다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

https://www.cell.com/cell-metabolism/pdf/S1550-4131(11)00420-7.pdf

Brain energy metabolism: focus on astrocyte-neuron metabolic cooperation

Proton NMR chemical shift and J-coupling values are presented for 35 metabolites that can be detected by in vivo or in vitro NMR studies of mammalian brain. Measurements were obtained using high-field NMR spectra of metabolites in solution, under conditions typical for normal physiological temperature and pH. This information is presented with an accuracy that is suitable for computer simulation of metabolite spectra to be used as basis functions of a parametric spectral analysis procedure. This procedure is verified by the analysis of a rat brain extract spectrum, using the measured spectral parameters. In addition, the metabolite structures and example spectra are presented, and clinical applications and MR spectroscopic measurements of these metabolites are reviewed.

http://pfeifer.phas.ubc.ca/refbase/files/Govindaraju-NMRBiomed-2000-13-129.pdf

Proton NMR chemical shifts and coupling constants for brain metabolites.

Functional brain imaging with positron emission tomography and magnetic resonance imaging has been used extensively to map regional changes in brain activity. The signal used by both techniques is based on changes in local circulation and metabolism (brain work). Our understanding of the cell biology of these changes has progressed greatly in the past decade. New insights have emerged on the role of astrocytes in signal transduction as has an appreciation of the unique contribution of aerobic glycolysis to brain energy metabolism. Likewise our understanding of the neurophysiologic processes responsible for imaging signals has progressed from an assumption that spiking activity (output) of neurons is most relevant to one focused on their input. Finally, neuroimaging, with its unique metabolic perspective, has alerted us to the ongoing and costly intrinsic activity within brain systems that most likely represents the largest fraction of the brain's functional activity.

Brain Work and Brain Imaging

Continuing improvements in analytical technology along with an increased interest in performing comprehensive, quantitative metabolic profiling, is leading to increased interest pressures within the metabolomics community to develop centralized metabolite reference resources for certain clinically important biofluids, such as cerebrospinal fluid, urine and blood. As part of an ongoing effort to systematically characterize the human metabolome through the Human Metabolome Project, we have undertaken the task of characterizing the human serum metabolome. In doing so, we have combined targeted and non-targeted NMR, GC-MS and LC-MS methods with computer-aided literature mining to identify and quantify a comprehensive, if not absolutely complete, set of metabolites commonly detected and quantified (with today's technology) in the human serum metabolome. Our use of multiple metabolomics platforms and technologies allowed us to substantially enhance the level of metabolome coverage while critically assessing the relative strengths and weaknesses of these platforms or technologies. Tables containing the complete set of 4229 confirmed and highly probable human serum compounds, their concentrations, related literature references and links to their known disease associations are freely available at http://www.serummetabolome.ca.

/pdf/the-human-serum-metabolome-52a86bwnf3.pdf

The Human Serum Metabolome

The prefrontal cortex is a common target brain structure in psychiatry and neuroscience due to its role in working memory and cognitive control. Large differences in magnetic susceptibility between the air-filled sinuses and the tissue/bone in the frontal part of the human head cause a strong and highly localized magnetic field focus in the prefrontal cortex. As a result, image distortion and signal dropout are observed in MR imaging. A set of external electrical coils is presented that provides localized and high-amplitude shim fields in the prefrontal cortex, with minimum impact on the rest of the brain when combined with regular zero- to second-order spherical harmonics shimming. The experimental realization of the new shim method strongly minimized or even eliminated signal dropout in gradient-echo images acquired at settings typically used in functional magnetic resonance at 4 T.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/mrm.22164

Magnetic field homogenization of the human prefrontal cortex with a set of localized electrical coils.

Optimization of static magnetic field homogeneity in the human and animal brain in vivo.

Purpose To determine the reproducibility of a comprehensive single-session measurement of glutathione (GSH), γ-aminobutyric acid (GABA), glutamate, and other biochemicals implicated in the pathophysiology of multiple sclerosis (MS) in the human brain with 1 H magnetic resonance spectroscopy (MRS). Materials and methods Five healthy subjects were studied twice in separate 1-hour sessions at 7T. One MS patient was also scanned once. GSH and GABA were measured with J-difference editing using a semilocalized by adiabatic selective refocusing sequence (semi-LASER, TE = 72 msec). A stimulated echo acquisition mode sequence (STEAM, TE = 10 msec) was used to detect glutamate along with the overall biochemical profile. Spectra were quantified with LCModel. Quantification accuracy was assessed through Cramer-Rao lower bounds (CRLB). Reproducibility of the metabolite quantification was tested using coefficients of variation (CoV). Results CRLB were ≤7% for GSH, GABA, and glutamate and average CoV of 7.8 ± 3.2%, 9.5 ± 7.0%, and 3.2 ± 1.7% were achieved, respectively. The average test/retest concentration differences at this measurement reproducibility and quantification accuracy were smaller for GABA and glutamate than intersubject variations in metabolite content with CoV ratios of 0.6 and 0.8, respectively. As proof of principle, GSH, GABA, and glutamate were also detected in an MS patient. Conclusion GSH, GABA, glutamate, and other metabolites relevant in MS can be quantified at 7T with high accuracy and reproducibility in a single 1-hour session. This methodology might serve as a clinical research tool to investigate biochemical markers associated with MS. Level of evidence 2 J. Magn. Reson. Imaging 2017;45:187-198.

/pdf/reproducibility-measurement-of-glutathione-gaba-and-12f60l8ihg.pdf

Reproducibility measurement of glutathione, GABA, and glutamate: Towards in vivo neurochemical profiling of multiple sclerosis with MR spectroscopy at 7T.

Dynamic shim updating (DSU) of the zero- to second-order spherical harmonic field terms has previously been shown to improve the magnetic field homogeneity in the human brain at 4 Tesla. The increased magnetic field inhomogeneity at 7 Tesla can benefit from inclusion of third-order shims during DSU. However, pulsed higher-order shims can generate a multitude of temporally varying magnetic fields arising from eddy-currents that can strongly degrade the magnetic field homogeneity.The first realization of zero- to third-order DSU with full preemphasis and B(0) compensation enabled improved shimming of the human brain at 7 Tesla not only in comparison with global (i.e. static) shimming, but also when compared to state-of-the-art zero- to second-order DSU. Temporal shim-to-shim interactions were measured for each of the 16 zero- to third-order shim coils along 1D column projections on a spherical phantom. The decomposition into up to 3 exponentials allowed full preemphasis and B(0) compensation of all 16 shims covering 67 potential shim-to-shim interactions. Despite the significant improvements achievable with DSU, the magnetic field homogeneity is still not perfect even when updating all zero- through third-order shims. This is because DSU is still inherently limited by the shallowness of the low order spherical harmonic fields and their inability to compensate the higher-order inhomogeneities encountered in vivo. However, DSU maximizes the usefulness of conventional shim coil systems and provides magnetic field homogeneity that is adequate for a wide range of applications.

/pdf/dynamic-shimming-of-the-human-brain-at-7-tesla-11t5mamxsg.pdf

Dynamic Shimming of the Human Brain at 7 Tesla

Adiabatic pulses are amplitude- and frequency-modulated pulses that are insensitive to the effects of B1-inhomogeneity and frequency offset. From the classical adiabatic passage experiments, the adiabatic condition is derived and analyzed. From the adiabatic condition, amplitude and frequency modulation functions are derived and optimized over predetermined radio frequency amplitude and frequency offset ranges. Description of the selective inversion and refocusing properties of adiabatic full-passage pulses leads to the principle of plane rotation pulses, of which the BIR-4 (B1-insensitive rotation) pulse will be discussed in detail. Theoretical simulations based on the Bloch equations, three-dimensional vector diagrams, and experimental applications demonstrate the utility and performance of the adiabatic pulses for in vivo NMR and for liquid state high-resolution NMR. ©1997 John Wiley & Sons, Inc. Concepts Magn Reson 9: 247–268, 1997

Robin A. de Graaf

Papers

Magnetic field homogenization of the human prefrontal cortex with a set of localized electrical coils.

Optimization of static magnetic field homogeneity in the human and animal brain in vivo.

Reproducibility measurement of glutathione, GABA, and glutamate: Towards in vivo neurochemical profiling of multiple sclerosis with MR spectroscopy at 7T.

Dynamic Shimming of the Human Brain at 7 Tesla

Adiabatic rf pulses: applications to in vivo NMR