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Michael Schar - One of the best experts on this subject based on the ideXlab platform.

  • two Repetition Time saturation transfer twist with spill over correction to measure creatine kinase reaction rates in human hearts
    Journal of Cardiovascular Magnetic Resonance, 2015
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Paul A Bottomley, Refaat E Gabr, Angela Steinberg, Robert G Weiss
    Abstract:

    Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-Repetition Time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation Time of PCr while γ-ATP is saturated, T1`, is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short Repetition Time of one of the acquisitions. Here, a two-Repetition Time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short Repetition Time is dropped. Instead of measuring T1`, an intrinsic relaxation Time T1 for PCr, T1 intrinsic, is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF). Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 intrinsic and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients. Simulations showed that both kf measured by TwiST and T1 intrinsic require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 intrinsic = 8.4 ± 1.4 s (mean ± SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33 ± 0.08 s−1 vs. 0.20 ± 0.06 s−1 in healthy vs HF hearts, respectively (p < 0.0001). TwiST was validated against TRiST in the human heart at 3 T, generating the same results 9 min faster. TwiST detected significant reductions in CK kf in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer experiments to quantify creatine kinase forward rate constants (k(f)) have previously been performed at 1.5 T. Such experiments could benefit from increased signal-to-noise ratio (SNR) and spectral resolution at 3 T. At 1.5 T, the four-angle saturation transfer method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5 T due to bandwidth limitations, power requirements, power deposition, and intrapulse spin-spin relaxation. For localized metabolite spin-lattice relaxation Time (T(1)) measurements, a dual Repetition Time approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3 T. Because the saturation transfer experiment requires a T(1) measurement performed while one reacting moiety is saturated, we adapt the dual Repetition Time approach to measure k(f) using a triple Repetition Time saturation transfer (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of k(f) are validated in human calf muscle against conventional saturation transfer and found to agree within 3%. The first 3-T TRiST measurements of creatine kinase k(f) in the human calf (n = 6), chest muscle, and heart (n = 8) are 0.26 +/- 0.04 s(-1), 0.23 +/- 0.03 s(-1), and 0.32 +/- 0.07 s(-1), respectively, consistent with prior 1.5 T values.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer (ST) experiments to quantify creatine kinase (CK) forward rate constants (kf) have previously been performed at 1.5T. Such experiments could benefit from increased signal-to-noise ratio and spectral resolution at 3T. At 1.5T, the four-angle ST method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5T due to bandwidth limitations, power requirements, power deposition and intra-pulse spin-spin decay. For localized metabolite spinlattice relaxation Time (T1) measurements, a dual Repetition Time (2TR) approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3T. Because the ST experiment requires a T1 measurement performed while one reacting moiety is saturated, we adapt the 2TR approach to measure kf using a Triple Repetition Time ST (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of kf are validated in human calf muscle against conventional ST, and found to agree within 3%. The first 3T TRiST measurements of CK kf in the human calf (n=6), chest muscle and heart (n=8) are: 0.26±0.04s −1 , 0.23±0.03s −1 and 0.32±0.07s −1 , respectively, consistent with prior 1.5T values.

Paul A Bottomley - One of the best experts on this subject based on the ideXlab platform.

  • two Repetition Time saturation transfer twist with spill over correction to measure creatine kinase reaction rates in human hearts
    Journal of Cardiovascular Magnetic Resonance, 2015
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Paul A Bottomley, Refaat E Gabr, Angela Steinberg, Robert G Weiss
    Abstract:

    Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-Repetition Time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation Time of PCr while γ-ATP is saturated, T1`, is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short Repetition Time of one of the acquisitions. Here, a two-Repetition Time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short Repetition Time is dropped. Instead of measuring T1`, an intrinsic relaxation Time T1 for PCr, T1 intrinsic, is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF). Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 intrinsic and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients. Simulations showed that both kf measured by TwiST and T1 intrinsic require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 intrinsic = 8.4 ± 1.4 s (mean ± SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33 ± 0.08 s−1 vs. 0.20 ± 0.06 s−1 in healthy vs HF hearts, respectively (p < 0.0001). TwiST was validated against TRiST in the human heart at 3 T, generating the same results 9 min faster. TwiST detected significant reductions in CK kf in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer experiments to quantify creatine kinase forward rate constants (k(f)) have previously been performed at 1.5 T. Such experiments could benefit from increased signal-to-noise ratio (SNR) and spectral resolution at 3 T. At 1.5 T, the four-angle saturation transfer method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5 T due to bandwidth limitations, power requirements, power deposition, and intrapulse spin-spin relaxation. For localized metabolite spin-lattice relaxation Time (T(1)) measurements, a dual Repetition Time approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3 T. Because the saturation transfer experiment requires a T(1) measurement performed while one reacting moiety is saturated, we adapt the dual Repetition Time approach to measure k(f) using a triple Repetition Time saturation transfer (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of k(f) are validated in human calf muscle against conventional saturation transfer and found to agree within 3%. The first 3-T TRiST measurements of creatine kinase k(f) in the human calf (n = 6), chest muscle, and heart (n = 8) are 0.26 +/- 0.04 s(-1), 0.23 +/- 0.03 s(-1), and 0.32 +/- 0.07 s(-1), respectively, consistent with prior 1.5 T values.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer (ST) experiments to quantify creatine kinase (CK) forward rate constants (kf) have previously been performed at 1.5T. Such experiments could benefit from increased signal-to-noise ratio and spectral resolution at 3T. At 1.5T, the four-angle ST method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5T due to bandwidth limitations, power requirements, power deposition and intra-pulse spin-spin decay. For localized metabolite spinlattice relaxation Time (T1) measurements, a dual Repetition Time (2TR) approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3T. Because the ST experiment requires a T1 measurement performed while one reacting moiety is saturated, we adapt the 2TR approach to measure kf using a Triple Repetition Time ST (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of kf are validated in human calf muscle against conventional ST, and found to agree within 3%. The first 3T TRiST measurements of CK kf in the human calf (n=6), chest muscle and heart (n=8) are: 0.26±0.04s −1 , 0.23±0.03s −1 and 0.32±0.07s −1 , respectively, consistent with prior 1.5T values.

Dwight G Nishimura - One of the best experts on this subject based on the ideXlab platform.

  • noncontrast enhanced renal angiography using multiple inversion recovery and alternating tr balanced steady state free precession
    Magnetic Resonance in Medicine, 2013
    Co-Authors: Hattie Zhi Chen Dong, Shreyas S Vasanawala, Pauline W Worters, Reeve R Ingle, Dwight G Nishimura
    Abstract:

    Noncontrast-enhanced renal angiography techniques based on balanced steady-state free precession avoid external contrast agents, take advantage of high inherent blood signal from the T 2 / T 1 contrast mechanism, and have short steady-state free precession acquisition Times. However, background suppression is limited; inflow Times are inflexible; labeling region is difficult to define when tagging arterial flow; and scan Times are long. To overcome these limitations, we propose the use of multiple inversion recovery preparatory pulses combined with alternating pulse Repetition Time balanced steady-state free precession to produce renal angiograms. Multiple inversion recovery uses selective spatial saturation followed by four nonselective inversion recovery pulses to concurrently null a wide range of background T 1 species while allowing for adjustable inflow Times; alternating pulse Repetition Time steady-state free precession maintains vessel contrast and provides added fat suppression. The high level of suppression enables imaging in three-dimensional as well as projective two-dimensional formats, the latter of which has a scan Time as short as one heartbeat. In vivo studies at 1.5 T demonstrate the superior vessel contrast of this technique.

  • positive contrast with alternating Repetition Time ssfp parts a fast imaging technique for spio labeled cells
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Tolga Cukur, Mayumi Yamada, William R Overall, Phillip C Yang, Dwight G Nishimura
    Abstract:

    There has been recent interest in positive-contrast MRI methods for noninvasive tracking of cells labeled with superparamagnetic iron-oxide (SPIO) nanoparticles. Low-tip-angle balanced steady-state free precession (bSSFP) sequences have been used for fast, high-resolution, and flow-insensitive positive-contrast imaging; however, the contrast can be compromised by the limited suppression of the on-resonant and fat signals. In this work, a new technique that produces positive contrast with alternating Repetition Time SSFP (PARTS) is proposed to achieve robust background suppression for a broad range of tissue parameters. In vitro and in vivo experiments demonstrate the reliability of the generated positive contrast. The results indicate that PARTS can enhance the suppression level by up to 18 dB compared with conventional bSSFP.

  • multiple Repetition Time balanced steady state free precession imaging
    Magnetic Resonance in Medicine, 2009
    Co-Authors: Tolga Cukur, Dwight G Nishimura
    Abstract:

    Although balanced steady-state free precession (bSSFP) imaging yields high signal-to-noise ratio (SNR) efficiency, the bright lipid signal is often undesirable. The bSSFP spectrum can be shaped to suppress the fat signal with scan-efficient alternating Repetition Time (ATR) bSSFP. However, the level of suppression is limited, and the pass-band is narrow due to its non-uniform shape. A multiple Repetition Time (TR) bSSFP scheme is proposed that creates a broad stop-band with a scan efficiency comparable to ATR-SSFP. Furthermore, the pass-band signal uniformity is improved, resulting in fewer shading/banding artifacts. When data acquisition occurs in more than a single TR within the multiple-TR period, the echoes can be combined to significantly improve the level of suppression. The signal characteristics of the proposed technique were compared with bSSFP and ATR-SSFP. The multiple-TR method generates identical contrast to bSSFP, while achieving up to an order of magnitude higher stop-band suppression than ATR-SSFP. In vivo studies at 1.5 T and 3 T demonstrate the superior fat suppression performance of multiple-TR bSSFP.

  • fat water separation with alternating Repetition Time balanced ssfp
    Magnetic Resonance in Medicine, 2008
    Co-Authors: Tolga Cukur, Dwight G Nishimura
    Abstract:

    Balanced SSFP achieves high SNR efficiency, but suffers from bright fat signal. In this work, a multiple-acquisition fat-water separation technique using alternating Repetition Time (ATR) balanced SSFP is proposed. The SSFP profile can be modified using alternating Repetition Times and appropriate phase cycling to yield two spectra where fat and water are in-phase and out-of-phase respectively. The signal homogeneity and the broad width of the created in-phase and out-of-phase profiles lead to signal cancellation over a broad stop-band. The stop-band suppression is achieved for a wide range of flip angles and tissue parameters. This property, coupled with the inherent flexibility of ATR SSFP in Repetition Time selection, makes the method a good candidate for fat-suppressed SSFP imaging. The proposed method can be tailored to achieve a smaller residual stop-band signal or a decreased sensitivity to field inhomogeneity depending on application-specific needs.

  • fat suppressed steady state free precession imaging using phase detection
    Magnetic Resonance in Medicine, 2003
    Co-Authors: Brian A Hargreaves, Shreyas S Vasanawala, Krishna S Nayak, Dwight G Nishimura
    Abstract:

    Fully refocused steady-state free precession (SSFP) is a rapid, efficient imaging sequence that can provide diagnostically useful image contrast. In SSFP, the signal is refocused midway between excitation pulses, much like in a spin-echo experiment. However, in SSFP, the phase of the refocused spins alternates for each resonant frequency interval equal to the reciprocal of the sequence Repetition Time (TR). Appropriate selection of the TR results in a 180° phase difference between lipid and water signals. This phase difference can be used for fat‐water separation in SSFP without any increase in scan Time. The technique is shown to produce excellent non-contrast-enhanced, flow-independent angiograms of the peripheral vasculature. Magn Reson Med 50: 210‐213, 2003. © 2003 Wiley-Liss, Inc.

Robert G Weiss - One of the best experts on this subject based on the ideXlab platform.

  • two Repetition Time saturation transfer twist with spill over correction to measure creatine kinase reaction rates in human hearts
    Journal of Cardiovascular Magnetic Resonance, 2015
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Paul A Bottomley, Refaat E Gabr, Angela Steinberg, Robert G Weiss
    Abstract:

    Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-Repetition Time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation Time of PCr while γ-ATP is saturated, T1`, is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short Repetition Time of one of the acquisitions. Here, a two-Repetition Time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short Repetition Time is dropped. Instead of measuring T1`, an intrinsic relaxation Time T1 for PCr, T1 intrinsic, is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF). Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 intrinsic and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients. Simulations showed that both kf measured by TwiST and T1 intrinsic require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 intrinsic = 8.4 ± 1.4 s (mean ± SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33 ± 0.08 s−1 vs. 0.20 ± 0.06 s−1 in healthy vs HF hearts, respectively (p < 0.0001). TwiST was validated against TRiST in the human heart at 3 T, generating the same results 9 min faster. TwiST detected significant reductions in CK kf in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer experiments to quantify creatine kinase forward rate constants (k(f)) have previously been performed at 1.5 T. Such experiments could benefit from increased signal-to-noise ratio (SNR) and spectral resolution at 3 T. At 1.5 T, the four-angle saturation transfer method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5 T due to bandwidth limitations, power requirements, power deposition, and intrapulse spin-spin relaxation. For localized metabolite spin-lattice relaxation Time (T(1)) measurements, a dual Repetition Time approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3 T. Because the saturation transfer experiment requires a T(1) measurement performed while one reacting moiety is saturated, we adapt the dual Repetition Time approach to measure k(f) using a triple Repetition Time saturation transfer (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of k(f) are validated in human calf muscle against conventional saturation transfer and found to agree within 3%. The first 3-T TRiST measurements of creatine kinase k(f) in the human calf (n = 6), chest muscle, and heart (n = 8) are 0.26 +/- 0.04 s(-1), 0.23 +/- 0.03 s(-1), and 0.32 +/- 0.07 s(-1), respectively, consistent with prior 1.5 T values.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer (ST) experiments to quantify creatine kinase (CK) forward rate constants (kf) have previously been performed at 1.5T. Such experiments could benefit from increased signal-to-noise ratio and spectral resolution at 3T. At 1.5T, the four-angle ST method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5T due to bandwidth limitations, power requirements, power deposition and intra-pulse spin-spin decay. For localized metabolite spinlattice relaxation Time (T1) measurements, a dual Repetition Time (2TR) approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3T. Because the ST experiment requires a T1 measurement performed while one reacting moiety is saturated, we adapt the 2TR approach to measure kf using a Triple Repetition Time ST (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of kf are validated in human calf muscle against conventional ST, and found to agree within 3%. The first 3T TRiST measurements of CK kf in the human calf (n=6), chest muscle and heart (n=8) are: 0.26±0.04s −1 , 0.23±0.03s −1 and 0.32±0.07s −1 , respectively, consistent with prior 1.5T values.

Abdel Monem M Elsharkawy - One of the best experts on this subject based on the ideXlab platform.

  • two Repetition Time saturation transfer twist with spill over correction to measure creatine kinase reaction rates in human hearts
    Journal of Cardiovascular Magnetic Resonance, 2015
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Paul A Bottomley, Refaat E Gabr, Angela Steinberg, Robert G Weiss
    Abstract:

    Phosphorus saturation transfer (ST) magnetic resonance spectroscopy can measure the rate of ATP generated from phosphocreatine (PCr) via creatine kinase (CK) in the human heart. Recently, the triple-Repetition Time ST (TRiST) method was introduced to measure the CK pseudo-first-order rate constant kf in three acquisitions. In TRiST, the longitudinal relaxation Time of PCr while γ-ATP is saturated, T1`, is measured for each subject, but suffers from low SNR because the PCr signal is reduced due to exchange with saturated γ-ATP, and the short Repetition Time of one of the acquisitions. Here, a two-Repetition Time ST (TwiST) method is presented. In TwiST, the acquisition with γ-ATP saturation and short Repetition Time is dropped. Instead of measuring T1`, an intrinsic relaxation Time T1 for PCr, T1 intrinsic, is assumed. The objective was to validate TwiST measurements of CK kinetics in healthy subjects and patients with heart failure (HF). Bloch equation simulations that included the effect of spillover irradiation on PCr were used to derive formulae for T1 intrinsic and kf measured by both TRiST and TwiST methods. Spillover was quantified from an unsaturated PCr measurement used in the current protocol for determining PCr and ATP concentrations. Cardiac TRiST and TwiST data were acquired at 3 T from 12 healthy and 17 HF patients. Simulations showed that both kf measured by TwiST and T1 intrinsic require spill-over corrections. In human heart at 3 T, the spill-over corrected T1 intrinsic = 8.4 ± 1.4 s (mean ± SD) independent of study group. TwiST and TRiST kf measurements were the same, but TwiST was 9 min faster. Spill-over corrected TwiST kf was 0.33 ± 0.08 s−1 vs. 0.20 ± 0.06 s−1 in healthy vs HF hearts, respectively (p < 0.0001). TwiST was validated against TRiST in the human heart at 3 T, generating the same results 9 min faster. TwiST detected significant reductions in CK kf in HF compared to healthy subjects, consistent with prior 1.5 T studies using different methodology.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer experiments to quantify creatine kinase forward rate constants (k(f)) have previously been performed at 1.5 T. Such experiments could benefit from increased signal-to-noise ratio (SNR) and spectral resolution at 3 T. At 1.5 T, the four-angle saturation transfer method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5 T due to bandwidth limitations, power requirements, power deposition, and intrapulse spin-spin relaxation. For localized metabolite spin-lattice relaxation Time (T(1)) measurements, a dual Repetition Time approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3 T. Because the saturation transfer experiment requires a T(1) measurement performed while one reacting moiety is saturated, we adapt the dual Repetition Time approach to measure k(f) using a triple Repetition Time saturation transfer (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of k(f) are validated in human calf muscle against conventional saturation transfer and found to agree within 3%. The first 3-T TRiST measurements of creatine kinase k(f) in the human calf (n = 6), chest muscle, and heart (n = 8) are 0.26 +/- 0.04 s(-1), 0.23 +/- 0.03 s(-1), and 0.32 +/- 0.07 s(-1), respectively, consistent with prior 1.5 T values.

  • triple Repetition Time saturation transfer trist 31p spectroscopy for measuring human creatine kinase reaction kinetics
    Magnetic Resonance in Medicine, 2010
    Co-Authors: Michael Schar, Abdel Monem M Elsharkawy, Robert G Weiss, Paul A Bottomley
    Abstract:

    Human cardiac phosphorus MR saturation transfer (ST) experiments to quantify creatine kinase (CK) forward rate constants (kf) have previously been performed at 1.5T. Such experiments could benefit from increased signal-to-noise ratio and spectral resolution at 3T. At 1.5T, the four-angle ST method was applied with low-angle adiabatic pulses and surface coils. However, low-angle adiabatic pulses are potentially problematic above 1.5T due to bandwidth limitations, power requirements, power deposition and intra-pulse spin-spin decay. For localized metabolite spinlattice relaxation Time (T1) measurements, a dual Repetition Time (2TR) approach with adiabatic half-passage pulses was recently introduced to solve these problems at 3T. Because the ST experiment requires a T1 measurement performed while one reacting moiety is saturated, we adapt the 2TR approach to measure kf using a Triple Repetition Time ST (TRiST) method. A new pulsed saturation scheme with reduced sensitivity to static magnetic field inhomogeneity and compatibility with cardiac triggering is also presented. TRiST measurements of kf are validated in human calf muscle against conventional ST, and found to agree within 3%. The first 3T TRiST measurements of CK kf in the human calf (n=6), chest muscle and heart (n=8) are: 0.26±0.04s −1 , 0.23±0.03s −1 and 0.32±0.07s −1 , respectively, consistent with prior 1.5T values.