange lifetime, (i), the average residence time of water, in the intracellular milieu of neurons and astrocytes. The preexchange lifetime is important for modeling a variety of MR data sets, including relaxation, diffusion-sensitive, and dynamic contrast-enhanced data sets. MethodsHerein, (i) in neurons and astrocytes is determined in a microbead-adherent, cultured cell system. In concert with thin-slice selection, rapid flow of extracellular media suppresses extracellular signal, allowing determination of the transcytolemmal-exchange-dominated, intracellular T-1. With this knowledge, and that of the intracellular T-1 in the absence of exchange, (i) can be derived. ResultsUnder normal culture conditions, (i) for neurons is 0.750.05 s versus 0.57 +/- 0.03 s for astrocytes. Both neuronal and astrocytic (i)s decrease within 30min after the onset of oxygen-glucose deprivation, with the astrocytic (i) showing a substantially greater decrease than the neuronal (i). ConclusionsGiven an approximate intra- to extracellular volume ratio of 4:1 in the brain, these data imply that, under normal physiological conditions, an MR experimental characteristic time of less than 0.012 s is required for a nonexchanging, two-compartment (intra- and extracellular) model to be valid for MR studies. This characteristic time shortens significantly (i.e., 0.004 s) under injury conditions. Magn Reson Med 79:1616-1627, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.
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