Noise concerns and post-processing procedures in cerebral blood flow (CBF) and cerebral blood volume (CBV) functional magnetic resonance imaging

The relation between relative cerebral blood flow (relCBF), relative cerebral blood volume (relCBV), and mean transit time (MTT) changes was examined in 20 patients with acute cerebral ischemia (<6 h) using perfusion-weighted magnetic resonance imaging. Regions of interest (ROI) were selected on MTT maps covering the entire MTT abnormal cortical area. These ROIs were transferred to the relCBF and relCBV maps to analyze the relation between relCBF, relCBV, and MTT on a voxel-by-voxel basis. On the unaffected side, a tight coupling of relCBF and relCBV was found with little variation of MTT. In hypoperfused cortex, relCBV was increased at all investigated relCBF categories, and there was greater relCBV variability than on the unaffected side. Only a severe decrease of relCBF, to less than 0.3, in comparison with the unaffected side was associated with a reduction of relCBV less than 1.0. In contrast to the unaffected side, a power law function (relCBV = 2.283 × relCBF0.549) resulted in a better fit than using a linear function for the correlation of relCBF and relCBV. MTT ratios increased steadily with decreasing CBF values. In conclusion, there is a clear relation between different perfusion-weighted magnetic resonance imaging parameters in acute ischemia, reflecting both the degree of hemodynamic failure as well as compensatory mechanisms including vasodilation.

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Functional magnetic resonance imaging

New Oxford Textbook of Psychiatry ◽

10.1093/med/9780199696758.003.0025 ◽

2012 ◽

pp. 196-201 ◽

Cited By ~ 1

Author(s):

E. T. Bullmore ◽

J. Suckling

Keyword(s):

Magnetic Resonance Imaging ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Magnetic Resonance ◽

Functional Magnetic Resonance Imaging ◽

Visual Stimulation ◽

Single Photon ◽

Photon Emission ◽

Functional Magnetic Resonance ◽

Resonance Imaging

Functional magnetic resonance imaging (fMRI) is a relatively new technique for measuring changes in cerebral blood flow. The first fMRI studies, showing functional activation of the occipital cortex by visual stimulation and activation of the motor cortex by finger movement, were published in the early 1990s. In the years since then, fMRI has been used to investigate the physiological response to a wide variety of experimental procedures in both normal human subjects and diverse patient groups. In the next 10 years, fMRI will probably establish a role for itself in radiological and psychiatric practice; currently the clinical role of fMRI is limited to specialized applications such as assessment of hemispheric dominance prior to neurosurgery. The outstanding advantage of fMRI over alternative methods of imaging cerebral blood flow, such as positron emission tomo-graphy (PET) and single-photon emission computed tomography (SPECT), is that it does not involve exposure to radioactivity. This means that a single subject can safely be examined by fMRI on many occasions, and that the ethical problems of examining patients are minimized. Functional MRI also has superior spatial resolution (in the order of millimetres) and temporal resolution (in the order of seconds) compared with PET and SPECT. In this chapter, we provide an introduction to technical issues relevant to fMRI data acquisition, study design, and analysis. An introduction to the basic physical principles of magnetization and nuclear magnetic resonance, and the technology, is given in Chapter 2.3.7. Many excellent specialist texts covering all aspects of functional magnetic resonance imaging are available for the reader seeking more detailed treatment of the issues.

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Measurements of BOLD/CBV Ratio Show Altered fMRI Hemodynamics during Stroke Recovery in Rats

Journal of Cerebral Blood Flow & Metabolism ◽

10.1038/sj.jcbfm.9600084 ◽

2005 ◽

Vol 25 (7) ◽

pp. 820-829 ◽

Cited By ~ 38

Author(s):

Young R Kim ◽

In J Huang ◽

Seong-Ryong Lee ◽

Emiri Tejima ◽

Joseph B Mandeville ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Magnetic Resonance ◽

Functional Magnetic Resonance Imaging ◽

Somatosensory Cortex ◽

Blood Volume ◽

Cerebral Blood Volume ◽

Focal Cerebral Ischemia ◽

Stroke Recovery ◽

Functional Magnetic Resonance ◽

Resonance Imaging

Brain responses to external stimuli after permanent and transient ischemic insults have been documented using cerebral blood volume weighted (CBVw) functional magnetic resonance imaging (fMRI) in correlation with tissue damage and neurological recovery. Here, we extend our previous studies of stroke recovery in rat models of focal cerebral ischemia by comparing blood oxygen level-dependent (BOLD) and cerebral blood volume (CBV) changes. Responses to forepaw stimulation were measured in normal rats ( n = 5) and stroke rats subjected to 2 h of middle cerebral artery occlusion ( n = 6). Functional magnetic resonance imaging was performed 2 weeks after stroke to evaluate the recovery process. After stroke, animals showed variable degrees of fMRI activation in ipsilesional cortex, the extent of which did not correlate with structural damages as measured using apparent diffusion coefficient, fractional anisotropy, blood volume, and vessel size index. While the contralesional cortex showed good overlap between BOLD and CBV-activated regions, the ipsilesional cortex showed low covariance between significantly activated voxels by BOLD and CBVw techniques. In particular, the relative activation during contralateral stimuli in the ipsilesional somatosensory cortex was significantly higher for CBVw responses than BOLD, which might be due to stroke-related alterations in fMRI hemodynamic coupling. Aberrant subcortical activations were also observed. When unaffected forelimbs were stimulated, strong bilateral responses were observed. However, little thalamic responses accompanied stimulation of affected forelimbs despite significant activation in the ipsilesional somatosensory cortex. These results suggest that stroke affects not only local hemodynamics and coupling but also other factors including neural connectivity.

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Temporal Patterns of Uncoupling Between Oxidative Metabolism and Regional Cerebral Blood Flow Demonstrated by Functional Magnetic Resonance Imaging

Investigative Radiology ◽

10.1097/00004424-199511000-00001 ◽

1995 ◽

Vol 30 (11) ◽

pp. 625-633 ◽

Cited By ~ 7

Author(s):

PETER HEDERA ◽

DEE WU ◽

JONATHAN S. LEWIN ◽

DAVID MILLER ◽

ALAN J. LERNER ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Magnetic Resonance ◽

Functional Magnetic Resonance Imaging ◽

Oxidative Metabolism ◽

Regional Cerebral Blood Flow ◽

Functional Magnetic Resonance ◽

Resonance Imaging ◽

Regional Cerebral Blood

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Assessment of cerebral blood flow reserve using functional magnetic resonance imaging

Journal of Magnetic Resonance Imaging ◽

10.1002/jmri.1880060504 ◽

1996 ◽

Vol 6 (5) ◽

pp. 718-725 ◽

Cited By ~ 25

Author(s):

Peter Hedera ◽

Song Lai ◽

Jonathan S. Lewin ◽

E. Mark Haacke ◽

Dee Wu ◽

...

Keyword(s):

Magnetic Resonance Imaging ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Magnetic Resonance ◽

Functional Magnetic Resonance Imaging ◽

Functional Magnetic Resonance ◽

Resonance Imaging ◽

Flow Reserve

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Functional Magnetic Resonance Imaging Measures of Blood Flow Patterns in the Human Auditory Cortex in Response to Sound

Journal of Speech Language and Hearing Research ◽

10.1044/jslhr.4103.538 ◽

1998 ◽

Vol 41 (3) ◽

pp. 538-548 ◽

Cited By ~ 7

Author(s):

Sean C. Huckins ◽

Christopher W. Turner ◽

Karen A. Doherty ◽

Michael M. Fonte ◽

Nikolaus M. Szeverenyi

Keyword(s):

Magnetic Resonance Imaging ◽

Blood Flow ◽

Magnetic Resonance ◽

Functional Magnetic Resonance Imaging ◽

Functional Magnetic Resonance ◽

Resonance Imaging ◽

Speech Stimuli ◽

Complex Stimuli ◽

Scanning Session ◽

Auditory Research

Functional Magnetic Resonance Imaging (fMRI) holds exciting potential as a research and clinical tool for exploring the human auditory system. This noninvasive technique allows the measurement of discrete changes in cerebral cortical blood flow in response to sensory stimuli, allowing determination of precise neuroanatomical locations of the underlying brain parenchymal activity. Application of fMRI in auditory research, however, has been limited. One problem is that fMRI utilizing echo-planar imaging technology (EPI) generates intense noise that could potentially affect the results of auditory experiments. Also, issues relating to the reliability of fMRI for listeners with normal hearing need to be resolved before this technique can be used to study listeners with hearing loss. This preliminary study examines the feasibility of using fMRI in auditory research by performing a simple set of experiments to test the reliability of scanning parameters that use a high resolution and high signal-to-noise ratio unlike that presently reported in the literature. We used consonant-vowel (CV) speech stimuli to investigate whether or not we could observe reproducible and consistent changes in cortical blood flow in listeners during a single scanning session, across more than one scanning session, and in more than one listener. In addition, we wanted to determine if there were differences between CV speech and nonspeech complex stimuli across listeners. Our study shows reproducibility within and across listeners for CV speech stimuli. Results were reproducible for CV speech stimuli within fMRI scanning sessions for 5 out of 9 listeners and were reproducible for 6 out of 8 listeners across fMRI scanning sessions. Results of nonspeech complex stimuli across listeners showed activity in 4 out of 9 individuals tested.

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