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Magnetic Resonance Spectroscopy is a technique that has the capability of measuring metabolites in vivo and, in appropriate conditions, to infer its metabolic rates. The success of MRS depends a lot on its sensitivity, which limits the usage of X-nuclei MRS. However, technological developments and refinements in methods have made in vivo heteronuclear MRS possible in humans and in small animals. This chapter provides detailed descriptions of the main procedures needed to perform successful indoi:10.1007/978-1-4939-7531-0_11 pmid:29341009 fatcat:5ir53yrjp5dkrkjonoxfsxrqv4
more »... vo heteronuclear MRS experiments, with a particular focus on experimental setup in 13 C MRS experiments in rodents.
The current study investigates a new model of barrel cortex activation using stimulation of the infraorbital branch of the trigeminal nerve. A robust and reproducible activation of the rat barrel cortex was obtained following trigeminal nerve stimulation. Blood oxygen leveldependent (BOLD) effects were obtained in the primary somatosensory barrel cortex (S1BF), the secondary somatosensory cortex (S2) and the motor cortex. These cortical areas were reached from afferent pathways from thedoi:10.1016/j.mri.2010.02.002 pmid:20399585 fatcat:wair36md5bcmbaxgnun5qyhaqi
more »... al ganglion, the trigeminal nuclei and thalamic nuclei from which neurons project their axons upon whisker stimulation. The maximum BOLD responses were obtained for a stimulus frequency of 1 Hz, a stimulus pulse width of 100 μs and for current intensities between 1.5 and 3 mA. The BOLD response was nonlinear as a function of frequency and current intensity. Additionally, modeling BOLD responses in the rat barrel cortex from separate cerebral blood flow (CBF) and cerebral metabolic rate of oxygen (CMRO 2 ) measurements showed good agreement with the shape and amplitude of measured BOLD responses as a function of stimulus frequency and will potentially allow to identify the sources of BOLD nonlinearities. Activation of the rat barrel cortex using trigeminal nerve stimulation will contribute to the interpretation of the BOLD signals from functional magnetic resonance imaging studies.
Balanced steady-state free precession (bSSFP) can be used as an alternative to gradient-echo (GE) EPI for BOLD functional MRI when image distortions and signal drop-outs are severe such as at ultra-high field. However, 3D-bSSFP acquisitions have distinct drawbacks on either human or animal MR systems. On clinical scanners, 3D imaging is suboptimal for localized fMRI applications, and also results in distortions, blurring, and increased sensitivity to motion or physiological noise. OnarXiv:1812.04395v1 fatcat:4b5vk3f3j5ehno6ncokt4k2xye
more »... l systems, 3D acquisitions have low temporal resolution due to limited acceleration options, while single slice offers insufficient coverage. The aim of the present study was to implement a multi-slice bSSFP acquisition with Cartesian read-out to obtain non-distorted BOLD fMRI activation maps in the human and rat brain at ultra-high field. We show that the bSSFP signal characteristics are preserved in a new pseudo-steady-state. In the human brain at 7 Tesla, we demonstrate that both task- and resting-state fMRI can be performed with 2D-bSSFP, with a temporal SNR that matches that of 3D-bSSFP, resulting in - at least - equal performance. In the rat brain at 14 Tesla, we show that the multi-slice bSSFP protocol has similar sensitivity to gradient-echo EPI for task fMRI, while benefitting from much reduced distortions and drop-outs. The advantages of passband bSSFP at 14 Tesla in comparison with GE-EPI are expected to be even more marked for mouse fMRI.
Gruetter). cycle (Brand et al., 1997; Westergaard et al., 1995; Yudkoff et al., 1988) . ... , 1993; Gruetter and Boesch, 1992) . ... et al., 1998a; Gruetter et al., 2001) . ...doi:10.1016/s0197-0186(02)00034-7 pmid:12020614 fatcat:bzopskui4fhcve2644x7ias63i
., Gruetter, R., 2014. Is the macromolecule signal tissue-specific in healthy human brain? A 1 H MRS study at 7 tesla in the occipital lobe. Magn. Reson. Med. 72, 934-940. 2 0 levetiracetam. ...doi:10.1101/498337 fatcat:u3vy7a6zx5b63eh74ebsaudjvy
In vivo localized and fully adiabatic homonuclear and heteronuclear polarization transfer experiments were designed and performed in the rat brain at 9.4 T after infusion of hyperpolarized sodium [1,2-13 C 2 ] and sodium [1-13 C] acetate. The method presented herein leads to highly enhanced in vivo detection of short-T 1 13 C as well as attached protons. This indirect detection scheme allows for probing additional molecular sites in hyperpolarized substrates and their metabolites and can thusdoi:10.1002/mrm.23231 pmid:22190079 fatcat:rher2p24p5gubhh7x4wtqou6je
more »... ad to improved spectral resolution such as in the case of 13 C-acetate metabolism. Magn Reson Med 68:349-352, 2012. V C 2011 Wiley Periodicals, Inc.
Ivan Tkáč * Rolf Gruetter Center for Magnetic Resonance Research University of Minnesota Minneapolis, Minnesota © 2005 Wiley-Liss, Inc. Magnetic Resonance in Medicine 54:1048 -1049 (2005) ...doi:10.1002/mrm.20658 fatcat:pemqghcuafei7bs2nnhxlwrbim
This work explores a concept for motion detection in brain MR examinations using high channel-count RF coil arrays. It applies ultrashort (<100 msec) free induction decay signals, making use of the knowledge that motion induces variations in these signals when compared to a reference free induction decay signal. As a proof-of-concept, the method was implemented in a standard structural MRI sequence. The stability of the free induction decay-signal was verified in phantom experiments. Humandoi:10.1002/mrm.22797 pmid:21337424 fatcat:k57baqrbtfcoznb4qjpraasvfi
more »... iments demonstrated that the observed variations in the navigator data provide a sensitive measure for detection of relevant and common subject motion patterns. The proposed methodology provides a means to monitor subject motion throughout a MRI scan while causing little or no impact on the sequence timing and image contrast. It could hence complement available motion detection and correction methods, thus further reducing motion sensitivity in MR applications. Magn Reson Med 66:135-143,
Gruetter et al., 1996 Gruetter et al., , 1998 Mason et al., 1992) . ... Therefore, automatic adjustments of these shim terms or even higher-order shim terms (Gruetter, 1993; Gruetter and Boesch, 1992; Gruetter and Tkáč, 2000; Hetherington et al., 2006; Miyasaka et al., 2006 ...doi:10.1016/j.neuroimage.2011.12.038 pmid:22227137 fatcat:6olmq3xi5zdo7aglvdyjw7kbzq
Purpose: Most existing methods for accelerated parallel imaging in MRI require additional data, which are used to derive information about the sensitivity profile of each radiofrequency (RF) channel. In this work, a method is presented to avoid the acquisition of separate coil calibration data for accelerated Cartesian trajectories. Methods: Quadratic phase is imparted to the image to spread the signals in k-space (aka phase scrambling). By rewriting the Fourier transform as a convolutiondoi:10.1002/mrm.25252 pmid:24753087 fatcat:sezgzjuuarg63nhbkufjx7celq
more »... ion, a window can be introduced to the convolved chirp function, allowing a lowresolution image to be reconstructed from phase-scrambled data without prominent aliasing. This image (for each RF channel) can be used to derive coil sensitivities to drive existing parallel imaging techniques. As a proof of concept, the quadratic phase was applied by introducing an offset to the x 2 À y 2 shim and the data were reconstructed using adapted versions of the image space-based sensitivity encoding and GeneRalized Autocalibrating Partially Parallel Acquisitions algorithms. Results: The method is demonstrated in a phantom (1 Â 2, 1 Â 3, and 2 Â 2 acceleration) and in vivo (2 Â 2 acceleration) using a 3D gradient echo acquisition. Conclusion: Phase scrambling can be used to perform parallel imaging acceleration without acquisition of separate coil calibration data, demonstrated here for a 3D-Cartesian trajectory. Further research is required to prove the applicability to other 2D and 3D sampling schemes.
In in vivo 1 H spectroscopy, the signal at 1.32 ppm is usually assigned to lactate. This resonance position is shared with threonine at physiological pH. The similarity of spectral patterns of lactate and threonine renders the separate measurement of either threonine or lactate without and even with editing technically challenging. In this study, the threonine signal was detected using a single-shot multiple-bond editing technique and quantified in vivo in both rat and human brains. A threoninedoi:10.1002/mrm.21492 pmid:18228590 fatcat:cegjodeoafahznxv3l6tv4trhe
more »... concentration was estimated at 0.8 ؎ 0.3 mM (mean ؎ SD, n ؍ 6) in the rat brain and at ϳ0.33 mM in the human brain. Magn Reson Med 59:245-251, 2008.
Mason GF, Gruetter R, Rothman DL, Behar KL, Shulman RG, Novotny EJ. ... FIGURE 7 | 7 Two-compartment model of compartmentalized brain metabolism, as proposed by Gruetter et al. (29). ...doi:10.3389/fendo.2013.00156 pmid:24194729 pmcid:PMC3809570 fatcat:k7adm7rauncqplq75kcovbnoym
Improvements in B 0 mapping and shimming were achieved by measuring the static field information in multiple subsequent echoes generated by an asymmetric echo-planar readout gradient train. With careful compensation, eddy current effects were shown to affect the adjustment of the shim coils minimally. In addition to reducing the time required for field mapping by two-fold, the sensitivity was simultaneously optimized irrespective of the prevalent T* 2 present, thereby minimizing the error ofdoi:10.1002/(sici)1522-2594(200002)43:2<319::aid-mrm22>3.3.co;2-t fatcat:kfgoz52jpradrh3x7mt2fkhb7y
more »... static field measurement to below 0.1 Hz. With adiabatic low flip-angle excitation, the time required for field mapping was below 1 second. Magn Reson Med 43:319 -323, 2000.
Publication in the conference proceedings of EUSIPCO, Lausanne, Switzerland, 2008doi:10.5281/zenodo.41127 fatcat:qy7xhdi4ujb7dfk7qpuxwytziu
First and second order shims were adjusted using FAST(EST)MAP (Gruetter and Tkác, 2000) resulting in water linewidth of 13-15 Hz in a 216 μl (6 × 8 × 4.5 mm 3 ) volume. ...doi:10.1016/j.neuroimage.2013.02.042 pmid:23473934 fatcat:xwi3oqfx7nhstcombbtc2xkfdi
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