The Experts below are selected from a list of 34347 Experts worldwide ranked by ideXlab platform
Eric C Wong - One of the best experts on this subject based on the ideXlab platform.
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multiPhase pseudocontinuous arterial spin labeling mp pcasl for robust quantification of cerebral blood flow
Magnetic Resonance in Medicine, 2010Co-Authors: Youngkyoo Jung, Eric C WongAbstract:Pseudocontinuous arterial spin labeling (PCASL) has been demonstrated to provide the sensitivity of the continuous arterial spin labeling method while overcoming many of the limitations of that method. Because the specification of the Phases in the radiofrequency pulse train in PCASL defines the tag and control conditions of the flowing arterial blood, its tagging efficiency is sensitive to factors, such as off-resonance fields, that induce Phase mismatches between the radiofrequency pulses and the flowing spins. As a result, the quantitative estimation of cerebral blood flow with PCASL can exhibit a significant amount of error when these factors are not taken into account. In this paper, the sources of the tagging efficiency loss are characterized and a novel PCASL method that utilizes multiple Phase Offsets is proposed to reduce the tagging efficiency loss in PCASL. Simulations are performed to evaluate the feasibility and the performance of the proposed method. Quantitative estimates of cerebral blood flow obtained with multiple Phase Offset PCASL are compared to estimates obtained with conventional PCASL and pulsed arterial spin labeling. Our results show that multiple Phase Offset PCASL provides robust cerebral blood flow quantification while retaining much of the sensitivity advantage of PCASL. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.
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multiPhase pseudocontinuous arterial spin labeling mp pcasl for robust quantification of cerebral blood flow
Magnetic Resonance in Medicine, 2010Co-Authors: Youngkyoo Jung, Eric C Wong, Thomas T LiuAbstract:Pseudocontinuous arterial spin labeling (PCASL) has been demonstrated to provide the sensitivity of the continuous arterial spin labeling method while overcoming many of the limitations of that method. Because the specification of the Phases in the radiofrequency pulse train in PCASL defines the tag and control conditions of the flowing arterial blood, its tagging efficiency is sensitive to factors, such as off-resonance fields, that induce Phase mismatches between the radiofrequency pulses and the flowing spins. As a result, the quantitative estimation of cerebral blood flow with PCASL can exhibit a significant amount of error when these factors are not taken into account. In this paper, the sources of the tagging efficiency loss are characterized and a novel PCASL method that utilizes multiple Phase Offsets is proposed to reduce the tagging efficiency loss in PCASL. Simulations are performed to evaluate the feasibility and the performance of the proposed method. Quantitative estimates of cerebral blood flow obtained with multiple Phase Offset PCASL are compared to estimates obtained with conventional PCASL and pulsed arterial spin labeling. Our results show that multiple Phase Offset PCASL provides robust cerebral blood flow quantification while retaining much of the sensitivity advantage of PCASL.
Youngkyoo Jung - One of the best experts on this subject based on the ideXlab platform.
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multiPhase pseudocontinuous arterial spin labeling mp pcasl for robust quantification of cerebral blood flow
Magnetic Resonance in Medicine, 2010Co-Authors: Youngkyoo Jung, Eric C WongAbstract:Pseudocontinuous arterial spin labeling (PCASL) has been demonstrated to provide the sensitivity of the continuous arterial spin labeling method while overcoming many of the limitations of that method. Because the specification of the Phases in the radiofrequency pulse train in PCASL defines the tag and control conditions of the flowing arterial blood, its tagging efficiency is sensitive to factors, such as off-resonance fields, that induce Phase mismatches between the radiofrequency pulses and the flowing spins. As a result, the quantitative estimation of cerebral blood flow with PCASL can exhibit a significant amount of error when these factors are not taken into account. In this paper, the sources of the tagging efficiency loss are characterized and a novel PCASL method that utilizes multiple Phase Offsets is proposed to reduce the tagging efficiency loss in PCASL. Simulations are performed to evaluate the feasibility and the performance of the proposed method. Quantitative estimates of cerebral blood flow obtained with multiple Phase Offset PCASL are compared to estimates obtained with conventional PCASL and pulsed arterial spin labeling. Our results show that multiple Phase Offset PCASL provides robust cerebral blood flow quantification while retaining much of the sensitivity advantage of PCASL. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.
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multiPhase pseudocontinuous arterial spin labeling mp pcasl for robust quantification of cerebral blood flow
Magnetic Resonance in Medicine, 2010Co-Authors: Youngkyoo Jung, Eric C Wong, Thomas T LiuAbstract:Pseudocontinuous arterial spin labeling (PCASL) has been demonstrated to provide the sensitivity of the continuous arterial spin labeling method while overcoming many of the limitations of that method. Because the specification of the Phases in the radiofrequency pulse train in PCASL defines the tag and control conditions of the flowing arterial blood, its tagging efficiency is sensitive to factors, such as off-resonance fields, that induce Phase mismatches between the radiofrequency pulses and the flowing spins. As a result, the quantitative estimation of cerebral blood flow with PCASL can exhibit a significant amount of error when these factors are not taken into account. In this paper, the sources of the tagging efficiency loss are characterized and a novel PCASL method that utilizes multiple Phase Offsets is proposed to reduce the tagging efficiency loss in PCASL. Simulations are performed to evaluate the feasibility and the performance of the proposed method. Quantitative estimates of cerebral blood flow obtained with multiple Phase Offset PCASL are compared to estimates obtained with conventional PCASL and pulsed arterial spin labeling. Our results show that multiple Phase Offset PCASL provides robust cerebral blood flow quantification while retaining much of the sensitivity advantage of PCASL.
Matthias A Dieringer - One of the best experts on this subject based on the ideXlab platform.
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flow measurement by cardiovascular magnetic resonance a multi centre multi vendor study of background Phase Offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements
Journal of Cardiovascular Magnetic Resonance, 2010Co-Authors: Peter D Gatehouse, Mark B M Hofman, Marijn P Rolf, Martin J Graves, John J Totman, Beat Werner, Rebecca A Quest, Yingmin Liu, Jochen Von Spiczak, Matthias A DieringerAbstract:Aims: Cardiovascular magnetic resonance (CMR) allows non-invasive Phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small Offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the Offset error. We studied the severity of uncorrected velocity Offset errors across sites and CMR systems. Methods and Results: In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated Phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No postprocessing corrections of Offsets were implemented. The greatest uncorrected velocity Offset, taken as an average over a ‘great vessel’ region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity Offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement. Conclusion: In the absence of hardware or software upgrades able to reduce Phase Offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of Offset correction software will still need testing with respect to clinical flow acquisitions.
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flow measurement by cardiovascular magnetic resonance a multi centre multi vendor study of background Phase Offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements
Journal of Cardiovascular Magnetic Resonance, 2010Co-Authors: Peter D Gatehouse, Mark B M Hofman, Marijn P Rolf, Martin J Graves, John J Totman, Beat Werner, Rebecca A Quest, Yingmin Liu, Jochen Von Spiczak, Matthias A DieringerAbstract:Cardiovascular magnetic resonance (CMR) allows non-invasive Phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small Offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the Offset error. We studied the severity of uncorrected velocity Offset errors across sites and CMR systems. In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated Phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of Offsets were implemented. The greatest uncorrected velocity Offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity Offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement. In the absence of hardware or software upgrades able to reduce Phase Offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of Offset correction software will still need testing with respect to clinical flow acquisitions.
Thomas T Liu - One of the best experts on this subject based on the ideXlab platform.
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multiPhase pseudocontinuous arterial spin labeling mp pcasl for robust quantification of cerebral blood flow
Magnetic Resonance in Medicine, 2010Co-Authors: Youngkyoo Jung, Eric C Wong, Thomas T LiuAbstract:Pseudocontinuous arterial spin labeling (PCASL) has been demonstrated to provide the sensitivity of the continuous arterial spin labeling method while overcoming many of the limitations of that method. Because the specification of the Phases in the radiofrequency pulse train in PCASL defines the tag and control conditions of the flowing arterial blood, its tagging efficiency is sensitive to factors, such as off-resonance fields, that induce Phase mismatches between the radiofrequency pulses and the flowing spins. As a result, the quantitative estimation of cerebral blood flow with PCASL can exhibit a significant amount of error when these factors are not taken into account. In this paper, the sources of the tagging efficiency loss are characterized and a novel PCASL method that utilizes multiple Phase Offsets is proposed to reduce the tagging efficiency loss in PCASL. Simulations are performed to evaluate the feasibility and the performance of the proposed method. Quantitative estimates of cerebral blood flow obtained with multiple Phase Offset PCASL are compared to estimates obtained with conventional PCASL and pulsed arterial spin labeling. Our results show that multiple Phase Offset PCASL provides robust cerebral blood flow quantification while retaining much of the sensitivity advantage of PCASL.
Yingmin Liu - One of the best experts on this subject based on the ideXlab platform.
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a method to correct background Phase Offset for Phase contrast mri in the presence of steady flow and spatial wrap around artifact
Magnetic Resonance in Medicine, 2019Co-Authors: Aaron Pruitt, Yingmin Liu, Ning Jin, Orlando P Simonetti, Rizwan AhmadAbstract:Purpose Background Phase Offsets in Phase-contrast MRI are often corrected using polynomial regression; however, correction performance degrades when temporally invariant outliers such as steady flow or spatial wrap-around artifact are present. We describe and validate an iterative method called automatic rejection of temporally invariant outliers (ARTO), which excludes these outliers from the fitting process. Methods The ARTO method iteratively removes pixels with large polynomial regression errors analyzed by a Gaussian mixture model fitting of the residual distribution. A total of 150 trials of a simulated phantom (75 with wrap-around artifact) and 125 Phase-contrast MRI cines from 22 healthy subjects (48 with wrap-around artifact) were used for validation. Background Phase Offsets were corrected using second-order weighted regularized least squares (WRLS) with and without ARTO. Flow volumes after WRLS and WRLS+ARTO corrections were compared with the known truth (phantom) and stationary phantom reference (in vivo) using Bland-Altman analysis. The ratio between the pulmonary flow and the systemic flow was also computed in a subset of 6 subjects. Results In the simulated phantom, compared with WRLS and no correction, correction with WRLS+ARTO produced superior agreement in volumetric flow quantification with the known truth. In vivo, WRLS+ARTO also produced superior agreement with stationary phantom-corrected volumetric flow compared with WRLS and no correction. In data sets with wrap-around artifact, WRLS produced significantly larger variance in the pulmonary flow and systemic flow ratio than stationary phantom correction (P = .0008). Conclusion The proposed method provides automatic exclusion of temporally invariant outliers and produces flow quantification results comparable to stationary phantom correction.
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flow measurement by cardiovascular magnetic resonance a multi centre multi vendor study of background Phase Offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements
Journal of Cardiovascular Magnetic Resonance, 2010Co-Authors: Peter D Gatehouse, Mark B M Hofman, Marijn P Rolf, Martin J Graves, John J Totman, Beat Werner, Rebecca A Quest, Yingmin Liu, Jochen Von Spiczak, Matthias A DieringerAbstract:Aims: Cardiovascular magnetic resonance (CMR) allows non-invasive Phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small Offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the Offset error. We studied the severity of uncorrected velocity Offset errors across sites and CMR systems. Methods and Results: In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated Phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No postprocessing corrections of Offsets were implemented. The greatest uncorrected velocity Offset, taken as an average over a ‘great vessel’ region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity Offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement. Conclusion: In the absence of hardware or software upgrades able to reduce Phase Offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of Offset correction software will still need testing with respect to clinical flow acquisitions.
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flow measurement by cardiovascular magnetic resonance a multi centre multi vendor study of background Phase Offset errors that can compromise the accuracy of derived regurgitant or shunt flow measurements
Journal of Cardiovascular Magnetic Resonance, 2010Co-Authors: Peter D Gatehouse, Mark B M Hofman, Marijn P Rolf, Martin J Graves, John J Totman, Beat Werner, Rebecca A Quest, Yingmin Liu, Jochen Von Spiczak, Matthias A DieringerAbstract:Cardiovascular magnetic resonance (CMR) allows non-invasive Phase contrast measurements of flow through planes transecting large vessels. However, some clinically valuable applications are highly sensitive to errors caused by small Offsets of measured velocities if these are not adequately corrected, for example by the use of static tissue or static phantom correction of the Offset error. We studied the severity of uncorrected velocity Offset errors across sites and CMR systems. In a multi-centre, multi-vendor study, breath-hold through-plane retrospectively ECG-gated Phase contrast acquisitions, as are used clinically for aortic and pulmonary flow measurement, were applied to static gelatin phantoms in twelve 1.5 T CMR systems, using a velocity encoding range of 150 cm/s. No post-processing corrections of Offsets were implemented. The greatest uncorrected velocity Offset, taken as an average over a 'great vessel' region (30 mm diameter) located up to 70 mm in-plane distance from the magnet isocenter, ranged from 0.4 cm/s to 4.9 cm/s. It averaged 2.7 cm/s over all the planes and systems. By theoretical calculation, a velocity Offset error of 0.6 cm/s (representing just 0.4% of a 150 cm/s velocity encoding range) is barely acceptable, potentially causing about 5% miscalculation of cardiac output and up to 10% error in shunt measurement. In the absence of hardware or software upgrades able to reduce Phase Offset errors, all the systems tested appeared to require post-acquisition correction to achieve consistently reliable breath-hold measurements of flow. The effectiveness of Offset correction software will still need testing with respect to clinical flow acquisitions.