Abstract 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 decrease blood deoxyhemoglobin concentration and an oxygenation. Images highlighting areas enhancement temporally correlated to are created. © 1992 Academic Press, Inc.

Abstract Image processing strategies for functional magnetic resonance imaging (FMRI) data sets acquired using a gradient‐recalled echo‐planar sequence are considered. The analysis is carried out the mathematics of vector spaces. Data consisting N sequential images same slice brain tissue analyzed in time‐domain and also, after Fourier transformation, frequency domain. A technique thresholding introduced that uses shape response pixel compared with reference waveform as decision criterion....

A biomechanical model is presented for the dynamic changes in deoxyhemoglobin content during brain activation. The incorporates conflicting effects of both blood oxygenation and volume. Calculations based on show pronounced transients level dependent (BOLD) signal measured with functional MRI, including initial dips overshoots a prolonged poststimulus undershoot BOLD signal. Furthermore, these transient can occur presence tight coupling cerebral flow oxygen metabolism throughout activation...

Abstract Recently, several implementations of arterial spin labeling (ASL) techniques have been developed for producing MRI images sensitive to local tissue perfusion. For quantitation perfusion, both pulsed and continuous methods potentially suffer from a number systematic errors. In this study, general kinetic model the ASL signal is described that can be used assess these With appropriate assumptions, reduces models previously analyze data, but also provides way errors result if...

Functional magnetic resonance imaging (FMRI) is a new, noninvasive tool thought to measure changes related regional cerebral blood flow (rCBF). Previous FMRI studies have demonstrated functional within the primary cortex in response simple activation tasks, but it unknown whether can also detect nonprimary complex mental activities. We therefore scanned six right-handed healthy subjects while they performed self-paced and finger movements with right left hands. Some tasks at fixed rate (2...

The cerebellum traditionally has been viewed as a neural device dedicated to motor control. Although recent evidence shows that it is involved in nonmotor operations well, an important question whether this involvement independent of control and guidance. Functional magnetic resonance imaging was used demonstrate attention performance independently activate distinct cerebellar regions. These findings support broader concept function, which the diverse cognitive noncognitive neurobehavioral...

In the pulsed arterial spin labeling (ASL) techniques EPISTAR, PICORE, and FAIR, subtraction of two images in which inflowing blood is first tagged then not yields a qualitative map perfusion. An important reason this quantitative that there spatially varying delay transit from tagging region to imaging slice cannot be measured single subtraction. We introduce here modifications ASL (QUIPSS QUIPSS II) avoid problem by applying additional saturation pulses control time duration bolus,...

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 results despite large differences static tissue contrast. Two major sources systematic error measurement identified: transit delay from region slice; inclusion intravascular tagged signal. A modified technique called QUIPSS II is described that...

Quantitative imaging of perfusion using a single subtraction, second version (QUIPSS II) is pulsed arterial spin labeling (ASL) technique for improving the quantitation by minimizing two major systematic errors: variable transit delay from distal edge tagged region to slices, and contamination intravascular signal blood that flows through slices. However, residual errors remain due incomplete saturation spins over slab-shaped QUIPSS II pulse, spatial mismatch inversion slice profiles. By...

Abstract Magnetic resonance imaging methods recently demonstrated regional cerebral signal changes in response to limb movement and visual stimulation, attributed blood flow enhancement. We studied 5 normal subjects scanned while listening auditory stimuli including nonspeech noise, meaningless speech sounds, single words, narrative text. Imaged regions included the lateral aspects of both hemispheres. Signal superior temporal gyrus sulcus were observed bilaterally all subjects. Speech...

Abstract In this study, Blood Oxygenation Level Dependent (BOLD) contrast in the detection of human brain activation was compared between spin‐echo and gradient‐echo echo‐planar sequences at 1.5 T. Time course series images containing primary motor cortex were collected during rest (no finger movement) (finger movement). Each time using a different TE . Resting active state signal intensities each measured identical regions cortex. From these data, resting R 2 (1/ T ) values obtained. Across...

THIRTEEN normal volunteers were studied with fMRI during arithmetic performance after a night of sleep and following deprivation (SD). Aims included determining whether the prefrontal cortex (PFC) parietal lobe areas are vulnerable to effects SD. After sleep, activation localized bilateral PFC, lobes premotor areas. Following SD, activity in these regions decreased markedly, especially PFC. Performance also dropped. Data from serial subtraction task consistent Horne's PFC vulnerability...

Abstract Under ideal conditions, continuous arterial spin labeling (ASL) techniques are higher in SNR than pulsed ASL by a factor of e. Presented here is direct theoretical and experimental comparison ASL, using versions both that amenable to multislice imaging insensitive variations transit times (continuous with delay before imaging, QUIPSS II (Quantitative Imaging Perfusion Using Single Subtraction–second version)). image quality for comparable time was nearly identical single‐slice...

Abstract In pathologies in which slow or collateral flow conditions may exist, conventional arterial spin labeling (ASL) methods that apply magnetic tags based on the location of spins not provide robust measures cerebral blood (CBF), as transit delay for delivery to target tissues far exceed relaxation time tag. Here we describe current ASL with velocity‐selective (VS) (termed VSASL) do require spatial selectivity and can thus quantitative CBF under conditions. The implementation a...

Abstract A new signal‐to‐noise ratio (SNR) efficient method is introduced for the mapping of vascular territories based on pseudocontinuous arterial spin labeling (ASL). tagging pulse train modified using additional transverse gradient pulses and phase cycling to place some arteries in a tag condition, while others passing through same plane are control condition. This combined with Hadamard or similar encoding scheme such that all vessels interest fully inverted relaxed nearly cycles,...

Abstract We present, here, a simple method for measurement and correction of off‐resonance related geometric distortion in echo‐planar imaging (EP1). This uses high signal‐to‐noise ratio (SNR) EPI‐based field maps, rapidly acquired using series gradient recalled images collected across range TE values. map is distorted the same manner as EPI to be unwarped, providing direct look‐up table correct location each pixel data. adds very little scan time robust easy implement.

Functional magnetic resonance imaging (fMRI) is capable of detecting task-induced blood oxygenation changes using susceptibility sensitive pulse sequences such as gradient-recalled echo-planar (EPI). The local signal increases seen in the time course are believed to be due an increase oxygen delivery that incommensurate with demands. To help isolate sources functional changes, authors have incorporated various forms diffusion weighting into EPI characterize apparent mobility functionally...

FUNCTIONAL magnetic resonance imaging (fMRI) was used to explore the brain substrate associated with global and local processing of visuospatial patterns. Systematic differences in activation, consistent observed reaction time data collected under conditions visual hemifield presentation, were found occipitotemporal regions right left hemispheres. Within hemisphere, area activation fractional signal changes greater than conditions. In input high comparable.