|
| ||
|
|
||
BOLD Imaging (bold + imaging)
Selected AbstractsCorticothalamic Modulation during Absence Seizures in Rats: A Functional MRI AssessmentEPILEPSIA, Issue 9 2003Jeffrey R. Tenney Summary:,Purpose: Functional magnetic resonance imaging (fMRI) was used to identify areas of brain activation during absence seizures in an awake animal model. Methods: Blood-oxygenation-level,dependent (BOLD) fMRI in the brain was measured by using T2*-weighted echo planar imaging at 4.7 Tesla. BOLD imaging was performed before, during, and after absence seizure induction by using ,-butyrolactone (GBL; 200 mg/kg, intraperitoneal). Results: The corticothalamic circuitry, critical for spike,wave discharge (SWD) formation in absence seizure, showed robust BOLD signal changes after GBL administration, consistent with EEG recordings in the same animals. Predominantly positive BOLD changes occurred in the thalamus. Sensory and parietal cortices showed mixed positive and negative BOLD changes, whereas temporal and motor cortices showed only negative BOLD changes. Conclusions: With the BOLD fMRI technique, we demonstrated signal changes in brain areas that have been shown, with electrophysiology experiments, to be important for generating and maintaining the SWDs that characterize absence seizures. These results corroborate previous findings from lesion and electrophysiological experiments and show the technical feasibility of noninvasively imaging absence seizures in fully conscious rodents. [source] Assessment of regional myocardial oxygenation changes in the presence of coronary artery stenosis with balanced SSFP imaging at 3.0T: Theory and experimental evaluation in caninesJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 5 2008Rohan Dharmakumar PhD Abstract Purpose To examine the dependence of steady-state free-precession (SSFP) -based myocardial blood-oxygen-level-dependent (BOLD) contrast on field strength using theoretical and experimental models. Materials and Methods Numerical simulations using a two-pool exchange model and a surgically prepared dog model were used to assess the SSFP-based myocardial BOLD signal changes at 1.5T and 3.0T. Experimental studies were performed in eight canines with pharmacological vasodilation under various levels of left circumflex coronary artery stenosis. Experimentally obtained BOLD signal changes were correlated against microsphere-based true flow changes. Results Theoretical results showed that, at 3.0T, relative to 1.5T, a threefold increase in oxygen sensitivity can be expected. Experimental studies in canines showed near similar results,a 2.5 ± 0.2-fold increase in BOLD sensitivity at 3.0T relative to 1.5T (P < 0.05). Based on the scatter gram of BOLD data and microsphere data, it was found that the minimum regional flow difference that can be detected with SSFP-based myocardial BOLD imaging at 1.5T and 3.0T were 2.9 and 1.6, respectively (P < 0.05). Conclusion This study demonstrated that SSFP-based myocardial BOLD sensitivity is substantially greater at 3.0T compared with 1.5T. The findings here suggest that SSFP-based myocardial BOLD imaging at 3.0T may have the necessary sensitivity to detect the clinically required minimum flow difference of 2.0. J. Magn. Reson. Imaging 2008;27:1037,1045. © 2008 Wiley-Liss, Inc. [source] Assessment of regional differences in myocardial blood flow using T2 -weighted 3D BOLD imagingMAGNETIC RESONANCE IN MEDICINE, Issue 3 2001Kara B. Wright Abstract The feasibility of detecting regional differences in myocardial blood flow based on the blood oxygen level-dependent (BOLD) effect was evaluated in vivo in dogs (N = 9) using a 3D T2 -prepared segmented gradient-echo sequence at 1.5 T. Regional differences in myocardial blood flow were created by administering adenosine through a catheter placed in the left circumflex coronary artery (LCX). The difference in the R2 (1/T2) relaxation rate between the left ventricular myocardial region supplied by the LCX and regions supplied by the left anterior descending coronary artery (LAD) or septal artery during adenosine administration was correlated to the corresponding regional myocardial blood flow difference determined using fluorescent microspheres. A correlation coefficient of 0.80 was found between the MR BOLD measurements and the myocardial flow assessment. Our results show that the sequence used in this study allows fast 3D BOLD imaging of the heart, and is a promising technique for detecting regional myocardial perfusion differences. Magn Reson Med 46:573,578, 2001. © 2001 Wiley-Liss, Inc. [source] A current perspective of the status of understanding BOLD imaging and its use in studying brain function: a summary of the workshop at the University of North Carolina in Chapel Hill, 26,28 October, 2000NMR IN BIOMEDICINE, Issue 7-8 2001E. Mark Haacke First page of article [source] | ||||||||||