Impact of depression status on myocardial oxygenation: An oxygenation-sensitive magnetic resonance imaging study with breathing maneuvers
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Angiology
Depression
Blood oxygenation
Experimental data up to 7.0 T show that the blood oxygenation level-dependent (BOLD) signal of functional magnetic resonance imaging (fMRI) increases with higher magnetic field strength. Although several studies at 11.7 T report higher BOLD signal compared with studies at 7.0 T, no direct comparison at these two field strengths has been performed under the exact same conditions. It therefore remains unclear whether the expected increase of BOLD effect with field strength will still continue to hold for fields >7.0 T. To examine this issue, we compared the BOLD activation signal at 7.0 and 11.7 T with the two common sequences, spin-echo (SE) and gradient-echo (GE) echo planar imaging (EPI). We chose the physiologically well controlled rat model of electrical forepaw stimulation under medetomidine sedation. While a linear to superlinear increase in activation with field strengths up to 7.0 T was reported in the literature, we observed no significant activation difference between 7.0 and 11.7 T with either SE or GE. Discussing the results in light of the four-component model of the BOLD signal, we showed that at high field only two extravascular contributions remain relevant, while both intravascular components vanish. Constancy of the BOLD effect is discussed due to motional narrowing, i.e., susceptibility gradients become so strong that phase variance of diffusing spins decreases and therefore the BOLD signal also decreases. This finding will be of high significance for the planning of future human and animal fMRI studies at high fields and their quantitative analysis.
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Blood-oxygen-level dependent
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Background: Brain functional magnetic resonance imaging (fMRI) is sensitive to changes in blood oxygenation level dependent (BOLD) brain magnetic states. The fMRI scanner produces a complex-valued image, but the calculation of the original BOLD magnetic source is not a mathematically tractable problem. We conduct numeric simulations to understand the BOLD fMRI model.
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Functional MRI(fMRI) has been one of the most important techniques for human brain function analyses. In this paper, we will review the research development in the fMRI analyses of depression patients' brain function,especially for using blood oxygenation level dependent fMRI to discuss the depression patients ' different brain regions.
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Depression
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Human brain
Functional Imaging
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A central question in the analysis of functional magnetic resonance imaging (IMRI) data is whether the measured fMRI signal summates in a linear fashion over repeated inputs. Most fMRI studies collect images sensitive to blood-oxygenation-level dependent (BOLD) contrast, which measures the local amount of deoxygenated hemoglobin (dHb). When neurons are active, more oxygenated hemoglobin is supplied than is needed for their metabolic demands, resulting in a decrease in dHb and an increase in MR signal. For analysis of fMRI data, researchers must therefore create experimental hypotheses of the measurable BOLD response based upon the predicted neuronal activity. An influential early model of the fMRI BOLD response assumes that BOLD activity is a linear transformation of neuronal input, representing the filtering effects of the vascular system. Recent studies have called this interpretation into question, due to observed differences in the pattern of linearity across brain regions that serve distinct functions.
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Blood-oxygen-level dependent
Deoxygenated Hemoglobin
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Blood oxygenation
Brain mapping
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When neural activity increases in a region of the brain, the local magnetic resonance signal produced in that part of the brain increases by a small amount owing to changes in blood oxygenation. This blood oxygenation level dependent (BOLD) effect is the basis for most functional magnetic resonance imaging (fMRI) studies done today to map patterns of activation in the working human brain. In this tutorial we will review the main techniques used to analyze fMRI data.
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Neural Activity
Blood-oxygen-level dependent
Human brain
Brain mapping
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Blood oxygenation
Blood-oxygen-level dependent
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Functional magnetic resonance imaging(fMRI) is the newest technology in the field of brain functional imaging.It has been applied in basic area,and gradually used in clinic.Especially,the investigation of blood oxygenation level dependent fMRI(BOLD-fMRI) in neurology and psychiatry developed quickly.It's summarized in this article.
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Blood-oxygen-level dependent
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Functional magnetic resonance imaging can be used to study the networks of neurons that underline different behaviors. The blood oxygenation level-dependent signal though, measures the activity averaged across heterogeneous population of neurons with different response characteristics. It is therefore often impossible to infer the properties of the underlying imaged neural populations by simply examining the fMRI signal. Here, we describe the use of an adaptation paradigm to study the properties of neuronal populations beyond the spatial resolution of fMRI.
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