Issues of spectral quality in clinical <sup>1</sup>H‐magnetic resonance spectroscopy and a gallery of artifacts

Kreis, Roland

doi:10.1002/nbm.891

Cited by 401 publications

(385 citation statements)

References 76 publications

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“…Reported SNR values were calculated in the time domain (free induction decay, FID), by dividing the signal amplitude of the fitted metabolite (GABA or creatine) in the time domain by the standard deviation (SD) of the noise at the end (last 15%) of the acquired FID signal. This is done to obtain a metric for SNR that is independent of line shape 38. SNR was calculated for both coil setups; as spectral resolution of the GABA resonance was similar for both setups, the SNR gain was quantified as the ratio of the two SNR values.…”

Section: Methodsmentioning

confidence: 99%

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

et al. 2018

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The combination of functional MRI (fMRI) and MRS is a promising approach to relate BOLD imaging to neuronal metabolism, especially at high field strength. However, typical scan times for GABA edited spectroscopy are of the order of 6‐30 min, which is long compared with functional changes observed with fMRI.The aim of this study is to reduce scan time and increase GABA sensitivity for edited spectroscopy in the human visual cortex, by enlarging the volume of activated tissue in the primary visual cortex. A dedicated setup at 7 T for combined fMRI and GABA MRS is developed. This setup consists of a half volume multi‐transmit coil with a large screen for visual cortex activation, two high density receive arrays and an optimized single‐voxel MEGA‐sLASER sequence with macromolecular suppression for signal acquisition.The coil setup performance as well as the GABA measurement speed, SNR, and stability were evaluated. A 2.2‐fold gain of the average SNR for GABA detection was obtained, as compared with a conventional 7 T setup. This was achieved by increasing the viewing angle of the participant with respect to the visual stimulus, thereby activating almost the entire primary visual cortex, allowing larger spectroscopy measurement volumes and resulting in an improved GABA SNR. Fewer than 16 signal averages, lasting 1 min 23 s in total, were needed for the GABA fit method to become stable, as demonstrated in three participants. The stability of the measurement setup was sufficient to detect GABA with an accuracy of 5%, as determined with a GABA phantom. In vivo, larger variations in GABA concentration are found: 14‐25%. Overall, the results bring functional GABA detections at a temporal resolution closer to the physiological time scale of BOLD cortex activation.

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Section: Methodsmentioning

confidence: 99%

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

et al. 2018

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“…However, often the limited field of view of surface coils does not include these anatomical landmarks, making it necessary to identify bifurcations of vessels and nerves as landmarks. Since the density of methylene protons in pure adipose tissue or bone marrow is about 10 4 times higher than that of IMCL methylene protons in skeletal muscle, the acquisition of spectra needs either efficient suppression of signals from outside the selected voxel (82,108) or suppression of voxels with fat by subsequent post processing in chemical shift imaging (69,109). Slotboom et al (110) suggested a fitting procedure that uses time domain models to fit frequency domain spectra, a method called TDFDFIT.…”

Section: Calibration By the Creatine Signalmentioning

confidence: 99%

“…In obese patients with more prominent EMCL signals, the additional separation of the two resonances of IMCL and EMCL may determine the success or failure of the automatic fitting algorithms (108,110). As a rule of thumb, fitting algorithms need at least a clear dip between the two resonance lines in order to be able to separate them reliably.…”

Section: Influence Of Magnetic Field Strength On 1 H-mr Spectra Of Skmentioning

confidence: 99%

Role of proton MR for the study of muscle lipid metabolism

et al. 2006

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1 H-MR spectroscopy (MRS) of intramyocellular lipids (IMCL) became particularly important when it was recognized that IMCL levels are related to insulin sensitivity. While this relation is rather complex and depends on the training status of the subjects, various other influences such as exercise and diet also influence IMCL concentrations. This may open insight into many metabolic interactions; however, it also requires careful planning of studies in order to control all these confounding influences. This review summarizes various historical, methodological, and practical aspects of 1 H-MR spectroscopy (MRS) of muscular lipids. That includes a differentiation of bulk magnetic susceptibility effects and residual dipolar coupling that can both be observed in MRS of skeletal muscle, yet affecting different metabolites in a specific way. Fitting of the intra-(IMCL) and extramyocellular (EMCL) signals with complex line shapes and the transformation into absolute concentrations is discussed. Since the determination of IMCL in muscle groups with oblique fiber orientation or in obese subjects is still difficult, potential improvement with high-resolution spectroscopic imaging or at higher field strength is considered. Fat selective imaging is presented as a possible alternative to MRS and the potential of multinuclear MRS is discussed. 1 H-MRS of muscle lipids allows non-invasive and repeated studies of muscle metabolism that lead to highly relevant findings in clinics and patho-physiology.

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“…In addition to the three books and the paper mentioned above, it is worth reading a recent paper that describes and explains several types of artifacts that may interfere with spectral interpretation (5). A book by de Graaf provides an excellent explanation of the theory, language and technical aspects of in vivo NMR spectroscopy (6).…”

Section: Building a Useful Reference Librarymentioning

confidence: 99%

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

2006

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The purpose of this paper is to facilitate the comparison of magnetic resonance (MR) spectra acquired from unknown brain lesions with published spectra in order to help identify unknown lesions in clinical settings. The paper includes lists of references for published MR spectra of various brain diseases, including pyogenic abscesses, encephalitis (herpes simplex, Rasmussen's and subacute sclerosing panencephalitis), neurocysticercosis, tuberculoma, cysts (arachnoid, epidermoid and hydatid), acute disseminated encephalomyelitis (ADEM), adrenoleukodystrophy (ALD), Alexander disease, Canavan's disease, Krabbe disease (globoid cell leukodystrophy), Leigh's disease, megalencephalic leukoencephalopathy with cysts, metachromatic leukodystrophy (MLD), Pelizaeus-Merzbacher disease, Zellweger syndrome, HIV-associated lesions [cryptococcus, lymphoma, toxoplasmosis and progressive multifocal leukoencephalopathy (PML)], hydrocephalus and tuberous sclerosis. Each list includes information on the echo time(s) (TE) of the published spectra, whether a control spectrum is shown, whether the corresponding image and voxel position are shown and the patient ages if known. The references are listed in the approximate order of usefulness, based on spectral quality, number of spectra, range of echo times and whether the voxel positions are shown. Spectra of Zellweger syndrome, cryptococcal infection, toxoplasmosis and lymphoma are included, along with a spectrum showing propanediol (propylene glycol).

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Issues of spectral quality in clinical ¹H‐magnetic resonance spectroscopy and a gallery of artifacts

Cited by 401 publications

References 76 publications

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

Role of proton MR for the study of muscle lipid metabolism

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

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Issues of spectral quality in clinical 1H‐magnetic resonance spectroscopy and a gallery of artifacts

Cited by 401 publications

References 76 publications

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

Maximizing sensitivity for fast GABA edited spectroscopy in the visual cortex at 7 T

Role of proton MR for the study of muscle lipid metabolism

Identification of diffuse and focal brain lesions by clinical magnetic resonance spectroscopy

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Issues of spectral quality in clinical ¹H‐magnetic resonance spectroscopy and a gallery of artifacts