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Effects of biophysical and physiologic parameters on brain activation‐induced R 2 * and R 2 changes: Simulations using a deterministic diffusion model
Author(s) -
Bandettini Peter A.,
Wong Eric C.
Publication year - 1995
Publication title -
international journal of imaging systems and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.359
H-Index - 47
eISSN - 1098-1098
pISSN - 0899-9457
DOI - 10.1002/ima.1850060203
Subject(s) - nuclear magnetic resonance , diffusion , physics , intravoxel incoherent motion , relaxation (psychology) , voxel , cerebral blood flow , radius , chemistry , magnetic resonance imaging , effective diffusion coefficient , thermodynamics , neuroscience , computer science , medicine , computer security , artificial intelligence , biology , cardiology , radiology
A central issue in magnetic resonance imaging of human brain function using blood oxygenation level‐dependent (BOLD) contrast is the accurate interpretation of the signal changes that are observed. Using a method that incorporates repeated phase rotation and convolution with a smoothing function to simulate spin diffusion in the presence of magnetic field perturbers, the dependencies of the absolute and relative changes in transverse relaxation rates (δ R 2 * and δ R 2 ) on biophysical and physiologic parameters were explored. First we introduce the modeling methodology. Then we simulate δ R 2 * and δ R 2 as physiologic and biophysical parameters are modulated within the ranges that they vary across subjects and voxels in the brain. The simulations demonstrate that the δ R 2 * and δ R 2 values that occur with activation‐induced changes in blood oxygenation depend most strongly on the resting state blood volume and field strength. The δ R 2 */δ R 2 ratios depend most strongly on the vessel radius and spin diffusion coefficient.