Venous blood effects in spin-echo fMRI of human brain

Oja, Joni M. E.; Gillen, Joseph; Kauppinen, Risto A.; Kraut, Michael A.; Zijl, Peter C.M. van

doi:10.1002/(sici)1522-2594(199910)42:4<617::aid-mrm1>3.0.co;2-q

Cited by 97 publications

(70 citation statements)

References 45 publications

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“…better localized to the cortex, a result that is in accordance with those previously obtained by Thulborn et al (1997) in the visual cortex at 3 T. This does not exclude the possibility that some voxels which contain larger blood vessels will give significant signal changes in signal intensity in SE-EPI as a result of the changes in T 2 , as found by Prinster et al (1997) and Oja et al (1999). If necessary the signal from these vessels could be removed by the application of a mild diffusion weighting (Boxerman et al, 1995) at the cost of a further reduction in sensitivity.…”

Section: Discussionsupporting

confidence: 85%

“…However, the T 2 of venous blood decreases significantly faster than that of gray matter with increasing field strength (Wright et al, 1991), so it is to be expected that the relative importance of the first mechanism will increase substantially with increasing B 0 . This has been substantiated in a number of experiments, which have shown that at 1.5 T T 2 -weighted BOLD is either exclusively (Oja et al, 1999) or primarily due to intravascular signal changes (Jones, 1999), whereas at 9.4 T the intravascular contribution is negligible (Lee et al, 1999). It is clear that signal both from larger blood vessels and from the parynchema can be seen in T 2 -weighted BOLD imaging (Prinster et al, 1997); however, in a previous study performed at 3 T it was possible to show an improved spatial resolution in the visual cortex compared to T* 2 -weighted imaging (Thulborn et al, 1997).…”

Section: Introductionmentioning

confidence: 70%

“…The quality of functional contrast obtained with T 2 -weighted imaging differs from that of T* 2 -weighted images in that all contributions from static dephasing are eliminated. This considerably reduces the magnitude of the signal change that can be obtained, and for this reason T 2 -weighted BOLD imaging has to date found limited use, being confined to functional studies of the primary cortices (Bandettini et al, 1994;Constable et al, 1994;Thulborn et al, 1997;Jones et al, 1998;Jones, 1999;Oja et al, 1999;Lee et al, 1999;Lowe et al, 2000) or to signal changes resulting from physiological stress (Prinster et al, 1997;van Zijl et al, 1998;Kavec et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

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An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

et al. 2002

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This study examines the value of spin-echo-based fMRI for cognitive studies at the main magnetic field strength of 3 T using a spin-echo EPI (SE-EPI) sequence and a Stroop color-word matching task. SE-EPI has the potential advantage over conventional gradient-echo EPI (GE-EPI) that signal losses caused by dephasing through the slice are not present, and hence although image distortion will be the same as for an equivalent GE-EPI sequence, signal voids will be eliminated. The functional contrast in SE-EPI will be lower than for GE-EPI, as static dephasing effects do not contribute. As an auxiliary experiment interleaved diffusion-weighted and non-diffusion-weighted SE-EPI was performed in the visual cortex to further elucidate the mechanims of functional contrast. In the Stroop experiment activation was detected in all areas previously found using GE-EPI. Additional frontopolar and ventral frontomedian activations were also found, which could not be detected using GE-EPI. The experiments from visual cortex indicated that at 3 T the BOLD signal change has contributions from the extravascular space and larger blood vessels in roughly equal amounts. In comparison with GE-EPI the absence of static dephasing effects would seem to result in a superior intrinsic spatial resolution. In conclusion the sensitivity of SE-EPI at 3 T is sufficient to make it the method of choice for fMR studies that require a high degree of spatial localization or where the requirement is to detect activation in regions affected by strong susceptibility gradients. © 2002 Elsevier Science (USA)

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Section: Discussionsupporting

confidence: 85%

Section: Introductionmentioning

confidence: 70%

Section: Introductionmentioning

confidence: 99%

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An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

et al. 2002

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“…A positive correlation between ␣ and 0 would suggest that the vessels can expand to a greater extent when the baseline value of the blood flow is lower. A similar conclusion was drawn by Oja et al (28), who reevaluated the original experimental data of the dependence of the blood volume on the blood flow by Grubb et al (22). In the case of a lower baseline, also the percentage change of the inflow could be higher if a certain level of blood flow has to be reached for adequate oxygen delivery.…”

Section: Discussionsupporting

confidence: 63%

“…Another way of reducing the degrees of freedom would be to incorporate the knowledge of biophysical relations between the fitting parameters. This work provides first qualitative relations between the fitting parameters which are in a reasonable range (6,8,10,28). We found that the parameters needed to fit the BOLD response differ, dependent on the shape of the poststimulus undershoot.…”

Section: Discussionmentioning

confidence: 78%

A qualitative test of the balloon model for BOLD‐based MR signal changes at 3T

Mildner¹,

Norris²,

Schwarzbauer³

et al. 2001

Magn. Reson. Med.

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The aim of this study was to adapt the balloon model for BOLDbased MR signal changes to a magnetic field strength of 3T and to examine its validity. The simultaneous measurement of BOLD and diffusion-weighted BOLD responses was performed. The amplitude of the BOLD peak was found to be similar for all subjects when a short visual stimulus of 6 sec was used. The rise-time to the BOLD peak and the shape and depth of the poststimulus undershoot varied significantly. A fit of the experimental BOLD responses was found to be possible by use of parameters within a reasonable physiological range. The relations between these parameters and their influence on the modeled BOLD responses is discussed. A prediction of the balloon model is the occurrence of a BOLD overshoot, i.e., a lag between the changes of the blood volume and the blood flow after the start of the stimulation. Functional MRI is based on measuring the local changes in the blood oxygenation level dependent (BOLD) contrast that occur as a consequence of neuronal activation in the brain (1-3). The change in the MR signal is determined by alterations in the concentration of paramagnetic deoxyhemoglobin, which modifies the effective transverse relaxation time T* 2 . Increases in oxygen consumption and blood volume lead to an increase in the deoxyhemoglobin content and hence to a decreased MR signal, whereas increases in blood flow have the opposite effect (4). Although considerable progress has been made in measuring the changes in oxygen consumption (5-7), blood volume (8,9), and cerebral blood flow (6,10,11), the transient response in the BOLD signal is still not completely understood. It can be divided into three intervals: the fast response (12-15), during which the signal change is negative, the period of elevated signal, and the poststimulus undershoot (3). In order to understand the origins of these signal changes it is desirable to relate the BOLD signal directly to the relevant physiological parameters.The most prominent approach developed to date for modeling the BOLD signal under nonsteady-state conditions is given by the balloon model of Buxton et al. (10). Based on the experimental work of Mandeville et al. (8), who showed that changes in blood volume occur subsequent to changes in blood flow, it considers the vasculature contributing to the BOLD signal as a swelling balloon. The basis of the model is a differential equation system for the blood volume and the total deoxyhemoglobin content, combined with an expression for the total signal change. The results of simulations for the intra-and extravascular signal contributions (16,17) and the oxygen limitation model (18) were used in order to derive time courses for the BOLD signal response.In order to study the time courses of the deoxyhemoglobin concentration and the blood volume in detail it is advantageous if the contributions of the intra-and extravascular spaces can be evaluated separately. This may be achieved by using a weak diffusion weighting to suppress the signal from the intravascular comp...

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Quantitative differentiation between BOLD models in fMRI

et al. 2001

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Several gradient‐echo fMRI blood oxygenation level‐dependent (BOLD) effects are described in the literature: extravascular spin dephasing around capillaries and veins, intravascular phase changes, and transverse relaxation changes of blood. This work considers a series of tissue compartmentalized models incorporating each of these effects, and tries to determine the model which is most consistent with the data. To isolate the different tissue contributions, a series of multi‐echo inversion recovery (IR) fMRI scans were performed. Visual stimulation experiments were performed at 1.5 T, one interleaved six‐echo and two IR six‐echo EPI scans (the latter to suppress gray matter (GM) and cerebrospinal fluid (CSF)). The tissue and vascular composition of activated areas was analyzed using independent spin‐echo IR MRI experiments and MR venography, respectively. This information was used to fit the multi‐echo fMRI data to the BOLD models. The activated areas almost always included a venous vessel visible on the venogram and consisted of GM and CSF. The fMRI signal changes were best described by extravascular dephasing effects in both GM and CSF around a venous vessel, in combination with intravascular effects. The role of spin dephasing around capillaries in GM appears to be insignificant. Magn Reson Med 45:233–246, 2001. © 2001 Wiley‐Liss, Inc.

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Venous blood effects in spin-echo fMRI of human brain

Cited by 97 publications

References 45 publications

An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

An Investigation of the Value of Spin-Echo-Based fMRI Using a Stroop Color–Word Matching Task and EPI at 3 T

A qualitative test of the balloon model for BOLD‐based MR signal changes at 3T

Quantitative differentiation between BOLD models in fMRI

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