Selection of voxel size and slice orientation for fMRI in the presence of susceptibility field gradients: application to imaging of the amygdala

The impact of voxel geometry on the blood oxygenation level-dependent (BOLD) signal detectability in the presence of field inhomogeneity is assessed and a quantitative approach to selecting appropriate voxel geometry is developed in this report. Application of the developed technique to BOLD sensiti...

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Vydané v:NeuroImage (Orlando, Fla.) Ročník 19; číslo 3; s. 817 - 825
Hlavní autori: Chen, Nan-Kuei, Dickey, Chandlee C, Yoo, Seung-Schik, Guttmann, Charles R.G, Panych, Lawrence P
Médium: Journal Article
Jazyk:English
Vydavateľské údaje: United States Elsevier Inc 01.07.2003
Elsevier Limited
Predmet:
Adult
Algorithms
Amygdala - anatomy & histology
Amygdala - metabolism
Fourier transforms
Geometry
Humans
Image Processing, Computer-Assisted
Magnetic Resonance Imaging - methods
Magnetic Resonance Imaging - statistics & numerical data
Male
NMR
Noise
Nuclear magnetic resonance
Oxygen - blood
Simulation
Studies
ISSN:1053-8119, 1095-9572
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Shrnutí:The impact of voxel geometry on the blood oxygenation level-dependent (BOLD) signal detectability in the presence of field inhomogeneity is assessed and a quantitative approach to selecting appropriate voxel geometry is developed in this report. Application of the developed technique to BOLD sensitivity improvement of the human amygdala is presented. Field inhomogeneity was measured experimentally at 1.5 T and 3 T and the dominant susceptibility field gradient in the human amygdala was observed approximately along the superior-inferior direction. Based on the field mapping studies, an optimal selection for the slice orientation would be an oblique pseudo-coronal plane with its frequency-encoding direction parallel to the field gradient measured from each subject. Experimentally this was confirmed by comparing the normalized standard deviation of time-series echo-planar imaging signals acquired with different slice orientations, in the absence of a functional stimulus. A further confirmation with a carefully designed functional magnetic resonance imaging study is needed. Although the BOLD sensitivity may generally be improved by a voxel size commensurable with the activation volume, our quantitative analysis shows that the optimal voxel size also depends on the susceptibility field gradient and is usually smaller than the activation volume. The predicted phenomenon is confirmed with a hybrid simulation, in which the functional activation was mathematically added to the experimentally acquired rest-period echo-planar imaging data.
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ISSN:1053-8119
1095-9572
DOI:10.1016/S1053-8119(03)00091-0