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Dirk Mayer - One of the best experts on this subject based on the ideXlab platform.

  • speeding up dynamic spiral Chemical Shift Imaging with incoherent sampling and low rank matrix completion
    Magnetic Resonance in Medicine, 2017
    Co-Authors: Stephen Devience, Dirk Mayer
    Abstract:

    PURPOSE To improve the temporal and spatial resolution of dynamic 13 C spiral Chemical Shift Imaging via incoherent sampling and low-rank matrix completion (LRMC). METHODS Spiral CSI data were both simulated and acquired in rats, and undersampling was implemented retrospectively and prospectively by pseudorandomly omitting a fraction of the spiral interleaves. Undersampled data were reconstructed with both LRMC and a conventional inverse nonuniform fast Fourier transform (iNUFFT) and compared with fully sampled data. RESULTS Two-fold undersampling with LRMC reconstruction enabled a two-fold improvement in temporal or spatial resolution without significant artifacts or spatiotemporal distortion. Conversely, undersampling with iNUFFT reconstruction created strong artifacts that obscured the image. LRMC performed better at time points with strong metabolite signal. CONCLUSION Incoherent undersampling and LRMC provides a way to increase the spatiotemporal resolution of spiral CSI without degrading data integrity. Magn Reson Med 77:951-960, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

  • volumetric spiral Chemical Shift Imaging of hyperpolarized 2 13c pyruvate in a rat c6 glioma model
    Magnetic Resonance in Medicine, 2016
    Co-Authors: Jae Mo Park, Sonal Josan, Ralph E Hurd, Ronald Dean Watkins, Dirk Mayer, Taichang Jang, Milton Merchant, Lawrence Recht, Daniel M Spielman
    Abstract:

    Purpose MRS of hyperpolarized [2-13C]pyruvate can be used to assess multiple metabolic pathways within mitochondria as the 13C label is not lost with the conversion of pyruvate to acetyl-CoA. This study presents the first MR spectroscopic Imaging of hyperpolarized [2-13C]pyruvate in glioma-bearing brain. Methods Spiral Chemical Shift Imaging with spectrally undersampling scheme (1042 Hz) and a hard-pulse excitation was exploited to simultaneously image [2-13C]pyruvate, [2-13C]lactate, and [5-13C]glutamate, the metabolites known to be produced in brain after an injection of hyperpolarized [2-13C]pyruvate, without Chemical Shift displacement artifacts. A separate undersampling scheme (890 Hz) was also used to image [1-13C]acetyl-carnitine. Healthy and C6 glioma-implanted rat brains were imaged at baseline and after dichloroacetate administration, a drug that modulates pyruvate dehydrogenase kinase activity. Results The baseline metabolite maps showed higher lactate and lower glutamate in tumor as compared to normal-appearing brain. Dichloroacetate led to an increase in glutamate in both tumor and normal-appearing brain. Dichloroacetate-induced %-decrease of lactate/glutamate was comparable to the lactate/bicarbonate decrease from hyperpolarized [1-13C]pyruvate studies. Acetyl-carnitine was observed in the muscle/fat tissue surrounding the brain. Conclusion Robust volumetric Imaging with hyperpolarized [2-13C]pyruvate and downstream products was performed in glioma-bearing rat brains, demonstrating changes in mitochondrial metabolism with dichloroacetate. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

  • dynamic metabolic Imaging of hyperpolarized 2 13c pyruvate using spiral Chemical Shift Imaging with alternating spectral band excitation
    Magnetic Resonance in Medicine, 2014
    Co-Authors: Sonal Josan, Ralph E Hurd, Jae Mo Park, Yifen Yen, Ronald Dean Watkins, Adolf Pfefferbaum, Daniel M Spielman, Dirk Mayer
    Abstract:

    Purpose In contrast to [1-13C]pyruvate, hyperpolarized [2-13C]pyruvate permits the ability to follow the 13C label beyond flux through pyruvate dehydrogenase complex and investigate the incorporation of acetyl-coenzyme A into different metabolic pathways. However, Chemical Shift Imaging (CSI) with [2-13C]pyruvate is challenging owing to the large spectral dispersion of the resonances, which also leads to severe Chemical Shift displacement artifacts for slice-selective acquisitions. Methods This study introduces a sequence for three-dimensional CSI of [2-13C]pyruvate using spectrally selective excitation of limited frequency bands containing a subset of metabolites. Dynamic CSI data were acquired alternately from multiple frequency bands in phantoms for sequence testing and in vivo in rat heart. Results Phantom experiments verified the radiofrequency pulse design and demonstrated that the signal behavior of each group of resonances was unaffected by excitation of the other frequency bands. Dynamic three-dimensional 13C CSI data demonstrated the sequence capability to image pyruvate, lactate, acetylcarnitine, glutamate, and acetoacetate, enabling the analysis of organ-specific spectra and metabolite time courses. Conclusions The presented method allows CSI of widely separated resonances without Chemical Shift displacement artifact, acquiring multiple frequency bands alternately to obtain dynamic time-course information. This approach enables robust Imaging of downstream metabolic products of acetyl-coenzyme A with hyperpolarized [2-13C]pyruvate. Magn Reson Med 71:2051–2058, 2014. © 2013 Wiley Periodicals, Inc.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Dirk Mayer, Ralph E Hurd, Yifen Yen, Adolf Pfefferbaum, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized (13)C(1)-pyruvate and metabolic products (13)C(1)-lactate and (13)C(1)-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Ralph E Hurd, Adolf Pfefferbaum, Dirk Mayer, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized 13C1-pyruvate and metabolic products 13C1-lactate and 13C1-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

Daniel M Spielman - One of the best experts on this subject based on the ideXlab platform.

  • volumetric spiral Chemical Shift Imaging of hyperpolarized 2 13c pyruvate in a rat c6 glioma model
    Magnetic Resonance in Medicine, 2016
    Co-Authors: Jae Mo Park, Sonal Josan, Ralph E Hurd, Ronald Dean Watkins, Dirk Mayer, Taichang Jang, Milton Merchant, Lawrence Recht, Daniel M Spielman
    Abstract:

    Purpose MRS of hyperpolarized [2-13C]pyruvate can be used to assess multiple metabolic pathways within mitochondria as the 13C label is not lost with the conversion of pyruvate to acetyl-CoA. This study presents the first MR spectroscopic Imaging of hyperpolarized [2-13C]pyruvate in glioma-bearing brain. Methods Spiral Chemical Shift Imaging with spectrally undersampling scheme (1042 Hz) and a hard-pulse excitation was exploited to simultaneously image [2-13C]pyruvate, [2-13C]lactate, and [5-13C]glutamate, the metabolites known to be produced in brain after an injection of hyperpolarized [2-13C]pyruvate, without Chemical Shift displacement artifacts. A separate undersampling scheme (890 Hz) was also used to image [1-13C]acetyl-carnitine. Healthy and C6 glioma-implanted rat brains were imaged at baseline and after dichloroacetate administration, a drug that modulates pyruvate dehydrogenase kinase activity. Results The baseline metabolite maps showed higher lactate and lower glutamate in tumor as compared to normal-appearing brain. Dichloroacetate led to an increase in glutamate in both tumor and normal-appearing brain. Dichloroacetate-induced %-decrease of lactate/glutamate was comparable to the lactate/bicarbonate decrease from hyperpolarized [1-13C]pyruvate studies. Acetyl-carnitine was observed in the muscle/fat tissue surrounding the brain. Conclusion Robust volumetric Imaging with hyperpolarized [2-13C]pyruvate and downstream products was performed in glioma-bearing rat brains, demonstrating changes in mitochondrial metabolism with dichloroacetate. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

  • dynamic metabolic Imaging of hyperpolarized 2 13c pyruvate using spiral Chemical Shift Imaging with alternating spectral band excitation
    Magnetic Resonance in Medicine, 2014
    Co-Authors: Sonal Josan, Ralph E Hurd, Jae Mo Park, Yifen Yen, Ronald Dean Watkins, Adolf Pfefferbaum, Daniel M Spielman, Dirk Mayer
    Abstract:

    Purpose In contrast to [1-13C]pyruvate, hyperpolarized [2-13C]pyruvate permits the ability to follow the 13C label beyond flux through pyruvate dehydrogenase complex and investigate the incorporation of acetyl-coenzyme A into different metabolic pathways. However, Chemical Shift Imaging (CSI) with [2-13C]pyruvate is challenging owing to the large spectral dispersion of the resonances, which also leads to severe Chemical Shift displacement artifacts for slice-selective acquisitions. Methods This study introduces a sequence for three-dimensional CSI of [2-13C]pyruvate using spectrally selective excitation of limited frequency bands containing a subset of metabolites. Dynamic CSI data were acquired alternately from multiple frequency bands in phantoms for sequence testing and in vivo in rat heart. Results Phantom experiments verified the radiofrequency pulse design and demonstrated that the signal behavior of each group of resonances was unaffected by excitation of the other frequency bands. Dynamic three-dimensional 13C CSI data demonstrated the sequence capability to image pyruvate, lactate, acetylcarnitine, glutamate, and acetoacetate, enabling the analysis of organ-specific spectra and metabolite time courses. Conclusions The presented method allows CSI of widely separated resonances without Chemical Shift displacement artifact, acquiring multiple frequency bands alternately to obtain dynamic time-course information. This approach enables robust Imaging of downstream metabolic products of acetyl-coenzyme A with hyperpolarized [2-13C]pyruvate. Magn Reson Med 71:2051–2058, 2014. © 2013 Wiley Periodicals, Inc.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Dirk Mayer, Ralph E Hurd, Yifen Yen, Adolf Pfefferbaum, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized (13)C(1)-pyruvate and metabolic products (13)C(1)-lactate and (13)C(1)-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Ralph E Hurd, Adolf Pfefferbaum, Dirk Mayer, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized 13C1-pyruvate and metabolic products 13C1-lactate and 13C1-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

  • fast parallel spiral Chemical Shift Imaging at 3t using iterative sense reconstruction
    Magnetic Resonance in Medicine, 2008
    Co-Authors: Daniel M Spielman, Dirk Mayer, Donghyun Kim, Roland Bammer
    Abstract:

    Spiral Chemical Shift Imaging (CSI) is a fast CSI technique that simultaneously encodes 1D spectral and 2D spatial information. Therefore, it potentially allows one to perform a 2D-CSI experiment in a single shot. However, for most applications, limitations on maximum gradient strength and slew rate make multiple excitations necessary in order to achieve a desired spectral bandwidth. In this work we reduce the number of spatial interleaves and, hence, the minimum total measurement time of spiral CSI by using an iterative sensitivity encoding reconstruction algorithm which utilizes complementary spatial encoding afforded by the spatially inhomogeneous sensitivity profiles of individual receiver coils. The performance of the new method was evaluated in phantom and in vivo experiments. Parallel spiral CSI produced maps of brain metabolites similar to those obtained using conventional gridding reconstruction of the fully sampled data with only a small decrease in time-normalized signal-to-noise ratio and a small increase in noise for higher acceleration factors.

Adolf Pfefferbaum - One of the best experts on this subject based on the ideXlab platform.

  • dynamic metabolic Imaging of hyperpolarized 2 13c pyruvate using spiral Chemical Shift Imaging with alternating spectral band excitation
    Magnetic Resonance in Medicine, 2014
    Co-Authors: Sonal Josan, Ralph E Hurd, Jae Mo Park, Yifen Yen, Ronald Dean Watkins, Adolf Pfefferbaum, Daniel M Spielman, Dirk Mayer
    Abstract:

    Purpose In contrast to [1-13C]pyruvate, hyperpolarized [2-13C]pyruvate permits the ability to follow the 13C label beyond flux through pyruvate dehydrogenase complex and investigate the incorporation of acetyl-coenzyme A into different metabolic pathways. However, Chemical Shift Imaging (CSI) with [2-13C]pyruvate is challenging owing to the large spectral dispersion of the resonances, which also leads to severe Chemical Shift displacement artifacts for slice-selective acquisitions. Methods This study introduces a sequence for three-dimensional CSI of [2-13C]pyruvate using spectrally selective excitation of limited frequency bands containing a subset of metabolites. Dynamic CSI data were acquired alternately from multiple frequency bands in phantoms for sequence testing and in vivo in rat heart. Results Phantom experiments verified the radiofrequency pulse design and demonstrated that the signal behavior of each group of resonances was unaffected by excitation of the other frequency bands. Dynamic three-dimensional 13C CSI data demonstrated the sequence capability to image pyruvate, lactate, acetylcarnitine, glutamate, and acetoacetate, enabling the analysis of organ-specific spectra and metabolite time courses. Conclusions The presented method allows CSI of widely separated resonances without Chemical Shift displacement artifact, acquiring multiple frequency bands alternately to obtain dynamic time-course information. This approach enables robust Imaging of downstream metabolic products of acetyl-coenzyme A with hyperpolarized [2-13C]pyruvate. Magn Reson Med 71:2051–2058, 2014. © 2013 Wiley Periodicals, Inc.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Dirk Mayer, Ralph E Hurd, Yifen Yen, Adolf Pfefferbaum, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized (13)C(1)-pyruvate and metabolic products (13)C(1)-lactate and (13)C(1)-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Ralph E Hurd, Adolf Pfefferbaum, Dirk Mayer, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized 13C1-pyruvate and metabolic products 13C1-lactate and 13C1-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

Ralph E Hurd - One of the best experts on this subject based on the ideXlab platform.

  • volumetric spiral Chemical Shift Imaging of hyperpolarized 2 13c pyruvate in a rat c6 glioma model
    Magnetic Resonance in Medicine, 2016
    Co-Authors: Jae Mo Park, Sonal Josan, Ralph E Hurd, Ronald Dean Watkins, Dirk Mayer, Taichang Jang, Milton Merchant, Lawrence Recht, Daniel M Spielman
    Abstract:

    Purpose MRS of hyperpolarized [2-13C]pyruvate can be used to assess multiple metabolic pathways within mitochondria as the 13C label is not lost with the conversion of pyruvate to acetyl-CoA. This study presents the first MR spectroscopic Imaging of hyperpolarized [2-13C]pyruvate in glioma-bearing brain. Methods Spiral Chemical Shift Imaging with spectrally undersampling scheme (1042 Hz) and a hard-pulse excitation was exploited to simultaneously image [2-13C]pyruvate, [2-13C]lactate, and [5-13C]glutamate, the metabolites known to be produced in brain after an injection of hyperpolarized [2-13C]pyruvate, without Chemical Shift displacement artifacts. A separate undersampling scheme (890 Hz) was also used to image [1-13C]acetyl-carnitine. Healthy and C6 glioma-implanted rat brains were imaged at baseline and after dichloroacetate administration, a drug that modulates pyruvate dehydrogenase kinase activity. Results The baseline metabolite maps showed higher lactate and lower glutamate in tumor as compared to normal-appearing brain. Dichloroacetate led to an increase in glutamate in both tumor and normal-appearing brain. Dichloroacetate-induced %-decrease of lactate/glutamate was comparable to the lactate/bicarbonate decrease from hyperpolarized [1-13C]pyruvate studies. Acetyl-carnitine was observed in the muscle/fat tissue surrounding the brain. Conclusion Robust volumetric Imaging with hyperpolarized [2-13C]pyruvate and downstream products was performed in glioma-bearing rat brains, demonstrating changes in mitochondrial metabolism with dichloroacetate. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

  • dynamic metabolic Imaging of hyperpolarized 2 13c pyruvate using spiral Chemical Shift Imaging with alternating spectral band excitation
    Magnetic Resonance in Medicine, 2014
    Co-Authors: Sonal Josan, Ralph E Hurd, Jae Mo Park, Yifen Yen, Ronald Dean Watkins, Adolf Pfefferbaum, Daniel M Spielman, Dirk Mayer
    Abstract:

    Purpose In contrast to [1-13C]pyruvate, hyperpolarized [2-13C]pyruvate permits the ability to follow the 13C label beyond flux through pyruvate dehydrogenase complex and investigate the incorporation of acetyl-coenzyme A into different metabolic pathways. However, Chemical Shift Imaging (CSI) with [2-13C]pyruvate is challenging owing to the large spectral dispersion of the resonances, which also leads to severe Chemical Shift displacement artifacts for slice-selective acquisitions. Methods This study introduces a sequence for three-dimensional CSI of [2-13C]pyruvate using spectrally selective excitation of limited frequency bands containing a subset of metabolites. Dynamic CSI data were acquired alternately from multiple frequency bands in phantoms for sequence testing and in vivo in rat heart. Results Phantom experiments verified the radiofrequency pulse design and demonstrated that the signal behavior of each group of resonances was unaffected by excitation of the other frequency bands. Dynamic three-dimensional 13C CSI data demonstrated the sequence capability to image pyruvate, lactate, acetylcarnitine, glutamate, and acetoacetate, enabling the analysis of organ-specific spectra and metabolite time courses. Conclusions The presented method allows CSI of widely separated resonances without Chemical Shift displacement artifact, acquiring multiple frequency bands alternately to obtain dynamic time-course information. This approach enables robust Imaging of downstream metabolic products of acetyl-coenzyme A with hyperpolarized [2-13C]pyruvate. Magn Reson Med 71:2051–2058, 2014. © 2013 Wiley Periodicals, Inc.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Dirk Mayer, Ralph E Hurd, Yifen Yen, Adolf Pfefferbaum, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized (13)C(1)-pyruvate and metabolic products (13)C(1)-lactate and (13)C(1)-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters.

  • application of subsecond spiral Chemical Shift Imaging to real time multislice metabolic Imaging of the rat in vivo after injection of hyperpolarized 13c1 pyruvate
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Ralph E Hurd, Adolf Pfefferbaum, Dirk Mayer, James Tropp, Daniel M Spielman
    Abstract:

    Dynamic nuclear polarization can create hyperpolarized compounds with MR signal-to-noise ratio enhancements on the order of 10,000-fold. Both exogenous and normally occurring endogenous compounds can be polarized, and their initial concentration and downstream metabolic products can be assessed using MR spectroscopy. Given the transient nature of the hyperpolarized signal enhancement, fast Imaging techniques are a critical requirement for real-time metabolic Imaging. We report on the development of an ultrafast, multislice, spiral Chemical Shift Imaging sequence, with subsecond acquisition time, achieved on a clinical MR scanner. The technique was used for dynamic metabolic Imaging in rats, with measurement of time-resolved spatial distributions of hyperpolarized 13C1-pyruvate and metabolic products 13C1-lactate and 13C1-alanine, with a temporal resolution of as fast as 1 s. Metabolic Imaging revealed different signal time courses in liver from kidney. These results demonstrate the feasibility of real-time, hyperpolarized metabolic Imaging and highlight its potential in assessing organ-specific kinetic parameters. Magn Reson Med, 2009. © 2009 Wiley-Liss, Inc.

  • design of flyback echo planar readout gradients for magnetic resonance spectroscopic Imaging
    Magnetic Resonance in Medicine, 2005
    Co-Authors: Charles H Cunningham, Ralph E Hurd, Albert P Chen, Daniel B Vigneron, Sarah J Nelson, Douglas A C Kelley, John M Pauly
    Abstract:

    The spatial resolution of conventional magnetic resonance spectroscopic Imaging-(MRSI) is typically coarse, mainly due to SNR limitations. The increased signal available with higher field scanners and new array coils now permits higher spatial resolution, but conventional Chemical Shift Imaging (phase encoding) limits the spatial coverage possible in a patient-acceptable acquisition time. The "flyback" echo-planar trajectory is particularly insensitive to errors and provides data that are simple to process. In this study, high-efficiency gradient waveforms for flyback echo-planar MRSI were designed and implemented. Normal volunteer studies at 3 T showed the feasibility of acquiring high spatial resolution with large coverage in a short scan time (2048 voxels in 2.3 min and 4096 voxels in 8.5 min). The trajectories were insensitive to errors in timing and require only a modest (10 to 30%) penalty in SNR relative to conventional phase encoding using the same acquisition time.

Tamer Baysal - One of the best experts on this subject based on the ideXlab platform.

  • early and late state subacute sclerosing panencephalitis Chemical Shift Imaging and single voxel mr spectroscopy
    American Journal of Neuroradiology, 2003
    Co-Authors: Alpay Alkan, Ramazan Kutlu, Ahmet Sigirci, Kaya Sarac, Cengiz Yakinci, Mehmet Aslan, Tamer Baysal
    Abstract:

    BACKGROUND AND PURPOSE: Subacute sclerosing panencephalitis (SSPE) is a rare, progressive, inflammatory neurodegenerative disease. Our aim was to determine the metabolic abnormalities of brain in early- and late-stage SSPE by using MR spectroscopy and to assess areas of involvement in the early stages when MR Imaging findings were normal. METHODS: Children with stage II (n = 3) or III (n = 3) SSPE and 10 healthy, age-matched children underwent MR Imaging, multivoxel MR spectroscopy, and short-echo single-voxel MR spectroscopy (SVS). Areas of involvement in the brain were determined with Chemical Shift Imaging. For SVS, 2 × 2 × 2-cm voxels were placed in the frontal subcortical white matter (FSWM) and parieto-occipital white matter (POWM). N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (Ins)/Cr, and NAA/Cho ratios were calculated. RESULTS: Comparisons of NAA/Cr, Cho/Cr, Ins/Cr and NAA/Cho ratios between patients and control subjects showed significant differences in FSWM and POWM (P CONCLUSION: MR spectroscopy showed findings suggestive of inflammation in stage II and findings of demyelination, gliosis, cellular necrosis, and anaerobic metabolism in stage III. MR spectroscopy could be a promising technique for early diagnosis and treatment planning in cases of SSPE.

  • early and late state subacute sclerosing panencephalitis Chemical Shift Imaging and single voxel mr spectroscopy
    American Journal of Neuroradiology, 2003
    Co-Authors: Alpay Alkan, Ramazan Kutlu, Ahmet Sigirci, Kaya Sarac, Cengiz Yakinci, Mehmet Aslan, Tamer Baysal
    Abstract:

    BACKGROUND AND PURPOSE: Subacute sclerosing panencephalitis (SSPE) is a rare, progressive, inflammatory neurodegenerative disease. Our aim was to determine the metabolic abnormalities of brain in early- and late-stage SSPE by using MR spectroscopy and to assess areas of involvement in the early stages when MR Imaging findings were normal. METHODS: Children with stage II (n 3) or III (n 3) SSPE and 10 healthy, age-matched children underwent MR Imaging, multivoxel MR spectroscopy, and short-echo single-voxel MR spectroscopy (SVS). Areas of involvement in the brain were determined with Chemical Shift Imaging. For SVS, 2 2 2-cm voxels were placed in the frontal subcortical white matter (FSWM) and parieto-occipital white matter (POWM). N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr, myo-inositol (Ins)/Cr, and NAA/Cho ratios were calculated. RESULTS: Comparisons of NAA/Cr, Cho/Cr, Ins/Cr and NAA/Cho ratios between patients and control subjects showed significant differences in FSWM and POWM (P < .01). In patients with SSPE, NAA/Cr ratios in POWM were significantly less than those in FSWM (P < .01). NAA/Cr ratios in patients with stage II SSPE and those in the control group were not significantly different; this may reflect the absence of neuronal loss. Decreased NAA/Cr, increased Cho/Cr and Ins/Cr ratios, and increased lactate and lipid peaks were found in patients with stage III SSPE. CONCLUSION: MR spectroscopy showed findings suggestive of inflammation in stage II and findings of demyelination, gliosis, cellular necrosis, and anaerobic metabolism in stage III. MR spectroscopy could be a promising technique for early diagnosis and treatment planning in cases of SSPE.