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Todd R Constable - One of the best experts on this subject based on the ideXlab platform.
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dynamic Flip Angle ecg gating with nuisance signal regression improves resting state bold functional connectivity mapping by reducing cardiogenic noise
Magnetic Resonance in Medicine, 2019Co-Authors: Chenxi Hu, Fuyuze Tokoglu, Dustin Scheinost, Xilin Shen, Dana C Peters, Gigi Galiana, Todd R ConstableAbstract:Purpose To investigate an ECG-gated dynamic-Flip-Angle BOLD sequence with improved robustness against cardiogenic noise in resting-state fMRI. Methods ECG-gating minimizes the cardiogenic noise but introduces T1 -dependent signal variation, which is minimized by combination of a dynamic-Flip-Angle technique and retrospective nuisance signal regression (NSR) using signals of white matter, CSF, and global average. The technique was studied with simulations in a wide range of T1 and B1 fields and phantom imaging with pre-programmed TR variations. Resting-state fMRI of 20 healthy subjects was acquired with non-gated BOLD (NG), ECG-gated constant-Flip-Angle BOLD (GCFA), ECG-gated BOLD with retrospective T1 -correction (GRC), and ECG-gated dynamic-Flip-Angle BOLD (GDFA), all processed by the same NSR method. GDFA was compared to alternative methods over temporal SNR (tSNR), seed-based connectivity, and whole-brain voxelwise connectivity based on intrinsic connectivity distribution (ICD). A previous large-cohort data set (N = 100) was used as a connectivity gold standard. Results Simulations and phantom imaging show substantial reduction of the T1 -dependent signal variation with GDFA alone, and further reduction with NSR. The resting-state study shows improved tSNR in the basal brain, comparing GDFA to NG, after both processed with NSR. Furthermore, GDFA significantly improved subcortical-subcortical and cortical-subcortical connectivity for several representative seeds and significantly improved ICD in the brainstem, thalamus, striatum, and prefrontal cortex, compared to the other 3 approaches. Conclusion GDFA with NSR improves mapping of the resting-state functional connectivity of the basal-brain regions by reducing cardiogenic noise.
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dynamic Flip Angle ecg gating with nuisance signal regression improves resting state bold functional connectivity mapping by reducing cardiogenic noise
Magnetic Resonance in Medicine, 2019Co-Authors: Fuyuze Tokoglu, Maolin Qiu, Dustin Scheinost, Xilin Shen, Dana C Peters, Gigi Galiana, Todd R ConstableAbstract:Purpose To investigate an ECG-gated dynamic-Flip-Angle BOLD sequence with improved robustness against cardiogenic noise in resting-state fMRI. Methods ECG-gating minimizes the cardiogenic noise but introduces T1 -dependent signal variation, which is minimized by combination of a dynamic-Flip-Angle technique and retrospective nuisance signal regression (NSR) using signals of white matter, CSF, and global average. The technique was studied with simulations in a wide range of T1 and B1 fields and phantom imaging with pre-programmed TR variations. Resting-state fMRI of 20 healthy subjects was acquired with non-gated BOLD (NG), ECG-gated constant-Flip-Angle BOLD (GCFA), ECG-gated BOLD with retrospective T1 -correction (GRC), and ECG-gated dynamic-Flip-Angle BOLD (GDFA), all processed by the same NSR method. GDFA was compared to alternative methods over temporal SNR (tSNR), seed-based connectivity, and whole-brain voxelwise connectivity based on intrinsic connectivity distribution (ICD). A previous large-cohort data set (N = 100) was used as a connectivity gold standard. Results Simulations and phantom imaging show substantial reduction of the T1 -dependent signal variation with GDFA alone, and further reduction with NSR. The resting-state study shows improved tSNR in the basal brain, comparing GDFA to NG, after both processed with NSR. Furthermore, GDFA significantly improved subcortical-subcortical and cortical-subcortical connectivity for several representative seeds and significantly improved ICD in the brainstem, thalamus, striatum, and prefrontal cortex, compared to the other 3 approaches. Conclusion GDFA with NSR improves mapping of the resting-state functional connectivity of the basal-brain regions by reducing cardiogenic noise.
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t1 measurements incorporating Flip Angle calibration and correction in vivo
Journal of Magnetic Resonance, 2006Co-Authors: Jinghua Wang, Maolin Qiu, Hyeonjin Kim, Todd R ConstableAbstract:Abstract In this work, we propose a variable FA method that combines in vivo Flip Angle (FA) calibration and correction with a short TR variable FA approach for a fast and accurate T1 mapping. The precision T1s measured across a uniform milk phantom is estimated to be 2.65% using the conventional (slow) inversion recovery (IR) method and 28.5% for the variable FA method without FA correction, and 2.2% when FA correction is included. These results demonstrate that the sensitivity of the variable FA method to RF nonuniformities can be dramatically reduced when these nonuniformities are directly measured and corrected. The acquisition time for this approach decreases to 10 min from 85 min for the conventional IR method. In addition, we report that the averaged T1s measured from five normal subjects are 900 ± 3 ms, 1337 ± 8 ms and 2180 ± 25 ms in white matter (WM), gray matter (GM) and cerebral spinal fluid (CSF) using the variable Flip Angle method with FA correction at 3 T, respectively. These results are consistent with previously reported values obtained with much longer acquisition times. The method reduces the total scan time for whole brain T1 mapping, including FA measurement and calibration, to approximately 6 min. The novelty of this method lies in the in vivo calibration and the correction of the FAs, thereby allowing a rapid and accurate T1 mapping at high field for many applications.
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factors influencing Flip Angle mapping in mri rf pulse shape slice select gradients off resonance excitation and b0 inhomogeneities
Magnetic Resonance in Medicine, 2006Co-Authors: Jinghua Wang, Weihua Mao, Maolin Qiu, Michael B Smith, Todd R ConstableAbstract:To understand the various effects that influence actual Flip Angles, and correct for these effects, it is important to precisely quantify the MRI parameters (such as T1, T2, and perfusion). In this paper actual Flip Angle maps are calculated using a conventional gradient-echo (GRE) sequence with different radiofrequency (RF) pulse shapes (Gaussian, sinc, and truncated-sinc), slice-selection gradients, off-resonance excitations, and B0 field inhomogeneities. The experimental results demonstrate that RF pulse shapes significantly affect the Flip Angle distribution and calibration factors. Off-resonance RF excitations, B0 nonuniformities, and slice-selection gradients can lead to degradations in the signal intensities of the images used to map the Flip Angle, and potentially introduce a bias and increased variance in the measured Flip Angles.
Scott B Reeder - One of the best experts on this subject based on the ideXlab platform.
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motion robust high snr liver fat quantification using a 2d sequential acquisition with a variable Flip Angle approach
Magnetic Resonance in Medicine, 2020Co-Authors: Ruiyang Zhao, Yuxin Zhang, Xiaoke Wang, Timothy J Colgan, Jennifer L Rehm, Scott B Reeder, Kevin M Johnson, Diego HernandoAbstract:Purpose Chemical shift encoded (CSE)-MRI enables quantification of proton-density fat fraction (PDFF) as a biomarker of liver fat content. However, conventional 3D Cartesian CSE-MRI methods require breath-holding. A motion-robust 2D Cartesian sequential method addresses this limitation but suffers from low SNR. In this work, a novel free breathing 2D Cartesian sequential CSE-MRI method using a variable Flip Angle approach with centric phase encoding (VFA-centric) is developed to achieve fat quantification with low T 1 bias, high SNR, and minimal blurring. Methods Numerical simulation was performed for variable Flip Angle schedule design and preliminary evaluation of VFA-centric method, along with several alternative Flip Angle designs. Phantom, adults (n = 8), and children (n = 27) were imaged at 3T. Multi-echo images were acquired and PDFF maps were estimated. PDFF standard deviation was used as a surrogate for SNR. Results In both simulation and phantom experiments, the VFA-centric method enabled higher SNR imaging with minimal T 1 bias and blurring artifacts. High correlation (slope = 1.00, intercept = 0.04, R 2 = 0.998) was observed in vivo between the proposed VFA-centric method obtained PDFF and reference PDFF (free breathing low-Flip Angle 2D sequential acquisition). Further, the proposed VFA-centric method (PDFF standard deviation = 1.5%) had a better SNR performance than the reference acquisition (PDFF standard deviation = 3.3%) with P Conclusions The proposed free breathing 2D Cartesian sequential CSE-MRI method with variable Flip Angle approach and centric-ordered phase encoding achieved motion robustness, low T 1 bias, high SNR compared to previous 2D sequential methods, and low blurring in liver fat quantification.
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t1 bias in chemical shift encoded liver fat fraction role of the Flip Angle
Journal of Magnetic Resonance Imaging, 2014Co-Authors: Jenspeter Kuhn, Diego Hernando, Christina Jahn, Werner Siegmund, Stefan Hadlich, Julia Mayerle, Jorg P Pfannmoller, Sonke Langner, Scott B ReederAbstract:MRI is a promising tool for the assessment of fat in tissue (1,2). MR-based techniques for routine clinical detection and quantification of tissue fat are well established for the liver and are of great interest in other organs and tissue such as the pancreas, bone marrow, and muscle (3–6). One simple approach for tissue fat detection is the technique of in-phase/out-of-phase chemical shift imaging (7,8). The chemical shift technique is based on differences in the resonance frequencies of protons of water and triglycerides. Recent studies have shown the chemical shift in-phase/out-of-phase approach to be suitable for clinical liver fat detection and a promising candidate for liver fat quantification (9,10). However, in-phase/out-of-phase imaging is limited by the effects of confounding factors (11), such as T2* bias, T1 bias, and the multi-peak spectral complexity of fat (12–15). Several recent techniques have been developed that acquire multiple gradient echo images acquired at increasing echo times and perform fat quantification by correcting for all relevant confounders. If all confounders are considered, the calculated fat-fraction (FF) becomes the proton-density-fat fraction (PDFF) (16). Confounder-corrected mapping of PDFF allows reliable quantification of tissue fat, with robustness to varying scan parameters (14,15) and reproducibility across MR scanners (17). Emerging quantitative techniques include confounder-corrected magnitude chemical shift-encoded MRI, restricted to FF below 50%, and confounder-corrected complex chemical shift-encoded MRI, for quantifying FF from 0–100% (1,18). T1 bias is a strong confounder for MR-based fat quantification. Fat and water have different T1 relaxation times, and this difference introduces errors in tissue fat quantification if the underlying acquisition is T1-weighted (19). For gradient-echo acquisitions, there are two strategies to generate T1-independent FF - the use of long repetition times (TR) and the use of low Flip Angles (20). Unfortunately, long TR values lengthen the acquisition and result in infeasible breath-hold acquisition times, particularly for three-dimensional (3D) gradient-echo imaging. The use of low Flip Angles to reduce T1 bias in liver imaging has been proposed by several authors (16,19,21). Specifically, for 3D techniques, Flip Angles of 5° for 1.5 Tesla (T) (15) and 3° for 3T (14) have been described and shown to effectively avoid T1 bias in fat quantification. However, the use of small Flip Angles leads to low signal-to-noise ratios (SNRs) of the underlying data. Several recent works have investigated this tradeoff between T1 bias and SNR in chemical shift-encoded fat quantification. Hines et al introduced a mathematical framework to design SNR-optimized chemical shift-encoded fat quantification acquisitions, given a maximum allowed T1 bias (20). Johnson et al investigated the T1 bias for liver fat quantification using combinations of different TRs (7/14 ms) and relatively low Flip Angles (1–5° for 3D imaging) (22). The errors due to T1 effects increased as a function of the Flip Angle. However, the use of high image Flip Angles increases the signal-to-noise (SNR). At this time, it is not clear whether this higher SNR is advantageous for liver fat quantification. An alternative approach for fat quantification free of T1 bias is to perform acquisitions with high Flip Angles (closer to the Ernst Angle), and correct for T1 bias by postprocessing, using either measured (23) or assumed T1 values for water and fat. This approach has been used successfully in the lumbar spine (23). The impact of SNR-optimized MRI on the noise performance of liver fat quantification (PDFF) and liver iron quantification (R2* mapping) is unknown. Therefore, the purpose of our study was to identify the optimal image Flip Angle for liver fat quantification while avoiding errors caused by T1 bias and errors resulting from low SNR. Furthermore, a simple reconstruction technique (20) was used to correct for T1 errors and to calculate an SNR-optimized T1-independent FF. A second purpose of this study was to determine whether the SNR of the underlying image data influences the estimation of R2*.
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effect of Flip Angle on the accuracy and repeatability of hepatic proton density fat fraction estimation by complex data based t1 independent t2 corrected spectrum modeled mri
Journal of Magnetic Resonance Imaging, 2014Co-Authors: Benjamin L Johnson, Gavin Hamilton, Anthony Gamst, Tanya Wolfson, Jeffrey B Schwimmer, Michael E Schroeder, Masoud Shiehmorteza, Rohit Loomba, Scott B ReederAbstract:Purpose To evaluate the effect of Flip Angle (FA) on accuracy and within-examination repeatability of hepatic proton-density fat fraction (PDFF) estimation with complex data-based magnetic resonance imaging (MRI).
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effects of refocusing Flip Angle modulation and view ordering in 3d fast spin echo
Magnetic Resonance in Medicine, 2008Co-Authors: Reed F Busse, Scott B Reeder, Anja C S Brau, Charles R Michelich, Ersin Bayram, Richard Kijowski, Howard A RowleyAbstract:Recent advances have reduced scan time in three-dimensional fast spin echo (3D-FSE) imaging, including very long echo trains through refocusing Flip Angle (FA) modulation and 2D-accelerated parallel imaging. This work describes a method to modulate refocusing FAs that produces sharp point spread functions (PSFs) from very long echo trains while exercising direct control over minimum, center-k-space, and maximum FAs in order to accommodate the presence of flow and motion, SNR requirements, and RF power limits. Additionally, a new method for ordering views to map signal modulation from the echo train into k(y)-k(z) space that enables nonrectangular k-space grids and autocalibrating 2D-accelerated parallel imaging is presented. With long echo trains and fewer echoes required to encode large matrices, large volumes with high in- and through-plane resolution matrices may be acquired with scan times of 3-6 min, as demonstrated for volumetric brain, knee, and kidney imaging.
Anthony Gamst - One of the best experts on this subject based on the ideXlab platform.
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effect of intravenous gadoxetate disodium and Flip Angle on hepatic proton density fat fraction estimation with six echo gradient recalled echo magnitude based mr imaging at 3t
Abdominal Radiology, 2017Co-Authors: Charlie C Park, Gavin Hamilton, Tanya Wolfson, Ajinkya Desai, Kevin A Zand, Jonathan Hooker, Eduardo A C Costa, Elhamy Heba, Lisa Clark, Anthony GamstAbstract:Purpose The aim of the study was to determine in patients undergoing gadoxetate disodium (Gx)-enhanced MR exams whether proton density fat fraction (PDFF) estimation accuracy of magnitude-based multi-gradient-echo MRI (MRI-M) could be improved by using high Flip Angle (FA) on post-contrast images.
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effect of intravenous gadoxetate disodium and Flip Angle on hepatic proton density fat fraction estimation with six echo gradient recalled echo magnitude based mr imaging at 3t
Abdominal Radiology, 2017Co-Authors: Charlie C Park, Gavin Hamilton, Tanya Wolfson, Ajinkya Desai, Kevin A Zand, Jonathan Hooker, Eduardo A C Costa, Elhamy Heba, Lisa Clark, Anthony GamstAbstract:The aim of the study was to determine in patients undergoing gadoxetate disodium (Gx)-enhanced MR exams whether proton density fat fraction (PDFF) estimation accuracy of magnitude-based multi-gradient-echo MRI (MRI-M) could be improved by using high Flip Angle (FA) on post-contrast images. Thirty-one adults with known or suspected hepatic steatosis undergoing 3T clinical Gx-enhanced liver MRI were enrolled prospectively. MR spectroscopy (MRS), the reference standard, was performed before Gx to measure MRS-PDFF. Low (10°)- and high (50°)-Flip Angle (FA) MRI-M sequences were acquired before and during the hepatobiliary phase after Gx administration; MRI-PDFF was estimated in the MRS-PDFF voxel location. Linear regression parameters (slope, intercept, average bias, R 2) were calculated for MRS-PDFF as a function of MRI-PDFF for each MRI-M sequence (pre-Gx low-FA, pre-Gx high-FA, post-Gx low-FA, post-Gx high-FA) for all patients and for patients with MRS-PDFF <10%. Regression parameters were compared (Bonferroni-adjusted bootstrap-based tests). Three of the four MRI-M sequences (pre-Gx low-FA, post-Gx low-FA, post-Gx high-FA) provided relatively unbiased PDFF estimates overall and in the low-PDFF range, with regression slopes close to 1 and intercepts and biases close to zero. Pre-Gx high-FA MRI overestimated PDFF in proportion to MRS-PDFF, with slopes of 0.72 (overall) and 0.63 (low-PDFF range). Based on regression bias closest to 0, the post-Gx high-FA sequence was the most accurate overall and in the low-PDFF range. This sequence provided statistically significant improvements in at least two regression parameters compared to every other sequence. In patients undergoing Gx-enhanced MR exams, PDFF estimation accuracy of MRI-M can be improved by using high-FA on post-contrast images.
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effect of Flip Angle on the accuracy and repeatability of hepatic proton density fat fraction estimation by complex data based t1 independent t2 corrected spectrum modeled mri
Journal of Magnetic Resonance Imaging, 2014Co-Authors: Benjamin L Johnson, Gavin Hamilton, Anthony Gamst, Tanya Wolfson, Jeffrey B Schwimmer, Michael E Schroeder, Masoud Shiehmorteza, Rohit Loomba, Scott B ReederAbstract:Purpose To evaluate the effect of Flip Angle (FA) on accuracy and within-examination repeatability of hepatic proton-density fat fraction (PDFF) estimation with complex data-based magnetic resonance imaging (MRI).
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nonalcoholic fatty liver disease diagnostic and fat grading accuracy of low Flip Angle multiecho gradient recalled echo mr imaging at 1 5 t
Radiology, 2009Co-Authors: Takeshi Yokoo, Mark Bydder, Gavin Hamilton, Michael S Middleton, Anthony Gamst, Tanya Wolfson, Tarek Hassanein, Heather Patton, Joel E Lavine, Jeffrey B SchwimmerAbstract:Purpose: To assess the accuracy of four fat quantification methods at low-Flip-Angle multiecho gradient-recalled-echo (GRE) magnetic resonance (MR) imaging in nonalcoholic fatty liver disease (NAFLD) by using MR spectroscopy as the reference standard. Materials and Methods: In this institutional review board–approved, HIPAA-compliant prospective study, 110 subjects (29 with biopsy-confirmed NAFLD, 50 overweight and at risk for NAFLD, and 31 healthy volunteers) (mean age, 32.6 years ± 15.6 [standard deviation]; range, 8–66 years) gave informed consent and underwent MR spectroscopy and GRE MR imaging of the liver. Spectroscopy involved a long repetition time (to suppress T1 effects) and multiple echo times (to estimate T2 effects); the reference fat fraction (FF) was calculated from T2-corrected fat and water spectral peak areas. Imaging involved a low Flip Angle (to suppress T1 effects) and multiple echo times (to estimate T2* effects); imaging FF was calculated by using four analysis methods of progressiv...
Eric Y Chang - One of the best experts on this subject based on the ideXlab platform.
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whole knee joint t1 values measured in vivo at 3t by combined 3d ultrashort echo time cones actual Flip Angle and variable Flip Angle methods
Magnetic Resonance in Medicine, 2019Co-Authors: Wei Zhao, Adam C Searleman, Hyungseok Jang, Eric Y Chang, Jiang DuAbstract:Author(s): Ma, Ya-Jun; Zhao, Wei; Wan, Lidi; Guo, Tan; Searleman, Adam; Jang, Hyungseok; Chang, Eric Y; Du, Jiang | Abstract: PURPOSE:To measure T1 relaxations for the major tissues in whole knee joints on a clinical 3T scanner. METHODS:The 3D UTE-Cones actual Flip Angle imaging (AFI) method was used to map the transmission radiofrequency field (B1 ) in both short and long T2 tissues, which was then used to correct the 3D UTE-Cones variable Flip Angle (VFA) fitting to generate accurate T1 maps. Numerical simulation was carried out to investigate the accuracy of T1 measurement for a range of T2 values, excitation pulse durations, and B1 errors. Then, the 3D UTE-Cones AFI-VFA method was applied to healthy volunteers (N = 16) to quantify the T1 of knee tissues including cartilage, meniscus, quadriceps tendon, patellar tendon, anterior cruciate ligament (ACL), posterior cruciate ligament (PCL), marrow, and muscles at 3T. RESULTS:Numerical simulation showed that the 3D UTE-Cones AFI-VFA technique can provide accurate T1 measurements (error l1%) when the tissue T2 is longer than 1 ms and a 150 μs excitation RF pulse is used and therefore is suitable for most knee joint tissues. The proposed 3D UTE-Cones AFI-VFA method showed an average T1 of 1098 ± 67 ms for cartilage, 833 ± 47 ms for meniscus, 800 ± 66 ms for quadriceps tendon, 656 ± 43 ms for patellar tendon, 873 ± 38 ms for ACL, 832 ± 49 ms for PCL, 379 ± 18 ms for marrow, and 1393 ± 46 ms for muscles. CONCLUSION:The 3D UTE-Cones AFI-VFA method allows volumetric T1 measurement of the major tissues in whole knee joints on a clinical 3T scanner.
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accurate t1 mapping of short t2 tissues using a three dimensional ultrashort echo time cones actual Flip Angle imaging variable repetition time 3d ute cones afi vtr method
Magnetic Resonance in Medicine, 2018Co-Authors: Michael Carl, Yanchun Zhu, Nikolaus M Szeverenyi, G M Bydder, Eric Y ChangAbstract:Author(s): Ma, Ya-Jun; Lu, Xing; Carl, Michael; Zhu, Yanchun; Szeverenyi, Nikolaus M; Bydder, Graeme M; Chang, Eric Y; Du, Jiang | Abstract: PurposeTo develop an accurate T1 measurement method for short T2 tissues using a combination of a 3-dimensional ultrashort echo time cones actual Flip Angle imaging technique and a variable repetition time technique (3D UTE-Cones AFI-VTR) on a clinical 3T scanner.MethodsFirst, the longitudinal magnetization mapping function of the excitation pulse was obtained with the 3D UTE-Cones AFI method, which provided information about excitation efficiency and B1 inhomogeneity. Then, the derived mapping function was substituted into the VTR fitting to generate accurate T1 maps. Numerical simulation and phantom studies were carried out to compare the AFI-VTR method with a B1 -uncorrected VTR method, a B1 -uncorrected variable Flip Angle (VFA) method, and a B1 -corrected VFA method. Finally, the 3D UTE-Cones AFI-VTR method was applied to bovine bone samples (N = 6) and healthy volunteers (N = 3) to quantify the T1 of cortical bone.ResultsNumerical simulation and phantom studies showed that the 3D UTE-Cones AFI-VTR technique provides more accurate measurement of the T1 of short T2 tissues than the B1 -uncorrected VTR and VFA methods or the B1 -corrected VFA method. The proposed 3D UTE-Cones AFI-VTR method showed a mean T1 of 240 ± 25 ms for bovine cortical bone and 218 ± 10 ms for the tibial midshaft of human volunteers, respectively, at 3 T.ConclusionThe 3D UTE-Cones AFI-VTR method can provide accurate T1 measurements of short T2 tissues such as cortical bone. Magn Reson Med 80:598-608, 2018. © 2018 International Society for Magnetic Resonance in Medicine.
Fuyuze Tokoglu - One of the best experts on this subject based on the ideXlab platform.
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dynamic Flip Angle ecg gating with nuisance signal regression improves resting state bold functional connectivity mapping by reducing cardiogenic noise
Magnetic Resonance in Medicine, 2019Co-Authors: Chenxi Hu, Fuyuze Tokoglu, Dustin Scheinost, Xilin Shen, Dana C Peters, Gigi Galiana, Todd R ConstableAbstract:Purpose To investigate an ECG-gated dynamic-Flip-Angle BOLD sequence with improved robustness against cardiogenic noise in resting-state fMRI. Methods ECG-gating minimizes the cardiogenic noise but introduces T1 -dependent signal variation, which is minimized by combination of a dynamic-Flip-Angle technique and retrospective nuisance signal regression (NSR) using signals of white matter, CSF, and global average. The technique was studied with simulations in a wide range of T1 and B1 fields and phantom imaging with pre-programmed TR variations. Resting-state fMRI of 20 healthy subjects was acquired with non-gated BOLD (NG), ECG-gated constant-Flip-Angle BOLD (GCFA), ECG-gated BOLD with retrospective T1 -correction (GRC), and ECG-gated dynamic-Flip-Angle BOLD (GDFA), all processed by the same NSR method. GDFA was compared to alternative methods over temporal SNR (tSNR), seed-based connectivity, and whole-brain voxelwise connectivity based on intrinsic connectivity distribution (ICD). A previous large-cohort data set (N = 100) was used as a connectivity gold standard. Results Simulations and phantom imaging show substantial reduction of the T1 -dependent signal variation with GDFA alone, and further reduction with NSR. The resting-state study shows improved tSNR in the basal brain, comparing GDFA to NG, after both processed with NSR. Furthermore, GDFA significantly improved subcortical-subcortical and cortical-subcortical connectivity for several representative seeds and significantly improved ICD in the brainstem, thalamus, striatum, and prefrontal cortex, compared to the other 3 approaches. Conclusion GDFA with NSR improves mapping of the resting-state functional connectivity of the basal-brain regions by reducing cardiogenic noise.
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dynamic Flip Angle ecg gating with nuisance signal regression improves resting state bold functional connectivity mapping by reducing cardiogenic noise
Magnetic Resonance in Medicine, 2019Co-Authors: Fuyuze Tokoglu, Maolin Qiu, Dustin Scheinost, Xilin Shen, Dana C Peters, Gigi Galiana, Todd R ConstableAbstract:Purpose To investigate an ECG-gated dynamic-Flip-Angle BOLD sequence with improved robustness against cardiogenic noise in resting-state fMRI. Methods ECG-gating minimizes the cardiogenic noise but introduces T1 -dependent signal variation, which is minimized by combination of a dynamic-Flip-Angle technique and retrospective nuisance signal regression (NSR) using signals of white matter, CSF, and global average. The technique was studied with simulations in a wide range of T1 and B1 fields and phantom imaging with pre-programmed TR variations. Resting-state fMRI of 20 healthy subjects was acquired with non-gated BOLD (NG), ECG-gated constant-Flip-Angle BOLD (GCFA), ECG-gated BOLD with retrospective T1 -correction (GRC), and ECG-gated dynamic-Flip-Angle BOLD (GDFA), all processed by the same NSR method. GDFA was compared to alternative methods over temporal SNR (tSNR), seed-based connectivity, and whole-brain voxelwise connectivity based on intrinsic connectivity distribution (ICD). A previous large-cohort data set (N = 100) was used as a connectivity gold standard. Results Simulations and phantom imaging show substantial reduction of the T1 -dependent signal variation with GDFA alone, and further reduction with NSR. The resting-state study shows improved tSNR in the basal brain, comparing GDFA to NG, after both processed with NSR. Furthermore, GDFA significantly improved subcortical-subcortical and cortical-subcortical connectivity for several representative seeds and significantly improved ICD in the brainstem, thalamus, striatum, and prefrontal cortex, compared to the other 3 approaches. Conclusion GDFA with NSR improves mapping of the resting-state functional connectivity of the basal-brain regions by reducing cardiogenic noise.
