More than BOLD: Dual‐spin populations create functional contrast
| Autor: | David Ress, Elizabeth J. Halfen, Vimal Singh, Jung Hwan Kim, Amanda Taylor, Josef Pfeuffer |
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| Rok vydání: | 2019 |
| Předmět: |
Adult
Male Relaxometry media_common.quotation_subject Population Contrast Media Signal-To-Noise Ratio computer.software_genre Retina Article 030218 nuclear medicine & medical imaging Young Adult 03 medical and health sciences 0302 clinical medicine Nuclear magnetic resonance Voxel Image Processing Computer-Assisted medicine High spatial resolution Humans Contrast (vision) Radiology Nuclear Medicine and imaging education Visual Cortex Spin-½ media_common Cerebral Cortex Physics Brain Mapping education.field_of_study Models Statistical Blood-oxygen-level dependent Middle Aged Magnetic Resonance Imaging Oxygen Blood Visual cortex medicine.anatomical_structure Cerebrovascular Circulation Female computer Algorithms Photic Stimulation 030217 neurology & neurosurgery |
| Zdroj: | Magn Reson Med |
| ISSN: | 1522-2594 0740-3194 |
| Popis: | PURPOSE: Functional magnetic resonance imaging (fMRI) contrast has generally been associated with changes in transverse relaxivity caused by blood oxygen concentration, the so-called blood oxygen-level dependent contrast. However, this interpretation of fMRI contrast has been called into question by several recent experiments at high spatial resolution. Experiments were conducted to examine contrast dependencies that cannot be explained only by differences in relaxivity in a single spin population. METHODS: Measurements of functional signal and contrast were obtained in human early visual cortex during a high-contrast visual stimulation over a large range of echo times and for several flip angles. Small voxels (1.5 mm) were used to restrict the measurements to cortical gray matter in early visual areas identified using retinotopic mapping procedures. RESULTS: Measurements were consistent with models that include two spin populations. The dominant population has a relatively short transverse lifetime that is strongly modulated by activation. However, functional contrast is also affected by volume changes between this short-lived population and the longer-lived population. CONCLUSION: Some of the previously observed “non-classical” behaviors of functional contrast can be explained by these interacting dual-spin populations. |
| Databáze: | OpenAIRE |
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