The lag of cerebral hemodynamics with rapidly alternating periodic stimulation: modeling for functional MRI

A mathematical model that characterizes the response of venous oxygenation to changes in cerebral blood flow (rCBF) and oxygen consumption has been previously presented. We use this model to examine the dampening phenomenon in functional MRI (fMRI) signals with rapidly alternating periodic stimulati...

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Bibliographic Details
Published in:Magnetic resonance imaging 1999-01, Vol.17 (1), p.9-20
Main Authors: Hathout, Gasser M, Gopi, Ramesh K, Bandettini, Peter, Gambhir, Sanjiv S
Format: Article
Language:English
Subjects:
Biological and medical sciences
Blood Flow Velocity
Blood oxygenation
Cerebral blood flow
Cerebral hemodynamics
Cerebrovascular Circulation
Functional MRI
Humans
Impulse–Response
Investigative techniques, diagnostic techniques (general aspects)
Magnetic Resonance Imaging
Medical sciences
Models, Theoretical
MR activation
Nervous system
Oxygen - blood
Photic Stimulation
Radiodiagnosis. Nmr imagery. Nmr spectrometry
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Summary:A mathematical model that characterizes the response of venous oxygenation to changes in cerebral blood flow (rCBF) and oxygen consumption has been previously presented. We use this model to examine the dampening phenomenon in functional MRI (fMRI) signals with rapidly alternating periodic stimulation bursts. Using a mass balance approach, the equations for an input-output model are derived and solved using Matlab (the Math Works Inc.). Changes in venous oxygenation are related to the results of fMRI experiments using progressively shorter periods of stimulation. An impulse-response function for the model is derived in an attempt to explore the source of the lag in cerebral hemodynamics. Increasing the frequency of stimulation bursts eventually produces a dampening in the fMRI signal. The dampening phenomenon in fMRI signals occurs with stimulation of high frequency on-off alternation. The dynamics of signal dampening, as well as the impulse-response function of a blood oxygen level-dependent model, lend strong indirect support to the hypothesis that blood oxygen level-dependent contrast at the level of the venous blood pool, rather than R1 inflow effects or changes in oxygenation at the level of the capillary bed, underlies the observed signal changes in fMRI.
ISSN:0730-725X
1873-5894
DOI:10.1016/S0730-725X(98)00150-7