Proton MRS and MRSI of the brain without water suppression

Dong, Zhengchao

doi:10.1016/j.pnmrs.2014.12.001

Cited by 25 publications

(53 citation statements)

References 149 publications

(278 reference statements)

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“…This approach to acquire a separate water MRSI can be time-consuming and impractical especially for high resolution MRSI. Recent technical developments provided strategies to shorten or even remove the time consuming separate water reference MRSI scans by using proton-density weighted MRI (Maudsley et al, 2009), by accelerated MRSI using parallel imaging techniques (Birch et al, 2015), by embedding water reference scans within the MRSI data acquisition (Maudsley et al, 2009), or by acquiring MRSI without water suppression (Dong, 2015). Among these approaches, the embedded water reference scans and MRSI without water suppression can provide a reference for metabolite concentrations as well as coil phase information necessary for optimal coil combination of MRSI data when multi-channel receive coils are used.…”

Section: Discussionmentioning

confidence: 99%

B0-adjusted and sensitivity-encoded spectral localization by imaging (BASE-SLIM) in the human brain in vivo

2016

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Spectral Localization by Imaging (SLIM) based magnetic resonance spectroscopy (MRS) provides a new framework that overcomes major limitations of current MRS techniques, which allow only rectangular voxel shapes that do not conform the shapes of brain structures or lesions. However, the restrictive assumption of compartmental homogeneity in SLIM can lead to localization errors, thus its applications have been very limited to date. SLIM-based localization is subject to errors due to inhomogeneous B0 and B1 fields, particularly in organs with complex compartmental geometry including the human brain. The limitations of SLIM were overcome through the development and implementation of B0-Adjusted and Sensitivity-Encoded SLIM (BASE-SLIM) that includes corrections for inhomogeneities of both B0 and B1 fields throughout the volume of interest. In this study, we demonstrate significantly improved localization accuracy in compartments with arbitrary shapes and reliable quantification of metabolite concentrations in gray and white matter of the human brain using the BASE-SLIM technique.

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Section: Discussionmentioning

confidence: 99%

B0-adjusted and sensitivity-encoded spectral localization by imaging (BASE-SLIM) in the human brain in vivo

2016

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“…In order to separate metabolite signals from abundant water signal robustly, in vivo MRS methods require techniques for suppression of the water signal during acquisition and/or post‐processing . The vendor‐provided MRS packages on clinical scanners offer water‐suppressed spectroscopic acquisition techniques as the standard approach . However, the acquisition of a non‐water‐suppressed MRS spectrum is generally required to act as an internal reference for metabolite quantification.…”

Section: Introductionmentioning

confidence: 99%

Non‐water‐suppressed short‐echo‐time magnetic resonance spectroscopic imaging using a concentric ring k‐space trajectory

et al. 2017

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Water‐suppressed MRS acquisition techniques have been the standard MRS approach used in research and for clinical scanning to date. The acquisition of a non‐water‐suppressed MRS spectrum is used for artefact correction, reconstruction of phased‐array coil data and metabolite quantification. Here, a two‐scan metabolite‐cycling magnetic resonance spectroscopic imaging (MRSI) scheme that does not use water suppression is demonstrated and evaluated. Specifically, the feasibility of acquiring and quantifying short‐echo (T E = 14 ms), two‐dimensional stimulated echo acquisition mode (STEAM) MRSI spectra in the motor cortex is demonstrated on a 3 T MRI system. The increase in measurement time from the metabolite‐cycling is counterbalanced by a time‐efficient concentric ring k‐space trajectory. To validate the technique, water‐suppressed MRSI acquisitions were also performed for comparison. The proposed non‐water‐suppressed metabolite‐cycling MRSI technique was tested for detection and correction of resonance frequency drifts due to subject motion and/or hardware instability, and the feasibility of high‐resolution metabolic mapping over a whole brain slice was assessed. Our results show that the metabolite spectra and estimated concentrations are in agreement between non‐water‐suppressed and water‐suppressed techniques. The achieved spectral quality, signal‐to‐noise ratio (SNR) > 20 and linewidth <7 Hz allowed reliable metabolic mapping of five major brain metabolites in the motor cortex with an in‐plane resolution of 10 × 10 mm2 in 8 min and with a Cramér‐Rao lower bound of less than 20% using LCModel analysis. In addition, the high SNR of the water peak of the non‐water‐suppressed technique enabled voxel‐wise single‐scan frequency, phase and eddy current correction. These findings demonstrate that our non‐water‐suppressed metabolite‐cycling MRSI technique can perform robustly on 3 T MRI systems and within a clinically feasible acquisition time.

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“…The L2 method was shown to allow reconstruction of metabolic images even from the LTE‐NWS‐MRSI data with metabolic images generally close to those from the LTE‐WS‐MRSI. Several previous studies have demonstrated the feasibility of in vivo non‐water‐suppression MRSI with metabolite and water signals measured simultaneously . Advantages of this approach include the availability of the full water signal for eddy current correction and use an internal reference for metabolite quantification.…”

Section: Discussionmentioning

confidence: 99%

“…Both software‐ and hardware‐based methods has been proposed to help reduced sideband artifacts . In this study, the LTE‐NWS‐MRSI data were acquired at a long TE of 140 ms, where the sideband artifacts are significantly decreased both due to T 2 decay of water signal and reduced gradient‐associated eddy currents . The L2 method provided excellent water removal for the LTE‐NWS‐MRSI data.…”

Section: Discussionmentioning

confidence: 99%

Water removal in MR spectroscopic imaging with L2 regularization

Lin

Považan

Berrington

et al. 2019

Magnetic Resonance in Med

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Purpose An L2‐regularization based postprocessing method is proposed and tested for removal of residual or unsuppressed water signals in proton MR spectroscopic imaging (MRSI) data recorded from the human brain at 3T. Methods Water signals are removed by implementation of the L2 regularization using a synthesized water‐basis matrix that is orthogonal to metabolite signals of interest in the spectral dimension. Simulated spectra with variable water amplitude and in vivo brain MRSI datasets were used to demonstrate the proposed method. Results were compared with two commonly‐used postprocessing methods for removing water signals. Results The L2 method yielded metabolite signals that were close to true values for the simulated spectra. Residual/unsuppressed water signals in human brain short‐ and long‐echo time MRSI datasets were efficiently removed by the proposed method allowing good quality metabolite maps to be reconstructed with minimized contamination from water signals. Significant differences of the creatine signal were observed between brain long‐echo time MRSI without and with water saturation, attributable to the previously described magnetization transfer effect. Conclusions With usage of a synthesized water matrix generated based on reasonable prior knowledge about water and metabolite resonances, the L2 method is shown to be an effective way to remove water signals from MRSI of the human brain.

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Proton MRS and MRSI of the brain without water suppression

Cited by 25 publications

References 149 publications

B0-adjusted and sensitivity-encoded spectral localization by imaging (BASE-SLIM) in the human brain in vivo

B0-adjusted and sensitivity-encoded spectral localization by imaging (BASE-SLIM) in the human brain in vivo

Non‐water‐suppressed short‐echo‐time magnetic resonance spectroscopic imaging using a concentric ring k‐space trajectory

Water removal in MR spectroscopic imaging with L2 regularization

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