Time‐domain combination of MR spectroscopy data acquired using phased‐array coils

Brown, Mark

doi:10.1002/mrm.20244

Cited by 88 publications

(142 citation statements)

References 9 publications

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“…Briefly, the 8-channel phased-array coil data recorded were combined into single regular time-domain free-induction decay signals, using a C-language computer program that implemented a previously published algorithm (Brown, 2004), with the unsuppressed voxel tissue water signal from each receiver coil element providing the required relative array coil sensitivities. The two resulting free-induction decay signals for the editing pulses on/off scans were subtracted in the time domain to yield the difference signal, which was filtered with an exponential multiplication function corresponding to a 5-Hz linebroadening and then Fourier-transformed to obtain the GABA and Glx spectra (Figure 1b).…”

Section: H Mrs Data Processing and Quantificationmentioning

confidence: 99%

Investigation of Cortical Glutamate–Glutamine and γ-Aminobutyric Acid in Obsessive–Compulsive Disorder by Proton Magnetic Resonance Spectroscopy

Simpson

Shungu

Bender

et al. 2012

Neuropsychopharmacol

124

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Glutamatergic abnormalities in corticostriatal brain circuits are thought to underlie obsessive-compulsive disorder (OCD). Whether these abnormalities exist in adults with OCD is not clear. We used proton magnetic resonance spectroscopy ( 1 H MRS) to test our hypothesis that unmedicated adults with OCD have reduced glutamate plus glutamine (Glx) levels in the medial prefrontal cortex (MPFC) compared with healthy controls. Levels of g-aminobutyric acid (GABA) were also explored. Twenty-four unmedicated adults with OCD and 22 matched healthy control subjects underwent 1 H MRS scans at 3.0 T. Resonances of both Glx and GABA were obtained using the standard J-editing technique and assessed as ratios relative to voxel tissue water (W) in the MPFC (the region of interest) and the dorsolateral prefrontal cortex (DLPFC) to explore the regional specificity of any finding. In the MPFC, Glx/W did not differ by diagnostic group (p ¼ 0.98) or sex (p ¼ 0.57). However, GABA/W was decreased in OCD (2.16 ± 0.46 Â 10 À3 ) compared with healthy controls (2.43 ± 0.45 Â 10 À3 , p ¼ 0.045); moreover, age of OCD onset was inversely correlated with MPFC GABA/W (r ¼ À0.50, p ¼ 0.015). MPFC GABA/W was higher in females than in males. In the DLPFC, there were no main effects of diagnosis or gender on Glx/W or GABA/W. These data indicate that unmedicated adults with OCD do not have Glx abnormalities in a MPFC voxel that includes the pregenual anterior cingulate cortex. However, they may have decreased MPFC GABA levels. How GABA abnormalities might contribute to corticostriatal dysfunction in OCD deserves further study.

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Section: H Mrs Data Processing and Quantificationmentioning

confidence: 99%

Investigation of Cortical Glutamate–Glutamine and γ-Aminobutyric Acid in Obsessive–Compulsive Disorder by Proton Magnetic Resonance Spectroscopy

Simpson

Shungu

Bender

et al. 2012

Neuropsychopharmacol

124

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“…24 A comparison of the performance of many of these CSI methods has been provided by Pohmann et al 43 Barker and Lin 26 have an excellent discussion of methods that use multireceiver arrays (e.g., an eightchannel head array) to accelerate CSI acquisitions, similar to the methods used in parallel imaging. An added complication is that, although there have been descriptions of algorithms 44,45 used in combining CSI spectra obtained from each individual coil element, few of these are routinely available on commercial whole-body clinical scanners. This situation is in contrast to multicoil MR imaging and parallel imaging, in which this combination (or acceleration, or both) is performed routinely.…”

Section: Spatial Localizationmentioning

confidence: 99%

Recent Advances in Magnetic Resonance Neurospectroscopy

Rosen

Lenkinski

2007

Neurotherapeutics

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Summary:Over the past two decades, proton magnetic resonance spectroscopy (proton MRS) of the brain has made the transition from research tool to a clinically useful modality. In this review, we first describe the localization methods currently used in MRS studies of the brain and discuss the technical and practical factors that determine the applicability of the methods to particular clinical studies. We also describe each of the resonances detected by localized solvent-suppressed proton MRS of the brain and discuss the metabolic and biochemical information that can be derived from an analysis of their concentrations. We discuss spectral quantitation and summarize the reproducibility of both single-voxel and multivoxel methods at 1.5 and 3-4 T. We have selected three clinical neurologic applications in which there has been a consensus as to the diagnostic value of MRS and summarize the information relevant to clinical applications. Finally, we speculate about some of the potential technical developments, either in progress or in the future, that may lead to improvements in the performance of proton MRS.

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“…Better results are obtained by weighting the spectra according to the reference peak amplitudes (3) or SNRs (7), which approximate a matched filter. When performing 1 H spectroscopy in vivo, particularly reliable reference peak data are obtained by repeating the experiment without water suppression since tissue contains water at $40 M concentration (8)(9)(10)(11). Alternatively, one can use the whole chemical shift range of the spectra.…”

Section: Existing Approaches To Receive Array Mr Spectroscopymentioning

confidence: 99%

“…Alternatively, one can use the whole chemical shift range of the spectra. Brown (8) suggested scaling and phasing each spectrum by the first point in its FID, i.e., by the mean value of the spectrum. The singular value decomposition (SVD) also uses the whole spectra for combination (9).…”

Section: Existing Approaches To Receive Array Mr Spectroscopymentioning

confidence: 99%

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Receive array magnetic resonance spectroscopy: Whitened singular value decomposition (WSVD) gives optimal Bayesian solution

2010

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Receive array coils play a pivotal role in modern MRI. MR spectroscopy can also benefit from the enhanced signal-tonoise ratio and field of view provided by a receive array. In any experiment using an n-element array, n different complex spectra will be recorded and each spectrum unavoidably contains an undesired noise contribution. Previous algorithms for combining spectra have ignored the fact that the noise detected by different array elements is correlated. We introduce here an algorithm for efficiently, robustly, and automatically combining these n spectra using noise whitening and the singular value decomposition to provide the single combined spectrum that has maximum likelihood in the presence of this correlated noise. Simulations are performed that demonstrate the superiority of this approach to previous methods. Experiments in phantoms and in vivo on the brain, heart, and liver of normal volunteers, at 1.5 T and 3 T, using array coils from eight to 32 elements and with 1 H and 31 P nuclei, validate our approach, which provides signal-to-noise ratio improvements of up to 60% in our tests. The whitening and the singular value decomposition algorithm become most advantageous for large arrays, when the noise is markedly correlated, and when the signal-to-noise ratio is low. Key words: MR spectroscopy; array; coil combination; WSVD; SVD; noise whitening MR spectroscopy provides unique insights into the chemical composition of a subject in a completely noninvasive manner. For example, chemical shift imaging (CSI) and single voxel spectroscopy allow measurement of the concentrations of metabolites containing nuclei such as 1 H and 31 P, offering a window into biochemical processes occurring in vivo. Nevertheless, constraints on the signalto-noise ratio (SNR) obtainable with current technology are one of the primary factors limiting clinical applications of MR spectroscopy. We report our recent work to alleviate this SNR limitation through an improved method for combining the data gathered from receive array coils.Receive array coils have a long history in the MRI community following the work of Hyde et al. (1) and Roemer et al. (2). By replacing the single radiofrequency receive coil in an MR scanner with an array of smaller coils (''array elements''), improvements in SNR are obtained. The smaller size of each of these elements makes them couple more strongly with the magnetization in the subject under examination, giving stronger signals and hence a larger SNR than with a single element coil. Furthermore, although each element has a smaller field of view, the field of view covered by at least one coil may be very large. Thus, when the signals from each element are combined appropriately, a receive array provides data of significantly enhanced SNR that cover a wider field of view. The Roemer et al. (2) founding paper on receive array MRI introduced a widely accepted model of the array detection process, which we use here to allow a unified description of existing methods for receive array combination in MR sp...

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Time‐domain combination of MR spectroscopy data acquired using phased‐array coils

Cited by 88 publications

References 9 publications

Investigation of Cortical Glutamate–Glutamine and γ-Aminobutyric Acid in Obsessive–Compulsive Disorder by Proton Magnetic Resonance Spectroscopy

Investigation of Cortical Glutamate–Glutamine and γ-Aminobutyric Acid in Obsessive–Compulsive Disorder by Proton Magnetic Resonance Spectroscopy

Recent Advances in Magnetic Resonance Neurospectroscopy

Receive array magnetic resonance spectroscopy: Whitened singular value decomposition (WSVD) gives optimal Bayesian solution

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