Magnetic resonance imaging of blood vessels at high fields: <i>In vivo</i> and <i>in vitro</i> measurements and image simulation

Ogawa, Satoshi; Lee, Tso-Ming

doi:10.1002/mrm.1910160103

Cited by 488 publications

(302 citation statements)

References 4 publications

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“…In the second part of the data analysis, regions of interest (ROIs) over gray matter and draining veins, detectable at the image resolution employed, were identified. Veins were recognized from the anatomic image and the T* 2 -weighted images in which they appeared dark (5,15). The ROIs for the two field strengths were matched by selecting the same sagittal slice for the studies at both fields and using anatomic landmarks for the location of the ROIs (see Fig.…”

Section: Data Processingmentioning

confidence: 99%

Imaging brain function in humans at 7 Tesla

Yacoub

Shmuel

Pfeuffer

et al. 2001

Magnetic Resonance in Med

422

333

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This article describes experimental studies performed to demonstrate the feasibility of BOLD fMRI using echo-planar imaging (EPI) at 7 T and to characterize the BOLD response in humans at this ultrahigh magnetic field. Visual stimulation studies were performed in normal subjects using high-resolution multishot EPI sequences. Changes in R* 2 arising from visual stimulation were experimentally determined using fMRI measurements obtained at multiple echo times. The results obtained at 7 T were compared to those at 4 T. Experimental data indicate that fMRI can be reliably performed at 7 T and that at this field strength both the sensitivity and spatial specificity of the BOLD response are increased. This study suggests that ultrahigh field MR systems are advantageous for functional mapping in humans. Magn Reson Med 45:588 -594, 2001.

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Section: Data Processingmentioning

confidence: 99%

Imaging brain function in humans at 7 Tesla

Yacoub

Shmuel

Pfeuffer

et al. 2001

Magnetic Resonance in Med

422

333

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“…One such example is partially deoxygenated venous blood (1)(2)(3). Other examples include clot (paramagnetic), calcium (diamagnetic) (4), and iron-laden tissue (5), and air/tissue interfaces.…”

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confidence: 99%

Susceptibility weighted imaging (SWI)

Haacke¹,

Xu²,

Cheng³

et al. 2004

Magnetic Resonance in Med

1,460

1,228

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Susceptibility differences between tissues can be utilized as a new type of contrast in MRI that is different from spin density, T 1 -, or T 2 -weighted imaging. Signals from substances with different magnetic susceptibilities compared to their neighboring tissue will become out of phase with these tissues at sufficiently long echo times (TEs). Thus, phase imaging offers a means of enhancing contrast in MRI. Specifically, the phase images themselves can provide excellent contrast between gray matter (GM) and white matter (WM), iron-laden tissues, venous blood vessels, and other tissues with susceptibilities that are different from the background tissue. Also, for the first time, projection phase images are shown to demonstrate tissue (vessel) continuity. In this work, the best approach for combining magnitude and phase images is discussed. The phase images are high-pass-filtered and then transformed to a special phase mask that varies in amplitude between zero and unity. This mask is multiplied a few times into the original magnitude image to create enhanced contrast between tissues with different susceptibilities.

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“…hence decreasing the concentration of deoxyhaemoglobin in capillaries and veins (Rostrup et 10 al., 1995). This leads to an increase in the transverse relaxation time (T 2 * ) of blood in vessels 11 and the surrounding tissue, and thus a global increase in the BOLD-MRI signal (Losert et al,12 2002, Ogawa and Lee, 1990). focal invasive electrode recordings (rat whisker studies (Lindauer et al, 2003)).…”

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confidence: 99%

The effect of isocapnic hyperoxia on neurophysiology as measured with MRI and MEG

Croal¹,

Hall²,

Driver³

et al. 2015

NeuroImage

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. (2015) The effect of isocapnic hyperoxia on neurophysiology as measured with MRI and MEG. NeuroImage, 105 . pp. 323-331. ISSN 1053-8119 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/29395/1/NeuroImage_Croal_Hyperoxia%20and%20the %20resting-state%20brain.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the Creative Commons Attribution Non-commercial No Derivatives licence and may be reused according to the conditions of the licence. For more details see: http://creativecommons.org/licenses/by-nc-nd/2.5/ A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. The physiological effect of hyperoxia has been poorly characterised, with studies reporting 2 conflicting results on the role of hyperoxia as a vasoconstrictor. It is not clear whether 3 hyperoxia is the primary contributor to vasoconstriction or whether induced changes in CO 2 4 that commonly accompany hyperoxia are a factor. As calibrated BOLD fMRI based on 5 hyperoxia becomes more widely used, it is essential to understand the effects of oxygen on 6 resting cerebral physiology. This study used a RespirAct TM system to deliver a repeatable 7 isocapnic hyperoxia stimulus to investigate the independent effect of O 2 on cerebral 8 physiology, removing any potential confounds related to altered CO 2 . T 1 -independent Phase 9Contrast MRI was used to demonstrate that isocapnic hyperoxia has no significant effect on 10 carotid blood flow (normoxia 201 ± 11 ml/min, -0.3 ± 0.8 % change during hyperoxia, p = 11 0.8), whilst Look Locker ASL was used to demonstrate that there is no significant change in 12 arterial cerebral blood volume (normoxia 1.3 ± 0.4 %, -0.5 ± 5 % change during hyperoxia). 13These are in contrast to significant changes in blood flow observed for hypercapnia (6.8 ± 141.5 %/mmHg CO 2 ). In addition, magnetoencephalography provided a method to monitor the 15 effect of isocapnic hyperoxia on neuronal oscillatory power. In response to hyperoxia, a 16 significant focal decrease in oscillatory power was observed across the alpha, beta and low 17 gamma bands in the occipital lobe, compared to a more global significant decrease on 18 hypercapnia. This work suggests that isocapnic hyperoxia provides a more reliable stimulus 19 than hypercapnia for calibrated BOLD, and that previous reports of vasoconstriction during 20 hyperoxia probably reflect the effects of hyperoxia-induced changes in CO 2 . However, 21 hyperoxia does induce changes in oscillatory power consistent with an increase in vigilance, 22 but these changes are smaller than those observed under hypercapnia. The effect of thi...

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Magnetic resonance imaging of blood vessels at high fields: In vivo and in vitro measurements and image simulation

Cited by 488 publications

References 4 publications

Imaging brain function in humans at 7 Tesla

Imaging brain function in humans at 7 Tesla

Susceptibility weighted imaging (SWI)

The effect of isocapnic hyperoxia on neurophysiology as measured with MRI and MEG

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