Spatial and temporal characteristics of physiological noise in fMRI at 3T.

Rationale And Objectives: Physiological noise in blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) has been shown to have characteristics similar to the BOLD signal itself, suggesting that it may have a vascular dependence. In this study, we evaluated the influence of physiological noise in fMRI as revealed by the differences in vasculature sensitivity of gradient-echo echo-planar imaging (GE-EPI) and spin-echo EPI (SE-EPI).

Materials And Methods: The contribution of physiological noise to the fMRI signal during activation of the visual cortex was assessed by comparing its temporal characteristics with respect to echo time (TE), using both GE-EPI and SE-EPI.

T1rho contrast in functional magnetic resonance imaging.

The application of T1 in the rotating frame (T1rho) to functional MRI in humans was studied at 3 T. Increases in neural activity increased parenchymal T1rho. Modeling suggested that cerebral blood volume mediated this increase.

Temporal resolving power of spin echo and gradient echo fMRI at 3T with apparent diffusion coefficient compartmentalization.

The temporal resolving power of blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T was investigated in the visual and auditory cortices of the human brain. By using controlled temporal delays and selective visual hemifield stimulation, regions with similar (left vs. right occipital cortex) and different (occipital cortex vs.

Spatial sensitivity and temporal response of spin echo and gradient echo bold contrast at 3 T using peak hemodynamic activation time.

Recent theoretical and experimental work has suggested that spin echo (SE) functional MRI (fMRI) has improved localization of neural activity compared to gradient echo (GE) fMRI at high field strengths, albeit with a decrease in blood oxygenation level-dependent (BOLD) contrast. The present study investigated spatial and temporal variations in GE and SE fMRI at 3 T in response to a brief visual stimulus. The results demonstrate that SE BOLD contrast reaches its maximum amplitude more quickly than does GE contrast at long echo times.

The effects of geometric distortion correction on motion realignment in fMRI.

Rationale And Objectives: Subject motion is well recognized as a significant impediment to resolution and sensitivity in functional magnetic resonance imaging (fMRI). A parallel confounder to fMRI data quality is geometric image distortion, particularly at high field strengths, due to susceptibility-induced magnetic field inhomogeneity. Consequently, many high-field echo-planar imaging methods incorporate a post-processing distortion correction by acquiring a field map of the sample prior to the fMRI measurement.

Balance of mass, momentum, and energy in splintering central collisions for 40Ar up to 115 MeV /Nucleon.

For central collisions of (17-115)A MeV 40Ar+Cu, Ag, Au, an overall balance is determined for the average mass, energy, and longitudinal momentum. Light charged particles and fragments are separated into forward-focused and isotropic components in the frame of the heaviest fragment. Energy removal by the isotropic component reaches 1-2 GeV.