Field mapping without reference scan using asymmetric echo-planar techniques

Gruetter, Rolf; Tkáč, Ivan

doi:10.1002/(sici)1522-2594(200002)43:2<319::aid-mrm22>3.0.co;2-1

Cited by 545 publications

(474 citation statements)

References 15 publications

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“…3). First-and second-order shims were adjusted using FAST(EST)MAP (shim volume = 22 × 25 × 22 mm 3 ) (Gruetter, 1993;Gruetter and Tkac, 2000). Flip angles of the water suppression pulses were optimized to reduce the residual water peak height below that of NAA.…”

Section: Mr Protocolmentioning

confidence: 99%

Are glutamate and lactate increases ubiquitous to physiological activation? A 1H functional MR spectroscopy study during motor activation in human brain at 7Tesla

Xin²,

et al. 2014

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a b s t r a c t a r t i c l e i n f oRecent studies at high field (7 Tesla) have reported small metabolite changes, in particular lactate and glutamate (below 0.3 μmol/g) during visual stimulation. These studies have been limited to the visual cortex because of its high energy metabolism and good magnetic resonance spectroscopy (MRS) sensitivity using surface coil. The aim of this study was to extend functional MRS (fMRS) to investigate for the first time the metabolite changes during motor activation at 7 T. Small but sustained increases in lactate (0.17 μmol/g ± 0.05 μmol/g, p b 0.001) and glutamate (0.17 μmol/g ± 0.09 μmol/g, p b 0.005) were detected during motor activation followed by a return to the baseline after the end of activation. The present study demonstrates that increases in lactate and glutamate during motor stimulation are small, but similar to those observed during visual stimulation. From the observed glutamate and lactate increase, we inferred that these metabolite changes may be a general manifestation of the increased neuronal activity. In addition, we propose that the measured metabolite concentration increases imply an increase in ΔCMR O2 that is transiently below that of ΔCMR Glc during the first 1 to 2 min of the stimulation.© 2014 Elsevier Inc. All rights reserved. IntroductionFunctional MR spectroscopy (fMRS) provides direct insights into brain metabolism by investigating the metabolic response of the brain to a physiological stimulus. The high spectral resolution and signal-tonoise ratio (SNR) of fMRS at high field (N3 Tesla) improve the accuracy and precision of the quantification of many brain metabolites (Mekle et al., 2009;Tkac et al., 2001Tkac et al., , 2009. In addition to the increased chemical shift dispersion, a high time resolution is of advantage for the characterization of the small transient changes observed. Recent fMRS studies (Lin et al., 2012;Mangia et al., 2007b;Schaller et al., 2013) at high field (7 Tesla) reported small metabolite concentration changes during visual stimulation (around 0.2 μmol/g). In particular, a very small lactate concentration increase between 10 and 23% has been observed. Recently, functional diffusion-weighted MRS has been used to investigate metabolite ADC changes as a potential consequence of micro structural changes during activation (Branzoli et al., 2013).The lactate increase observed during visual stimulation has been suggested to explain the mismatch of cerebral metabolic rate of change for glucose (ΔCMR Glc ) (or cerebral blood flow, CBF) and cerebral metabolic rate of change for oxygen (ΔCMR O2 ) during brain activation. However, many studies have reported different results concerning the transient mismatch of ΔCMR Glc , CBF and ΔCMR O2 during functional activity (reviewed in Buxton (2010)). The characterization of these changes has been reported in positron emission tomography (PET) (Fox and

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Section: Mr Protocolmentioning

confidence: 99%

Are glutamate and lactate increases ubiquitous to physiological activation? A 1H functional MR spectroscopy study during motor activation in human brain at 7Tesla

Xin²,

et al. 2014

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“…The mouse brain was positioned in the isocenter of the magnet and located with fast-spin-echo images with repetition time of 4 seconds, echo time of 52 ms, and echo train length of 8. Field homogeneity in the region of interest was achieved with FAST(EST)MAP (Gruetter, 1993;Gruetter and Tkác, 2000). Volumes of interest were placed in the hippocampus Fig.…”

Section: Mrsmentioning

confidence: 99%

Longitudinal neurochemical modifications in the aging mouse brain measured in vivo by 1H magnetic resonance spectroscopy

Duarte

Gruetter

2014

Neurobiology of Aging

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H MRS Brain Metabolism a b s t r a c tAlterations to brain homeostasis during development are reflected in the neurochemical profile determined noninvasively by 1 H magnetic resonance spectroscopy. We determined longitudinal biochemical modifications in the cortex, hippocampus, and striatum of C57BL/6 mice aged between 3 and 24 months . The regional neurochemical profile evolution indicated that aging induces general modifications of neurotransmission processes (reduced GABA and glutamate), primary energy metabolism (altered glucose, alanine, and lactate) and turnover of lipid membranes (modification of choline-containing compounds and phosphorylethanolamine), which are all probably involved in the frequently observed age-related cognitive decline. Interestingly, the neurochemical profile was different in male and female mice, particularly in the levels of taurine that may be under the control of estrogen receptors. These neurochemical profiles constitute the basal concentrations in cortex, hippocampus, and striatum of healthy aging male and female mice.

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“…The cardiac trigger was typically send 50 or 60 ms after the maximum observed blood pressure. Cardiac triggered and respiratory gated shimming was performed to reduce the localized proton line width in a myocardial voxel of 4 × 5 × 5 mm 3 to 20-30 Hz using a triggered FASTESTMAP sequence [41], resulting in a non-localized proton line width of 80-120 Hz. The spectrometer was triggered to start acquisition at the beginning of the automated injection process.…”

Section: In Vivo Mri and Mrsmentioning

confidence: 99%

Direct noninvasive estimation of myocardial tricarboxylic acid cycle flux in vivo using hyperpolarized 13C magnetic resonance

Bastiaansen

Tian

Lei

et al. 2015

Journal of Molecular and Cellular Cardiology

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Background: The heart relies on continuous energy production and imbalances herein impair cardiac function directly. The tricarboxylic acid (TCA) cycle is the primary means of energy generation in the healthy myocardium, but direct noninvasive quantification of metabolic fluxes is challenging due to the low concentration of most metabolites. Hyperpolarized 13 C magnetic resonance spectroscopy (MRS) provides the opportunity to measure cellular metabolism in real time in vivo. The aim of this work was to noninvasively measure myocardial TCA cycle flux (V TCA ) in vivo within a single minute. Methods and results: Hyperpolarized [1-13 C]acetate was administered at different concentrations in healthy rats. 13C incorporation into [1-13 C]acetylcarnitine and the TCA cycle intermediate [5-13 C]citrate was dynamically detected in vivo with a time resolution of 3 s. Different kinetic models were established and evaluated to determine the metabolic fluxes by simultaneously fitting the evolution of the 13 C labeling in acetate, acetylcarnitine, and citrate. V TCA was estimated to be 6.7 ± 1.7 μmol · g −1 · min −1 (dry weight), and was best estimated with a model using only the labeling in citrate and acetylcarnitine, independent of the precursor. The TCA cycle rate was not linear with the citrate-to-acetate metabolite ratio, and could thus not be quantified using a ratiometric approach. The 13 C signal evolution of citrate, i.e. citrate formation was independent of the amount of injected acetate, while the 13 C signal evolution of acetylcarnitine revealed a dose dependency with the injected acetate. The 13 C labeling of citrate did not correlate to that of acetylcarnitine, leading to the hypothesis that acetylcarnitine formation is not an indication of mitochondrial TCA cycle activity in the heart. Conclusions: Hyperpolarized [1-13 C]acetate is a metabolic probe independent of pyruvate dehydrogenase (PDH) activity. It allows the direct estimation of V TCA in vivo, which was shown to be neither dependent on the administered acetate dose nor on the 13 C labeling of acetylcarnitine. Dynamic 13 C MRS coupled to the injection of hyperpolarized [1-13 C]acetate can enable the measurement of metabolic changes during impaired heart function.

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Field mapping without reference scan using asymmetric echo-planar techniques

Cited by 545 publications

References 15 publications

Are glutamate and lactate increases ubiquitous to physiological activation? A 1H functional MR spectroscopy study during motor activation in human brain at 7Tesla

Are glutamate and lactate increases ubiquitous to physiological activation? A 1H functional MR spectroscopy study during motor activation in human brain at 7Tesla

Longitudinal neurochemical modifications in the aging mouse brain measured in vivo by 1H magnetic resonance spectroscopy

Direct noninvasive estimation of myocardial tricarboxylic acid cycle flux in vivo using hyperpolarized 13C magnetic resonance

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