GLORIA

GEOMAR Library Ocean Research Information Access

X

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Online Resource
    Online Resource
    Metabolite-cycled density-weighted concentric rings k-space trajectory (DW-CRT) enables high-resolution 1 H magnetic resonance spectroscopic imaging at 3-Tesla
    Springer Science and Business Media LLC ; 2018
    In:  Scientific Reports Vol. 8, No. 1 ( 2018-05-17)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 8, No. 1 ( 2018-05-17)
    Abstract: Magnetic resonance spectroscopic imaging (MRSI) is a promising technique in both experimental and clinical settings. However, to date, MRSI has been hampered by prohibitively long acquisition times and artifacts caused by subject motion and hardware-related frequency drift. In the present study, we demonstrate that density weighted concentric ring trajectory (DW-CRT) k-space sampling in combination with semi-LASER excitation and metabolite-cycling enables high-resolution MRSI data to be rapidly acquired at 3 Tesla. Single-slice full-intensity MRSI data (short echo time (TE) semi-LASER TE = 32 ms) were acquired from 6 healthy volunteers with an in-plane resolution of 5 × 5 mm in 13 min 30 sec using this approach. Using LCModel analysis, we found that the acquired spectra allowed for the mapping of total N-acetylaspartate (median Cramer-Rao Lower Bound [CRLB] = 3%), glutamate+glutamine (8%), and glutathione (13%). In addition, we demonstrate potential clinical utility of this technique by optimizing the TE to detect 2-hydroxyglutarate (long TE semi-LASER, TE = 110 ms), to produce relevant high-resolution metabolite maps of grade III IDH-mutant oligodendroglioma in a single patient. This study demonstrates the potential utility of MRSI in the clinical setting at 3 Tesla.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-018-26096-y
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2018
    detail.hit.zdb_id: 2615211-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 2
    Online Resource
    Online Resource
    Density‐weighted concentric rings k ‐space trajectory for 1 H magnetic resonance spectroscopic imaging at 7 T
    Wiley ; 2018
    In:  NMR in Biomedicine Vol. 31, No. 1 ( 2018-01)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 31, No. 1 ( 2018-01)
    Abstract: It has been shown that density‐weighted (DW) k ‐space sampling with spiral and conventional phase encoding trajectories reduces spatial side lobes in magnetic resonance spectroscopic imaging (MRSI). In this study, we propose a new concentric ring trajectory (CRT) for DW‐MRSI that samples k ‐space with a density that is proportional to a spatial, isotropic Hanning window. The properties of two different DW‐CRTs were compared against a radially equidistant (RE) CRT and an echo‐planar spectroscopic imaging (EPSI) trajectory in simulations, phantoms and in vivo experiments. These experiments, conducted at 7 T with a fixed nominal voxel size and matched acquisition times, revealed that the two DW‐CRT designs improved the shape of the spatial response function by suppressing side lobes, also resulting in improved signal‐to‐noise ratio (SNR). High‐quality spectra were acquired for all trajectories from a specific region of interest in the motor cortex with an in‐plane resolution of 7.5 × 7.5 mm 2 in 8 min 3 s. Due to hardware limitations, high‐spatial‐resolution spectra with an in‐plane resolution of 5 × 5 mm 2 and an acquisition time of 12 min 48 s were acquired only for the RE and one of the DW‐CRT trajectories and not for EPSI. For all phantom and in vivo experiments, DW‐CRTs resulted in the highest SNR. The achieved in vivo spectral quality of the DW‐CRT method allowed for reliable metabolic mapping of eight metabolites including N‐acetylaspartylglutamate, γ‐aminobutyric acid and glutathione with Cramér‐Rao lower bounds below 50%, using an LCModel analysis. Finally, high‐quality metabolic mapping of a whole brain slice using DW‐CRT was achieved with a high in‐plane resolution of 5 × 5 mm 2 in a healthy subject. These findings demonstrate that our DW‐CRT MRSI technique can perform robustly on MRI systems and within a clinically feasible acquisition time.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v31.1
    DOI: 10.1002/nbm.3838
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 3
    Online Resource
    Online Resource
    Non‐water‐suppressed short‐echo‐time magnetic resonance spectroscopic imaging using a concentric ring k ‐space trajectory
    Wiley ; 2017
    In:  NMR in Biomedicine Vol. 30, No. 7 ( 2017-07)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 30, No. 7 ( 2017-07)
    Abstract: 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 mm 2 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.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v30.7
    DOI: 10.1002/nbm.3714
    Language: English
    Publisher: Wiley
    Publication Date: 2017
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 4
    Online Resource
    Online Resource
    Improved Localization for 2-Hydroxyglutarate Detection at 3 T Using Long-TE Semi-LASER
    MDPI AG ; 2016
    In:  Tomography Vol. 2, No. 2 ( 2016-06-01), p. 94-105
    Details
    In: Tomography, MDPI AG, Vol. 2, No. 2 ( 2016-06-01), p. 94-105
    Abstract: 2-hydroxyglutarate (2-HG) has emerged as a biomarker of tumor cell isocitrate dehydrogenase mutations that may enable the differential diagnosis of patients with glioma. At 3 T, detection of 2-HG with magnetic resonance spectroscopy is challenging because of metabolite signal overlap and spectral pattern modulation by slice selection and chemical shift displacement. Using density matrix simulations and phantom experiments, an optimized semi-LASER scheme (echo time = 110 milliseconds) considerably improves localization of the 2-HG spin system compared with that of an existing point-resolved spectroscopy sequence. This results in a visible 2-HG peak in the in vivo spectra at 1.9 ppm in the majority of isocitrate dehydrogenase-mutated tumors. Detected concentrations of 2-HG were similar using both sequences, although the use of semi-LASER generated narrower confidence intervals. Signal overlap with glutamate and glutamine, as measured by pairwise fitting correlation, was reduced. Lactate was readily detectable across patients with glioma using the method presented here (mean Cramér–Rao lower bound: 10% ± 2%). Together with more robust 2-HG detection, long-echo time semi-LASER offers the potential to investigate tumor metabolism and stratify patients in vivo at 3 T.
    Type of Medium: Online Resource
    ISSN: 2379-139X
    URL: Article
    URL: Article
    DOI: 10.18383/j.tom.2016.00139
    DOI: 10.18383/j.tom.2016.00139.sup.01
    Language: English
    Publisher: MDPI AG
    Publication Date: 2016
    detail.hit.zdb_id: 2857000-5
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 5
    Online Resource
    Online Resource
    Noninvasive Quantification of 2-Hydroxyglutarate in Human Gliomas with IDH1 and IDH2 Mutations
    American Association for Cancer Research (AACR) ; 2016
    In:  Cancer Research Vol. 76, No. 1 ( 2016-01-01), p. 43-49
    Details
    In: Cancer Research, American Association for Cancer Research (AACR), Vol. 76, No. 1 ( 2016-01-01), p. 43-49
    Abstract: Mutations in the isocitrate dehydrogenase genes (IDH1/2) occur often in diffuse gliomas, where they are associated with abnormal accumulation of the oncometabolite 2-hydroxyglutarate (2-HG). Monitoring 2-HG levels could provide prognostic information in this disease, but detection strategies that are noninvasive and sufficiently quantitative have yet to be developed. In this study, we address this need by presenting a proton magnetic resonance spectroscopy (1H-MRS) acquisition scheme that uses an ultrahigh magnetic field (≥7T) capable of noninvasively detecting 2-HG with quantitative measurements sufficient to differentiate mutant cytosolic IDH1 and mitochondrial IDH2 in human brain tumors. Untargeted metabolomics analysis of in vivo 1H-MRS spectra discriminated between IDH-mutant tumors and healthy tissue, and separated IDH1 from IDH2 mutations. High-quality spectra enabled the quantification of neurochemical profiles consisting of at least eight metabolites, including 2-HG, glutamate, lactate, and glutathione in both tumor and healthy tissue voxels. Notably, IDH2 mutation produced more 2-HG than IDH1 mutation, consistent with previous findings in cell culture. By offering enhanced sensitivity and specificity, this scheme can quantitatively detect 2-HG and associated metabolites that may accumulate during tumor progression, with implications to better monitor patient responses to therapy. Cancer Res; 76(1); 43–49. ©2015 AACR.
    Type of Medium: Online Resource
    ISSN: 0008-5472 , 1538-7445
    URL: Article
    DOI: 10.1158/0008-5472.CAN-15-0934
    RVK:
    XA 36000
    RVK:
    XA 10000
    Language: English
    Publisher: American Association for Cancer Research (AACR)
    Publication Date: 2016
    detail.hit.zdb_id: 2036785-5
    detail.hit.zdb_id: 1432-1
    detail.hit.zdb_id: 410466-3
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
  • 6
    Online Resource
    Online Resource
    A comparison of 2‐hydroxyglutarate detection at 3 and 7 T with long‐TE semi‐LASER
    Wiley ; 2018
    In:  NMR in Biomedicine Vol. 31, No. 3 ( 2018-03)
    Details
    In: NMR in Biomedicine, Wiley, Vol. 31, No. 3 ( 2018-03)
    Abstract: Abnormally high levels of the ‘oncometabolite’ 2‐hydroxyglutarate (2‐HG) occur in many grade II and III gliomas, and correlate with mutations in the genes of isocitrate dehydrogenase (IDH) isoforms. In vivo measurement of 2‐HG in patients, using magnetic resonance spectroscopy (MRS), has largely been carried out at 3 T, yet signal overlap continues to pose a challenge for 2‐HG detection. To combat this, several groups have proposed MRS methods at ultra‐high field ( ≥ 7 T) where theoretical increases in signal‐to‐noise ratio and spectral resolution could improve 2‐HG detection. Long echo time (long‐TE) semi‐localization by adiabatic selective refocusing (semi‐LASER) (TE = 110 ms) is a promising method for improved 2‐HG detection in vivo at either 3 or 7 T owing to the use of broad‐band adiabatic localization. Using previously published semi‐LASER methods at 3 and 7 T, this study directly compares the detectability of 2‐HG in phantoms and in vivo across nine patients. Cramér–Rao lower bounds (CRLBs) of 2‐HG fitting were found to be significantly lower at 7 T (6 ± 2%) relative to 3 T (15 ± 7%) ( p = 0.0019), yet were larger at 7 T in an IDH wild‐type patient. Although no increase in SNR was detected at 7 T (77 ± 26) relative to 3 T (77 ± 30), the detection of 2‐HG was greatly enhanced through an improved spectral profile and increased resolution at 7 T. 7 T had a large effect on pairwise fitting correlations between γ‐aminobutyric acid (GABA) and 2‐HG ( p = 0.004), and resulted in smaller coefficients. The increased sensitivity for 2‐HG detection using long‐TE acquisition at 7 T may allow for more rapid estimation of 2‐HG (within a few spectral averages) together with other associated metabolic markers in glioma.
    Type of Medium: Online Resource
    ISSN: 0952-3480 , 1099-1492
    URL: Issue
    URL: Article
    DOI: 10.1002/nbm.v31.3
    DOI: 10.1002/nbm.3886
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2002003-X
    detail.hit.zdb_id: 1000976-0
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...