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A biomechanical model is presented for the dynamic changes in deoxyhemoglobin content during brain activation. The model incorporates the conflicting effects of dynamic changes in both blood oxygenation and blood volume. Calculations based on the model show pronounced transients in the deoxyhemoglobin content and the blood oxygenation level dependent (BOLD)(More)
Image processing strategies for functional magnetic resonance imaging (FMRI) data sets acquired using a gradient-recalled echo-planar imaging sequence are considered. The analysis is carried out using the mathematics of vector spaces. Data sets consisting of N sequential images of the same slice of brain tissue are analyzed in the time-domain and also,(More)
In the pulsed arterial spin labeling (ASL) techniques EPISTAR, PICORE, and FAIR, subtraction of two images in which inflowing blood is first tagged and then not tagged yields a qualitative map of perfusion. An important reason this map is not quantitative is that there is a spatially varying delay in the transit of blood from the tagging region to the(More)
We investigated the cortical mechanisms of visual-spatial attention while subjects discriminated patterned targets within distractor arrays. Functional magnetic resonance imaging (fMRI) was used to map the boundaries of retinotopic visual areas and to localize attention-related changes in neural activity within several of those areas, including primary(More)
Quantitative imaging of perfusion using a single subtraction, second version (QUIPSS II) is a pulsed arterial spin labeling (ASL) technique for improving the quantitation of perfusion imaging by minimizing two major systematic errors: the variable transit delay from the distal edge of the tagged region to the imaging slices, and the contamination by(More)
The blood-oxygen-level-dependent (BOLD) signal measured in the brain with functional magnetic resonance imaging (fMRI) during an activation experiment often exhibits pronounced transients at the beginning and end of the stimulus. Such transients could be a reflection of transients in the underlying neural activity, or they could result from transients in(More)
We describe here experimental considerations in the implementation of quantitative perfusion imaging techniques for functional MRI using pulsed arterial spin labeling. Three tagging techniques: EPISTAR, PICORE, and FAIR are found to give very similar perfusion results despite large differences in static tissue contrast. Two major sources of systematic error(More)
Using gradient-echo echo-planar MRI, a local signal increase of 4.3 +/- 0.3% is observed in the human brain during task activation, suggesting a local decrease in blood deoxyhemoglobin concentration and an increase in blood oxygenation. Images highlighting areas of signal enhancement temporally correlated to the task are created.
This review provides a summary statement of recommended implementations of arterial spin labeling (ASL) for clinical applications. It is a consensus of the ISMRM Perfusion Study Group and the European ASL in Dementia consortium, both of whom met to reach this consensus in October 2012 in Amsterdam. Although ASL continues to undergo rapid technical(More)
An issue in blood oxygenation level dependent contrast-based functional MRI is the accurate interpretation of the activation-induced signal changes. Hemodynamic factors other than activation-induced changes in blood oxygenation are known to contribute to the signal change magnitudes and dynamics, and therefore need to be accounted for or removed. In this(More)