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This study has investigated the effects of the selection of the diffusion-weighted (DW) gradient directions on the precision of a diffusion tensor imaging (DTI) experiment. The theoretical analysis provided a quantitative framework in which the noise performance of DTI schemes could be assessed objectively and for the development of novel DTI schemes, which(More)
This work studies the effect of diffusion-weighting on the precision of measurements of the apparent diffusion coefficient (ADC, or D) by diffusion-weighted magnetic resonance imaging. The precision in the value of the ADC was described in terms of a diffusion-to-noise ratio (DNR) which was calculated as the signal-to-noise ratio in the resultant ADC. A(More)
Cortical spreading depression (CSD) in the gyrencephalic cat brain was detected with diffusion-weighted echoplanar (DWEP) magnetic resonance imaging (4-8/min for 1-2 hours) using a horizontal imaging plane through the suprasylvian (SG) and marginal gyri. A t-statistic mapping technique allowed a quantitative characterization of the passage of events through(More)
The dependence of BOLD signal change (BSC) on baseline hematocrit is in the process of being characterized, primarily using conventional Gradient Echo (GE) echo planar imaging (EPI). We describe the first empiric exploration of this relationship using, in addition to GE, Spin Echo (SE) and two Asymmetric Spin Echo EPI sequences (ASE10 and ASE20), which are(More)
This study investigated the properties of a class of rotationally invariant and symmetric (relative to the principal diffusivities) indices of the anisotropy of water self-diffusion, namely fractional anisotropy (FA), relative anisotropy (RA), and volume ratio (VR), with particular emphasis to their measurement in brain tissues. A simplified theoretical(More)
This study has investigated the relationship between the noise sensitivity of measurement by magnetic resonance imaging (MRI) of the diffusion tensor (D) of water and the number N of diffusion-weighting (DW) gradient directions, using computer simulations of strongly anisotropic fibers with variable orientation. The DW directions uniformly sampled the(More)
1.Time-lapse diffusion-weighted magnetic resonance imaging (DWI) was used to detect and characterize complex waves of cortical spreading depression (CSD) evoked with KCL placed upon the suprasylvian gyrus of anaesthetized cats. 2. The time-lapse representations successfully demonstrated primary CSD waves that propagated with elliptical wavefronts(More)
Functional MRI (fMRI) was used to investigate the effects of psychotropic compound activity in the rat brain in vivo. The effects of dizocilpine (MK-801) an N-methyl-D-aspartate receptor antagonist and m-chlorophenylpiperazine (mCPP), a 5-HT(2b/2c)-receptor agonist on rat brain activity were investigated over a time interval of about 1 h and the results(More)
This article describes a method which enables fast and objective pulse-sequence-specific preemphasis calibration, using standard pulse sequences and system hardware. The method is based on a k-space measurement technique, and has been applied to single-shot, diffusion-weighted, spin-echo, echo-planar imaging (DW-SE-EPI), which is particularly sensitive to(More)
Autoradiographic studies have shown that low dose ketamine produces increases in regional glucose utilisation and blood flow in the hippocampus, cerebral cortex, and olfactory lobe in the rat brain, probably due to antagonism at the NMDA receptor. Functional MRI using deoxyhaemoglobin contrast can be used to study changes in regional cerebral blood flow(More)