Qin Q, Grgac K, van Zijl PCDetermination of whole-brain oxygen extraction fractions by fast measurement of blood T(2) in the jugular vein. Magn Reson Med 65:471-479

The Russell H. Morgan Department of Radiology and Radiological Science, Division of MR Research, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA.
Magnetic Resonance in Medicine (Impact Factor: 3.57). 02/2011; 65(2):471-9. DOI: 10.1002/mrm.22556
Source: PubMed


The oxygen extraction fraction of the brain reports on the balance between oxygen delivery and consumption and can be used to assess deviations in physiological homeostasis. This is relevant clinically as well as for calibrating blood oxygen level-dependent functional MRI responses. Oxygen extraction fraction is reflected in the arteriovenous difference in oxygen saturation fraction (Y(v) - Y(a) ), which can be determined from venous T(2) values when arterial oxygenation is known. A pulse sequence is presented that allows rapid measurement (<1 min) of blood T(2) s in the internal jugular vein. The technique combines slice-saturation and blood inflow to attain high signal-to-noise ratio in blood and minimal contamination from tissue. The sequence is sensitized to T(2) using a nonselective Carr-Purcell-Meiboom-Gill T(2) preparation directly after slice saturation. Fast scanning (pulse repetition time of about 2 sec) is possible by using a nonselective saturation directly after acquisition to rapidly achieve steady-state longitudinal magnetization. The venous T(2) (for 10 msec Carr-Purcell-Meiboom-Gill interecho time) for normal volunteers was 62.4 ± 6.1 msec (n = 20). A calibration curve relating T(2) to blood oxygenation was established using a blood perfusion phantom. Using this calibration, a whole-brain oxygen extraction fraction of 0.37 ± 0.04 was determined (n = 20), in excellent agreement with literature values.

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    • "In the absence of pathology or abnormal physiology, the OEF tends to be very similar across all brain regions; this implies that variations in oxygen demand are generally accounted for by concurrent variations in blood supply. MRI techniques have been developed that measure a " whole brain " or global value for the OEF (Huppert et al., 2009; Lu and Ge, 2008; Qin et al., 2011; Van Zijl et al., 1998; Xu et al., 2009), which is valuable in healthy subjects and for developing or validating FMRI methods. However, in the presence of compromised vasculature, brain injury or tumours, these methods do not provide the regional information required for detailed diagnoses. "
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    ABSTRACT: Functional magnetic resonance imaging typically measures signal increases arising from changes in the transverse relaxation rate over small regions of the brain and associates these with local changes in cerebral blood flow, blood volume and oxygen metabolism. Recent developments in pulse sequences and image analysis methods have improved the specificity of the measurements by focussing on changes in blood flow or changes in blood volume alone. However, FMRI is still unable to match the physiological information obtainable from positron emission tomography (PET), which is capable of quantitative measurements of blood flow and volume, and can indirectly measure resting metabolism. The disadvantages of PET are its cost, its availability, its poor spatial resolution and its use of ionising radiation. The MRI techniques introduced here address some of these limitations and provide physiological data comparable with PET measurements. We present an 18-minute MRI protocol that produces multi-slice whole-brain coverage and yields quantitative images of resting cerebral blood flow, cerebral blood volume, oxygen extraction fraction, CMRO(2), arterial arrival time and cerebrovascular reactivity of the human brain in the absence of any specific functional task. The technique uses a combined hyperoxia and hypercapnia paradigm with a modified arterial spin labelling sequence.
    Full-text · Article · Dec 2011 · NeuroImage
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    • "Therefore, the effects from the baseline parameter variations are expected to be magnified for the stimulation period, especially from Y v base . Fortunately , this parameter can be measured in a few minutes with some recently developed MRI techniques (Lu and Ge, 2008; Qin et al, 2011), which is recommended for future experiments to minimize the influence from the intersubject variation in Y v base . "
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    ABSTRACT: The poststimulus blood oxygenation level-dependent (BOLD) undershoot has been attributed to two main plausible origins: delayed vascular compliance based on delayed cerebral blood volume (CBV) recovery and a sustained increased oxygen metabolism after stimulus cessation. To investigate these contributions, multimodal functional magnetic resonance imaging was employed to monitor responses of BOLD, cerebral blood flow (CBF), total CBV, and arterial CBV (CBV(a)) in human visual cortex after brief breath hold and visual stimulation. In visual experiments, after stimulus cessation, CBV(a) was restored to baseline in 7.9±3.4 seconds, and CBF and CBV in 14.8±5.0 seconds and 16.1±5.8 seconds, respectively, all significantly faster than BOLD signal recovery after undershoot (28.1±5.5 seconds). During the BOLD undershoot, postarterial CBV (CBV(pa), capillaries and venules) was slightly elevated (2.4±1.8%), and cerebral metabolic rate of oxygen (CMRO(2)) was above baseline (10.6±7.4%). Following breath hold, however, CBF, CBV, CBV(a) and BOLD signals all returned to baseline in ∼20 seconds. No significant BOLD undershoot, and residual CBV(pa) dilation were observed, and CMRO(2) did not substantially differ from baseline. These data suggest that both delayed CBV(pa) recovery and enduring increased oxidative metabolism impact the BOLD undershoot. Using a biophysical model, their relative contributions were estimated to be 19.7±15.9% and 78.7±18.6%, respectively.
    Full-text · Article · Apr 2011 · Journal of cerebral blood flow and metabolism: official journal of the International Society of Cerebral Blood Flow and Metabolism
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    ABSTRACT: A simple method of measuring baseline cerebrospinal fluid volume fraction (V(CSF) ) in three-dimensional is proposed that used the characteristic of cerebrospinal fluid with very long T(2) . It is based on the fitting of monoexponential decay of only cerebrospinal fluid signal, using a nonselective T(2) preparation scheme. Three-dimensional gradient- and spin-echo acquisition also improves signal-to-noise ratio efficiency and brain coverage. Both V(CSF) and T(2,CSF) are fitted voxel by voxel and analyzed in different cortical areas across subjects. V(CSF) is largely regionally dependent (occipital: 8.9 ± 1.7%, temporal: 11.4 ± 2.4%, and frontal: 21.4 ± 6.9%). Measured T(2,CSF) was 1573 ± 146 msec within cortical lobes as compared with 2062 ± 37 msec from ventricle regions. Different parameter set were compared, and the robustness of the new method is demonstrated. Conversely, when comparing with the proposed approach, large overestimation of segmentation based method using T(1) -weighted images is found, and the underlying causes are suggested.
    No preview · Article · Feb 2011 · Magnetic Resonance in Medicine
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