The Experts below are selected from a list of 133086 Experts worldwide ranked by ideXlab platform
Rolf Gruetter - One of the best experts on this subject based on the ideXlab platform.
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mr spectroscopy of the human brain with Enhanced Signal intensity at ultrashort echo times on a clinical platform at 3t and 7t
Magnetic Resonance in Medicine, 2009Co-Authors: Ralf Mekle, Vladimir Mlynarik, Giulio Gambarota, Martin Hergt, Gunnar Krueger, Rolf GruetterAbstract:Recently, the spin-echo full-intensity acquired localized (SPECIAL) spectroscopy technique was proposed to unite the advantages of short TEs on the order of milliseconds (ms) with full sensitivity and applied to in vivo rat brain. In the present study, SPECIAL was adapted and optimized for use on a clinical platform at 3T and 7T by combining interleaved water suppression (WS) and outer volume saturation (OVS), optimized sequence timing, and improved shimming using FASTMAP. High-quality single voxel spectra of human brain were acquired at TEs below or equal to 6 ms on a clinical 3T and 7T system for six volunteers. Narrow linewidths (6.6 +/- 0.6 Hz at 3T and 12.1 +/- 1.0 Hz at 7T for water) and the high Signal-to-noise ratio (SNR) of the artifact-free spectra enabled the quantification of a neurochemical profile consisting of 18 metabolites with Cramer-Rao lower bounds (CRLBs) below 20% at both field strengths. The Enhanced sensitivity and increased spectral resolution at 7T compared to 3T allowed a two-fold reduction in scan time, an increased precision of quantification for 12 metabolites, and the additional quantification of lactate with CRLB below 20%. Improved sensitivity at 7T was also demonstrated by a 1.7-fold increase in average SNR (= peak height/root mean square [RMS]-of-noise) per unit-time. Magn Reson Med 61:1279-1285, 2009. (C) 2009 Wiley-Liss, Inc.
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mr spectroscopy of the human brain with Enhanced Signal intensity at ultrashort echo times on a clinical platform at 3t and 7t
Magnetic Resonance in Medicine, 2009Co-Authors: Ralf Mekle, Vladimir Mlynarik, Giulio Gambarota, Martin Hergt, Gunnar Krueger, Rolf GruetterAbstract:Recently, the spin-echo full-intensity acquired localized (SPECIAL) spectroscopy technique was proposed to unite the advantages of short TEs on the order of milliseconds (ms) with full sensitivity and applied to in vivo rat brain. In the present study, SPECIAL was adapted and optimized for use on a clinical platform at 3T and 7T by combining interleaved water suppression (WS) and outer volume saturation (OVS), optimized sequence timing, and improved shimming using FASTMAP. High-quality single voxel spectra of human brain were acquired at TEs below or equal to 6 ms on a clinical 3T and 7T system for six volunteers. Narrow linewidths (6.6 +/- 0.6 Hz at 3T and 12.1 +/- 1.0 Hz at 7T for water) and the high Signal-to-noise ratio (SNR) of the artifact-free spectra enabled the quantification of a neurochemical profile consisting of 18 metabolites with Cramer-Rao lower bounds (CRLBs) below 20% at both field strengths. The Enhanced sensitivity and increased spectral resolution at 7T compared to 3T allowed a two-fold reduction in scan time, an increased precision of quantification for 12 metabolites, and the additional quantification of lactate with CRLB below 20%. Improved sensitivity at 7T was also demonstrated by a 1.7-fold increase in average SNR (= peak height/root mean square [RMS]-of-noise) per unit-time.
Luc Thevenaz - One of the best experts on this subject based on the ideXlab platform.
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high spatial and spectral resolution long range sensing using brillouin echoes
Journal of Lightwave Technology, 2010Co-Authors: Stella M Foaleng, Moshe Tur, Jeancharles Beugnot, Luc ThevenazAbstract:High spatial ( cm) and spectral ( MHz) resolution Brillouin sensing is realized with Enhanced Signal to noise ratio using a pre-activated acoustic field and an optical phase control over the interrogating pulse. Pre-activation of the acoustic field preserves the Brillouin natural linewidth and a differential gain technique extends the method to long ranges. Experimentally, fully resolved measurements of the Brillouin frequency shift of a 5 cm spot perturbation at the far end of a 5 km fiber have been performed with a frequency resolution of 3 MHz (2) , using a 500 ps (5 cm) phase shift pulse.
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high spatial and spectral resolution long range sensing using brillouin echoes
Journal of Lightwave Technology, 2010Co-Authors: Stella M Foaleng, Jeancharles Beugnot, Luc ThevenazAbstract:High spatial ( cm) and spectral ( MHz) resolution Brillouin sensing is realized with Enhanced Signal to noise ratio using a pre-activated acoustic field and an optical phase control over the interrogating pulse. Pre-activation of the acoustic field preserves the Brillouin natural linewidth and a differential gain technique extends the method to long ranges. Experimentally, fully resolved measurements of the Brillouin frequency shift of a 5 cm spot perturbation at the far end of a 5 km fiber have been performed with a frequency resolution of 3 MHz (2) , using a 500 ps (5 cm) phase shift pulse.
Jeffrey H Maki - One of the best experts on this subject based on the ideXlab platform.
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evaluation of four injection profiles for uniform contrast Enhanced Signal intensity profiles in mr angiography
Journal of Magnetic Resonance Imaging, 2019Co-Authors: Jeffrey H Maki, Gregory J Wilson, Toshimasa J ClarkAbstract:BACKGROUND Gadolinium concentration variation during acquisition of contrast-Enhanced MR angiography (CE-MRA) may lead to artifacts. PURPOSE To compare Signal intensity (SI) profiles of four different contrast agent injection strategies during CE-MRA with the goal of minimizing SI variation during acquisition. STUDY TYPE Prospective. SUBJECTS Forty subjects randomized to receive one of four injection profiles of gadobenate dimeglumine (0.1 mmol/kg), either undiluted (0.5 M) or diluted to 40 ml total volume. Tested profiles: 1) nondiluted single-phase ("standard" NS; 1.6 ml/s), 2) diluted single-phase (DS; 1.6 ml/s), 3) diluted biphasic (DB; 9 ml @ 3.3 ml/s, 29 ml @ 1.4 ml/s), 4) patient-tailored protocol using linear prediction (DT). FIELD STRENGTH/SEQUENCE Time-resolved SI measured at 3T with spoiled gradient echo sequences having analogous parameters to those of CE-MRA. ASSESSMENT Plateau arrival time, rise time, duration, peak and tail SI, plateau quality (sum of squared residuals; SSR), average SI for each injection type derived were used. STATISTICAL TEST Two-tailed t-test. RESULTS Peak SI, arrival, and rise times were not significantly different between groups, excepting peak SI DB slightly > DS (P = 0.042). Duration of NS vs. the diluted groups was significantly shorter (all P < 0.0001), and DS duration was significantly shorter than that of DT and DB (NS 11.4 ± 3.5 vs. DS 22.9 ± 4.3, DB 25.4 ± 2.3, DT 28.3 ± 4.1 sec). Quality (SSR) of the 20-second plateau was significantly better for DS, DB, DT as compared with NS (all P < 0.001). DATA CONCLUSION Three different strategies to power-inject diluted gadobenate dimeglumine targeting a 20-second plateau produced SI profiles with longer duration, more consistent plateau, and no significant loss in peak SI. Such injection profiles may provide more uniform SI during CE-MRA, potentially reducing blurring artifacts. LEVEL OF EVIDENCE 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1808-1816.
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evaluation of a tailored injection profile tip algorithm for uniform contrast Enhanced Signal intensity profiles in mr angiography
Journal of Magnetic Resonance Imaging, 2016Co-Authors: Gregory J Wilson, Jeffrey H MakiAbstract:PURPOSE To evaluate a contrast agent injection method that provides constant magnetic resonance imaging (MRI) Signal intensity throughout a contrast-Enhanced MR angiography acquisition. MATERIALS AND METHODS A tailored injection profile (TIP) algorithm was developed that used the Signal intensity profile from a test bolus as an impulse response function, and predicted the response to various multiphasic injection profiles. Antecubital vein injections were administered via a commercially available multiphasic power injector. The TIP algorithm evaluated the predicted responses and selected the injection that best matched the desired (20-sec plateau) profile. Resulting Signal intensity profiles from tailored and standard injection profiles were compared in 20 subjects (10 each). All subjects received a weight-based single-dose (0.1 mmol/kg) of gadoteridol, and abdominal aorta Signal intensities were measured at 3T with a time-resolved, thick-slice, 3D spoiled-gradient-echo MR sequence with parameters approximating contrast-Enhanced MR angiography. The single-phase, standard injection was injected at 1.6 mL/sec. RESULTS Full-width at 80% maximum (FW80M) Signal intensity was significantly longer for the tailored injection profiles (23.0 ± 2.2 vs. 9.0 ± 4.2 sec; P < 0.01). Concurrently, the profile peak Signal intensity was reduced by 19% for the tailored profiles (12.0 ± 3.1 vs. 14.8 ± 2.8 times baseline; P = 0.058), nearly reaching significance. CONCLUSION Multiphasic tailored injections from a power injector produced longer Signal intensity profiles (156% increase in FW80M) with an accompanying decrease (19%) in peak Signal intensity compared to a standard, single-phase injection. J. Magn. Reson. Imaging 2016. J. Magn. Reson. Imaging 2016;44:1664-1672.
Ralf Mekle - One of the best experts on this subject based on the ideXlab platform.
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mr spectroscopy of the human brain with Enhanced Signal intensity at ultrashort echo times on a clinical platform at 3t and 7t
Magnetic Resonance in Medicine, 2009Co-Authors: Ralf Mekle, Vladimir Mlynarik, Giulio Gambarota, Martin Hergt, Gunnar Krueger, Rolf GruetterAbstract:Recently, the spin-echo full-intensity acquired localized (SPECIAL) spectroscopy technique was proposed to unite the advantages of short TEs on the order of milliseconds (ms) with full sensitivity and applied to in vivo rat brain. In the present study, SPECIAL was adapted and optimized for use on a clinical platform at 3T and 7T by combining interleaved water suppression (WS) and outer volume saturation (OVS), optimized sequence timing, and improved shimming using FASTMAP. High-quality single voxel spectra of human brain were acquired at TEs below or equal to 6 ms on a clinical 3T and 7T system for six volunteers. Narrow linewidths (6.6 +/- 0.6 Hz at 3T and 12.1 +/- 1.0 Hz at 7T for water) and the high Signal-to-noise ratio (SNR) of the artifact-free spectra enabled the quantification of a neurochemical profile consisting of 18 metabolites with Cramer-Rao lower bounds (CRLBs) below 20% at both field strengths. The Enhanced sensitivity and increased spectral resolution at 7T compared to 3T allowed a two-fold reduction in scan time, an increased precision of quantification for 12 metabolites, and the additional quantification of lactate with CRLB below 20%. Improved sensitivity at 7T was also demonstrated by a 1.7-fold increase in average SNR (= peak height/root mean square [RMS]-of-noise) per unit-time. Magn Reson Med 61:1279-1285, 2009. (C) 2009 Wiley-Liss, Inc.
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mr spectroscopy of the human brain with Enhanced Signal intensity at ultrashort echo times on a clinical platform at 3t and 7t
Magnetic Resonance in Medicine, 2009Co-Authors: Ralf Mekle, Vladimir Mlynarik, Giulio Gambarota, Martin Hergt, Gunnar Krueger, Rolf GruetterAbstract:Recently, the spin-echo full-intensity acquired localized (SPECIAL) spectroscopy technique was proposed to unite the advantages of short TEs on the order of milliseconds (ms) with full sensitivity and applied to in vivo rat brain. In the present study, SPECIAL was adapted and optimized for use on a clinical platform at 3T and 7T by combining interleaved water suppression (WS) and outer volume saturation (OVS), optimized sequence timing, and improved shimming using FASTMAP. High-quality single voxel spectra of human brain were acquired at TEs below or equal to 6 ms on a clinical 3T and 7T system for six volunteers. Narrow linewidths (6.6 +/- 0.6 Hz at 3T and 12.1 +/- 1.0 Hz at 7T for water) and the high Signal-to-noise ratio (SNR) of the artifact-free spectra enabled the quantification of a neurochemical profile consisting of 18 metabolites with Cramer-Rao lower bounds (CRLBs) below 20% at both field strengths. The Enhanced sensitivity and increased spectral resolution at 7T compared to 3T allowed a two-fold reduction in scan time, an increased precision of quantification for 12 metabolites, and the additional quantification of lactate with CRLB below 20%. Improved sensitivity at 7T was also demonstrated by a 1.7-fold increase in average SNR (= peak height/root mean square [RMS]-of-noise) per unit-time.
Stella M Foaleng - One of the best experts on this subject based on the ideXlab platform.
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high spatial and spectral resolution long range sensing using brillouin echoes
Journal of Lightwave Technology, 2010Co-Authors: Stella M Foaleng, Moshe Tur, Jeancharles Beugnot, Luc ThevenazAbstract:High spatial ( cm) and spectral ( MHz) resolution Brillouin sensing is realized with Enhanced Signal to noise ratio using a pre-activated acoustic field and an optical phase control over the interrogating pulse. Pre-activation of the acoustic field preserves the Brillouin natural linewidth and a differential gain technique extends the method to long ranges. Experimentally, fully resolved measurements of the Brillouin frequency shift of a 5 cm spot perturbation at the far end of a 5 km fiber have been performed with a frequency resolution of 3 MHz (2) , using a 500 ps (5 cm) phase shift pulse.
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high spatial and spectral resolution long range sensing using brillouin echoes
Journal of Lightwave Technology, 2010Co-Authors: Stella M Foaleng, Jeancharles Beugnot, Luc ThevenazAbstract:High spatial ( cm) and spectral ( MHz) resolution Brillouin sensing is realized with Enhanced Signal to noise ratio using a pre-activated acoustic field and an optical phase control over the interrogating pulse. Pre-activation of the acoustic field preserves the Brillouin natural linewidth and a differential gain technique extends the method to long ranges. Experimentally, fully resolved measurements of the Brillouin frequency shift of a 5 cm spot perturbation at the far end of a 5 km fiber have been performed with a frequency resolution of 3 MHz (2) , using a 500 ps (5 cm) phase shift pulse.