The Experts below are selected from a list of 2622 Experts worldwide ranked by ideXlab platform
Kohsuke Kudo - One of the best experts on this subject based on the ideXlab platform.
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evaluation of Oxygen Extraction Fraction in systemic lupus erythematosus patients using quantitative susceptibility mapping
Journal of Cerebral Blood Flow and Metabolism, 2019Co-Authors: Mari Miyata, Yi Wang, Kohsuke Kudo, Shingo Kakeda, Shigeru Iwata, Yoshiya Tanaka, Yukunori KorogiAbstract:The purposes of this study are to assess the Oxygen Extraction Fraction (OEF) changes on MRI-based quantitative susceptibility mapping (QSM) in systemic lupus erythematosus (SLE) patients and to de...
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preoperative cerebral Oxygen Extraction Fraction imaging generated from 7t mr quantitative susceptibility mapping predicts development of cerebral hyperperfusion following carotid endarterectomy
American Journal of Neuroradiology, 2017Co-Authors: Junichi Nomura, Ikuko Uwano, Makoto Sasaki, Kohsuke Kudo, Fumio Yamashita, S Fujiwara, Masakazu Kobayashi, Kuniaki OgasawaraAbstract:BACKGROUND AND PURPOSE: Preoperative hemodynamic impairment in the affected cerebral hemisphere is associated with the development of cerebral hyperperfusion following carotid endarterectomy. Cerebral Oxygen Extraction Fraction images generated from 7T MR quantitative susceptibility mapping correlate with Oxygen Extraction Fraction images on positron-emission tomography. The present study aimed to determine whether preoperative Oxygen Extraction Fraction imaging generated from 7T MR quantitative susceptibility mapping could identify patients at risk for cerebral hyperperfusion following carotid endarterectomy. MATERIALS AND METHODS: Seventy-seven patients with unilateral internal carotid artery stenosis (≥70%) underwent preoperative 3D T2*-weighted imaging using a multiple dipole-inversion algorithm with a 7T MR imager. Quantitative susceptibility mapping images were then obtained, and Oxygen Extraction Fraction maps were generated. Quantitative brain perfusion single-photon emission CT was also performed before and immediately after carotid endarterectomy. ROIs were automatically placed in the bilateral middle cerebral artery territories in all images using a 3D stereotactic ROI template, and affected-to-contralateral ratios in the ROIs were calculated on quantitative susceptibility mapping–Oxygen Extraction Fraction images. RESULTS: Ten patients (13%) showed post-carotid endarterectomy hyperperfusion (cerebral blood flow increases of ≥100% compared with preoperative values in the ROIs on brain perfusion SPECT). Multivariate analysis showed that a high quantitative susceptibility mapping–Oxygen Extraction Fraction ratio was significantly associated with the development of post-carotid endarterectomy hyperperfusion (95% confidence interval, 33.5–249.7; P = .002). Sensitivity, specificity, and positive- and negative-predictive values of the quantitative susceptibility mapping–Oxygen Extraction Fraction ratio for the prediction of the development of post-carotid endarterectomy hyperperfusion were 90%, 84%, 45%, and 98%, respectively. CONCLUSIONS: Preoperative Oxygen Extraction Fraction imaging generated from 7T MR quantitative susceptibility mapping identifies patients at risk for cerebral hyperperfusion following carotid endarterectomy.
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noninvasive assessment of Oxygen Extraction Fraction in chronic ischemia using quantitative susceptibility mapping at 7 tesla
Stroke, 2017Co-Authors: Ikuko Uwano, Junichi Nomura, Kohsuke Kudo, Fumio Yamashita, Kuniaki Ogasawara, Ryota Sato, Hiroyuki Kameda, Futoshi Mori, Kunihiro Yoshioka, Makoto SasakiAbstract:Background and Purpose— The Oxygen Extraction Fraction (OEF) is an effective metric to evaluate metabolic reserve in chronic ischemia. However, OEF is considered to be accurately measured only when using positron emission tomography (PET). Thus, we investigated whether OEF maps generated by magnetic resonance quantitative susceptibility mapping (QSM) at 7 Tesla enabled detection of OEF changes when compared with those obtained with PET. Methods— Forty-one patients with chronic stenosis/occlusion of the unilateral internal carotid artery or middle cerebral artery were examined using 7 Tesla-MRI and PET scanners. QSM images were obtained from 3-dimensional T2*-weighted images, using a multiple dipole-inversion algorithm. OEF maps were generated based on susceptibility differences between venous structures and brain tissues on QSM images. OEF ratios of the ipsilateral middle cerebral artery territory against the contralateral side were calculated on the QSM-OEF and PET-OEF images, using an anatomic template. Results— The OEF ratio in the middle cerebral artery territory showed significant correlations between QSM-OEF and PET-OEF maps ( r =0.69; P r =0.79; P =0.004), although showing significant systematic biases for the agreements. An increased QSM-OEF ratio of >1.09, as determined by receiver operating characteristic analysis, showed a sensitivity and specificity of 0.82 and 0.86, respectively, for the substantial increase in the PET-OEF ratio. Absolute QSM-OEF values were significantly correlated with PET-OEF values in the patients with increased PET-OEF. Conclusions— OEF ratios on QSM-OEF images at 7 Tesla showed a good correlation with those on PET-OEF images in patients with unilateral steno-occlusive internal carotid artery/middle cerebral artery lesions, suggesting that noninvasive OEF measurement by MRI can be a substitute for PET.
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Oxygen Extraction Fraction measurement using quantitative susceptibility mapping comparison with positron emission tomography
Journal of Cerebral Blood Flow and Metabolism, 2016Co-Authors: Yi Wang, Ikuko Uwano, Kohsuke Kudo, Fumio Yamashita, Kuniaki Ogasawara, Toshiyuki Murakami, Jonathan Goodwin, Satomi Higuchi, Akira OgawaAbstract:The purposes of this study are to establish Oxygen Extraction Fraction (OEF) measurements using quantitative susceptibility mapping (QSM) of magnetic resonance imaging (MRI), and to compare QSM–OEF data with the gold standard 15O positron emission tomography (PET). Twenty-six patients with chronic unilateral internal carotid artery or middle cerebral artery stenosis or occlusion, and 15 normal subjects were included. MRI scans were conducted using a 3.0 Tesla scanner with a three-dimensional spoiled gradient recalled sequence. QSM images were created using the morphology-enabled dipole inversion method, and OEF maps were generated from QSM images using Extraction of venous susceptibility induced by deOxygenated hemoglobin. Significant correlation of relative OEF ratio to contra-lateral hemisphere between QSM–OEF and PET–OEF was observed (r = 0.62, p < 0.001). The local (intra-section) correlation was also significant (r = 0.52, p < 0.001) in patients with increased PET–OEF. The sensitivity and specificity...
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Oxygen Extraction Fraction measurement using quantitative susceptibility mapping: Comparison with positron emission tomography:
Journal of Cerebral Blood Flow and Metabolism, 2015Co-Authors: Kohsuke Kudo, Yi Wang, Ikuko Uwano, Fumio Yamashita, Kuniaki Ogasawara, Toshiyuki Murakami, Jonathan Goodwin, Satomi Higuchi, Akira OgawaAbstract:The purposes of this study are to establish Oxygen Extraction Fraction (OEF) measurements using quantitative susceptibility mapping (QSM) of magnetic resonance imaging (MRI), and to compare QSM–OEF data with the gold standard 15O positron emission tomography (PET). Twenty-six patients with chronic unilateral internal carotid artery or middle cerebral artery stenosis or occlusion, and 15 normal subjects were included. MRI scans were conducted using a 3.0 Tesla scanner with a three-dimensional spoiled gradient recalled sequence. QSM images were created using the morphology-enabled dipole inversion method, and OEF maps were generated from QSM images using Extraction of venous susceptibility induced by deOxygenated hemoglobin. Significant correlation of relative OEF ratio to contra-lateral hemisphere between QSM–OEF and PET–OEF was observed (r = 0.62, p
Makoto Sasaki - One of the best experts on this subject based on the ideXlab platform.
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preoperative cerebral Oxygen Extraction Fraction imaging generated from 7t mr quantitative susceptibility mapping predicts development of cerebral hyperperfusion following carotid endarterectomy
American Journal of Neuroradiology, 2017Co-Authors: Junichi Nomura, Ikuko Uwano, Makoto Sasaki, Kohsuke Kudo, Fumio Yamashita, S Fujiwara, Masakazu Kobayashi, Kuniaki OgasawaraAbstract:BACKGROUND AND PURPOSE: Preoperative hemodynamic impairment in the affected cerebral hemisphere is associated with the development of cerebral hyperperfusion following carotid endarterectomy. Cerebral Oxygen Extraction Fraction images generated from 7T MR quantitative susceptibility mapping correlate with Oxygen Extraction Fraction images on positron-emission tomography. The present study aimed to determine whether preoperative Oxygen Extraction Fraction imaging generated from 7T MR quantitative susceptibility mapping could identify patients at risk for cerebral hyperperfusion following carotid endarterectomy. MATERIALS AND METHODS: Seventy-seven patients with unilateral internal carotid artery stenosis (≥70%) underwent preoperative 3D T2*-weighted imaging using a multiple dipole-inversion algorithm with a 7T MR imager. Quantitative susceptibility mapping images were then obtained, and Oxygen Extraction Fraction maps were generated. Quantitative brain perfusion single-photon emission CT was also performed before and immediately after carotid endarterectomy. ROIs were automatically placed in the bilateral middle cerebral artery territories in all images using a 3D stereotactic ROI template, and affected-to-contralateral ratios in the ROIs were calculated on quantitative susceptibility mapping–Oxygen Extraction Fraction images. RESULTS: Ten patients (13%) showed post-carotid endarterectomy hyperperfusion (cerebral blood flow increases of ≥100% compared with preoperative values in the ROIs on brain perfusion SPECT). Multivariate analysis showed that a high quantitative susceptibility mapping–Oxygen Extraction Fraction ratio was significantly associated with the development of post-carotid endarterectomy hyperperfusion (95% confidence interval, 33.5–249.7; P = .002). Sensitivity, specificity, and positive- and negative-predictive values of the quantitative susceptibility mapping–Oxygen Extraction Fraction ratio for the prediction of the development of post-carotid endarterectomy hyperperfusion were 90%, 84%, 45%, and 98%, respectively. CONCLUSIONS: Preoperative Oxygen Extraction Fraction imaging generated from 7T MR quantitative susceptibility mapping identifies patients at risk for cerebral hyperperfusion following carotid endarterectomy.
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noninvasive assessment of Oxygen Extraction Fraction in chronic ischemia using quantitative susceptibility mapping at 7 tesla
Stroke, 2017Co-Authors: Ikuko Uwano, Junichi Nomura, Kohsuke Kudo, Fumio Yamashita, Kuniaki Ogasawara, Ryota Sato, Hiroyuki Kameda, Futoshi Mori, Kunihiro Yoshioka, Makoto SasakiAbstract:Background and Purpose— The Oxygen Extraction Fraction (OEF) is an effective metric to evaluate metabolic reserve in chronic ischemia. However, OEF is considered to be accurately measured only when using positron emission tomography (PET). Thus, we investigated whether OEF maps generated by magnetic resonance quantitative susceptibility mapping (QSM) at 7 Tesla enabled detection of OEF changes when compared with those obtained with PET. Methods— Forty-one patients with chronic stenosis/occlusion of the unilateral internal carotid artery or middle cerebral artery were examined using 7 Tesla-MRI and PET scanners. QSM images were obtained from 3-dimensional T2*-weighted images, using a multiple dipole-inversion algorithm. OEF maps were generated based on susceptibility differences between venous structures and brain tissues on QSM images. OEF ratios of the ipsilateral middle cerebral artery territory against the contralateral side were calculated on the QSM-OEF and PET-OEF images, using an anatomic template. Results— The OEF ratio in the middle cerebral artery territory showed significant correlations between QSM-OEF and PET-OEF maps ( r =0.69; P r =0.79; P =0.004), although showing significant systematic biases for the agreements. An increased QSM-OEF ratio of >1.09, as determined by receiver operating characteristic analysis, showed a sensitivity and specificity of 0.82 and 0.86, respectively, for the substantial increase in the PET-OEF ratio. Absolute QSM-OEF values were significantly correlated with PET-OEF values in the patients with increased PET-OEF. Conclusions— OEF ratios on QSM-OEF images at 7 Tesla showed a good correlation with those on PET-OEF images in patients with unilateral steno-occlusive internal carotid artery/middle cerebral artery lesions, suggesting that noninvasive OEF measurement by MRI can be a substitute for PET.
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susceptibility weighted phase imaging and Oxygen Extraction Fraction measurement during sedation and sedation recovery using 7t mri
Journal of Neuroimaging, 2015Co-Authors: Ikuko Uwano, Kohsuke Kudo, Fumio Yamashita, Jonathan Goodwin, Satomi Higuchi, Yutaka Shinohe, Makoto SasakiAbstract:BACKGROUND & PURPOSE In this work, we demonstrate Oxygen Extraction Fraction (OEF) measurement using 7T MRI with susceptibility-weighted imaging (SWI), in sedated and nonsedated adults. METHODS Ten healthy subjects (30.3 ± 4.5 years, 9 men, 1 woman) formed control (n = 5) and sedation groups (n = 5). Midazolam and propofol injection was administered to the same sedation group subjects during 2 different scanning sessions. Two-dimensional SPGR imaging was performed before, during, and twice after (propofol, +10, +30 minutes; midazolam, +10, +40 minutes) conscious sedation. The equivalent procedure was performed with the control group without sedation. After SWI analysis, change in OEF between scans was quantified, and parcelated ΔOEF maps were generated with 77 gray matter (GM)-containing volumes-of-interest (VOIs). RESULTS Significant decreases in OEF were shown in 14 GM VOIs during sedation relative to the control group, most notably during midazolam sedation (P < .05). In contrast, no significant decrease was observed after 10 minutes and in only 4 VOIs after 40 minutes recovery. CONCLUSION Significant change in ΔOEF during conscious sedation using midazolam and propofol could be measured using SWI at 7T in vivo. This may be a potentially useful approach for the noninvasive assessment of OEF in the brain on a clinical basis.
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mapping of cerebral Oxygen Extraction Fraction changes with susceptibility weighted phase imaging
Radiology, 2011Co-Authors: Yuri Zaitsu, Makoto Sasaki, Kohsuke Kudo, Satoshi Terae, Rie Yazu, Kinya Ishizaka, Noriyuki Fujima, Mark E Haacke, Hiroki ShiratoAbstract:Maps of the Oxygen Extraction Fraction (OEF) change obtained showed that the changes in OEF corresponded to anticipated change in cerebral blood flow induced by various conditions and might be used in the future to evaluate cerebrovascular and other cerebral disorders in which changes in Oxygen metabolism are important for evaluating therapeutic strategies.
Peter C M Van Zijl - One of the best experts on this subject based on the ideXlab platform.
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measurement of parenchymal extravascular r2 and tissue Oxygen Extraction Fraction using multi echo vaso mri at 7 tesla
NMR in Biomedicine, 2015Co-Authors: Ying Cheng, Peter C M Van ZijlAbstract:Parenchymal extravascular R2* is an important parameter for quantitative blood-Oxygenation-level-dependent (BOLD) studies. Total and intravascular R2* values and changes in R2* values during functional stimulations have been reported in a number of studies. The purpose of this study was to measure absolute extravascular R2* values in human visual cortex and estimate the intra- and extravascular contributions in the BOLD effect at 7T. Vascular-space-occupancy (VASO) MRI was employed to separate out the extravascular tissue signal. Multi-echo VASO and BOLD fMRI with visual stimulation were performed at 7T for R2* measurement at a spatial resolution of 2.5×2.5×2.5 mm3 in healthy volunteers (n = 6). The ratio of changes in extravascular and total R2* (ΔR2*) was used to estimate the extravascular Fraction of the BOLD effect. Extravascular R2* were found to be 44.66 ± 1.55 s−1 and 43.38 ± 1.51 s−1 (mean ± SEM, n = 6) at rest and activation, respectively, in human visual cortex at 7T. The extravascular BOLD Fraction was estimated to be 91 ± 3%. Parenchymal Oxygen Extraction Fraction (OEF) during activation was estimated to be 0.24 ± 0.01 based on the R2*measurements, indicating an approximately 37% decrease compared to OEF at rest.
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measurement of parenchymal extravascular r2 and tissue Oxygen Extraction Fraction using multi echo vascular space occupancy mri at 7 t
NMR in Biomedicine, 2015Co-Authors: Ying Cheng, Peter C M Van ZijlAbstract:Parenchymal extravascular R2* is an important parameter for quantitative blood Oxygenation level-dependent (BOLD) studies. Total and intravascular R2* values and changes in R2* values during functional stimulations have been reported in a number of studies. The purpose of this study was to measure absolute extravascular R2* values in human visual cortex and to estimate the intra- and extravascular contributions to the BOLD effect at 7 T. Vascular space occupancy (VASO) MRI was employed to separate out the extravascular tissue signal. Multi-echo VASO and BOLD functional MRI (fMRI) with visual stimulation were performed at 7 T for R2* measurement at a spatial resolution of 2.5 × 2.5 × 2.5 mm3 in healthy volunteers (n = 6). The ratio of changes in extravascular and total R2* (ΔR2*) was used to estimate the extravascular Fraction of the BOLD effect. Extravascular R2* values were found to be 44.66 ± 1.55 and 43.38 ± 1.51 s–1 (mean ± standard error of the mean, n = 6) at rest and activation, respectively, in human visual cortex at 7 T. The extravascular BOLD Fraction was estimated to be 91 ± 3%. The parenchymal Oxygen Extraction Fraction (OEF) during activation was estimated to be 0.24 ± 0.01 based on the R2* measurements, indicating an approximately 37% decrease compared with OEF at rest. Copyright © 2014 John Wiley & Sons, Ltd.
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Measurement of parenchymal extravascularR2* and tissue Oxygen Extraction Fraction using multi-echo vascular space occupancy MRI at 7 T: MEASUREMENT OF EXTRAVASCULAR BOLD EFFECTS AT 7 T
NMR in Biomedicine, 2014Co-Authors: Ying Cheng, Peter C M Van ZijlAbstract:Parenchymal extravascular R2* is an important parameter for quantitative blood-Oxygenation-level-dependent (BOLD) studies. Total and intravascular R2* values and changes in R2* values during functional stimulations have been reported in a number of studies. The purpose of this study was to measure absolute extravascular R2* values in human visual cortex and estimate the intra- and extravascular contributions in the BOLD effect at 7T. Vascular-space-occupancy (VASO) MRI was employed to separate out the extravascular tissue signal. Multi-echo VASO and BOLD fMRI with visual stimulation were performed at 7T for R2* measurement at a spatial resolution of 2.5×2.5×2.5 mm3 in healthy volunteers (n = 6). The ratio of changes in extravascular and total R2* (ΔR2*) was used to estimate the extravascular Fraction of the BOLD effect. Extravascular R2* were found to be 44.66 ± 1.55 s−1 and 43.38 ± 1.51 s−1 (mean ± SEM, n = 6) at rest and activation, respectively, in human visual cortex at 7T. The extravascular BOLD Fraction was estimated to be 91 ± 3%. Parenchymal Oxygen Extraction Fraction (OEF) during activation was estimated to be 0.24 ± 0.01 based on the R2*measurements, indicating an approximately 37% decrease compared to OEF at rest.
Hanzhang Lu - One of the best experts on this subject based on the ideXlab platform.
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Validation of T2 -based Oxygen Extraction Fraction measurement with 15 O positron emission tomography
Magnetic Resonance in Medicine, 2020Co-Authors: Dengrong Jiang, Shengwen Deng, Crystal Franklin, Michael O'boyle, Wei Zhang, Betty L. Heyl, Paul A Jerabek, Hanzhang LuAbstract:PURPOSE To evaluate the accuracy of T2 -based whole-brain Oxygen Extraction Fraction (OEF) estimation by comparing it with gold standard 15 O-PET measurements. METHODS Sixteen healthy adult subjects underwent MRI and 15 O-PET OEF measurements on the same day. On MRI, whole-brain OEF was quantified by T2 -relaxation-under-spin-tagging (TRUST) MRI, based on subject-specific hematocrit. The TRUST OEF was compared to the whole-brain averaged OEF produced by 15 O-PET. Agreement between TRUST and 15 O-PET whole-brain OEF measurements was examined in terms of intraclass correlation coefficient (ICC) and in absolute OEF values. In a subset of 10 subjects, test-retest reproducibility of whole-brain OEF was also evaluated and compared between the two modalities. RESULTS Across the 16 subjects, the mean whole-brain OEF of TRUST and 15 O-PET were 36.44 ± 4.07% and 36.45 ± 3.65%, respectively, showing no difference between the two modalities (P = .99). TRUST whole-brain OEF strongly correlated with that of 15 O-PET (N = 16, ICC = 0.90, P = 4 × 10-7 ). The coefficient-of-variation of TRUST and 15 O-PET whole-brain OEF measurements were 1.79 ± 0.67% and 2.06 ± 1.55%, respectively, showing no difference between the two modalities (N = 10, P = .64). Further analyses on the effect of hematocrit revealed that correlation between PET OEF and TRUST OEF with assumed hematocrit remained significant (ICC = 0.8, P
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validation of t2 based Oxygen Extraction Fraction measurement with 15o positron emission tomography
Magnetic Resonance in Medicine, 2020Co-Authors: Dengrong Jiang, Shengwen Deng, Crystal Franklin, Wei Zhang, Betty L. Heyl, Paul A Jerabek, Michael Oboyle, Hanzhang LuAbstract:PURPOSE To evaluate the accuracy of T2 -based whole-brain Oxygen Extraction Fraction (OEF) estimation by comparing it with gold standard 15 O-PET measurements. METHODS Sixteen healthy adult subjects underwent MRI and 15 O-PET OEF measurements on the same day. On MRI, whole-brain OEF was quantified by T2 -relaxation-under-spin-tagging (TRUST) MRI, based on subject-specific hematocrit. The TRUST OEF was compared to the whole-brain averaged OEF produced by 15 O-PET. Agreement between TRUST and 15 O-PET whole-brain OEF measurements was examined in terms of intraclass correlation coefficient (ICC) and in absolute OEF values. In a subset of 10 subjects, test-retest reproducibility of whole-brain OEF was also evaluated and compared between the two modalities. RESULTS Across the 16 subjects, the mean whole-brain OEF of TRUST and 15 O-PET were 36.44 ± 4.07% and 36.45 ± 3.65%, respectively, showing no difference between the two modalities (P = .99). TRUST whole-brain OEF strongly correlated with that of 15 O-PET (N = 16, ICC = 0.90, P = 4 × 10-7 ). The coefficient-of-variation of TRUST and 15 O-PET whole-brain OEF measurements were 1.79 ± 0.67% and 2.06 ± 1.55%, respectively, showing no difference between the two modalities (N = 10, P = .64). Further analyses on the effect of hematocrit revealed that correlation between PET OEF and TRUST OEF with assumed hematocrit remained significant (ICC = 0.8, P < 2 × 10-5 ). CONCLUSION Whole-brain OEF measured by TRUST was in excellent agreement with gold standard 15 O-PET, with highly comparable accuracy and reproducibility. These findings suggest that TRUST MRI can provide accurate quantification of whole-brain OEF noninvasively.
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normal variations in brain Oxygen Extraction Fraction are partly attributed to differences in end tidal co2
Journal of Cerebral Blood Flow and Metabolism, 2020Co-Authors: Dengrong Jiang, Cuimei Xu, Kaisha Hazel, George Pottanat, Sevil Yasar, Paul B Rosenberg, Marilyn Albert, Hanzhang LuAbstract:Cerebral Oxygen Extraction Fraction is an important physiological index of the brain’s Oxygen consumption and supply and has been suggested to be a potential biomarker for a number of diseases such...
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elevated global cerebral blood flow Oxygen Extraction Fraction and unchanged metabolic rate of Oxygen in young adults with end stage renal disease an mri study
European Radiology, 2016Co-Authors: Hanzhang Lu, Gang Zheng, Xue Li, Zhe Zhang, Huijuan Chen, Xiang Kong, Xiaolu Jiang, Zongjun Zhang, Long Jiang ZhangAbstract:Objectives To noninvasively assess global cerebral blood flow (CBF), Oxygen Extraction Fraction (OEF) and cerebral metabolic rate of Oxygen (CMRO2) in young adults with end-stage renal disease (ESRD).
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non invasive imaging of Oxygen Extraction Fraction in adults with sickle cell anaemia
Brain, 2016Co-Authors: Lori C Jordan, Melissa C Gindville, Allison O Scott, Meher R Juttukonda, Megan K Strother, Adetola A Kassim, Sheauchiann Chen, Hanzhang Lu, Sumit Pruthi, Yu ShyrAbstract:Sickle cell anaemia is a monogenetic disorder with a high incidence of stroke. While stroke screening procedures exist for children with sickle cell anaemia, no accepted screening procedures exist for assessing stroke risk in adults. The purpose of this study is to use novel magnetic resonance imaging methods to evaluate physiological relationships between Oxygen Extraction Fraction, cerebral blood flow, and clinical markers of cerebrovascular impairment in adults with sickle cell anaemia. The specific goal is to determine to what extent elevated Oxygen Extraction Fraction may be uniquely present in patients with higher levels of clinical impairment and therefore may represent a candidate biomarker of stroke risk. Neurological evaluation, structural imaging, and the non-invasive T2-relaxation-under-spin-tagging magnetic resonance imaging method were applied in sickle cell anaemia ( n = 34) and healthy race-matched control ( n = 11) volunteers without sickle cell trait to assess whole-brain Oxygen Extraction Fraction, cerebral blood flow, degree of vasculopathy, severity of anaemia, and presence of prior infarct; findings were interpreted in the context of physiological models. Cerebral blood flow and Oxygen Extraction Fraction were elevated ( P < 0.05) in participants with sickle cell anaemia ( n = 27) not receiving monthly blood transfusions (interquartile range cerebral blood flow = 46.2–56.8 ml/100 g/min; Oxygen Extraction Fraction = 0.39–0.50) relative to controls (interquartile range cerebral blood flow = 40.8–46.3 ml/100 g/min; Oxygen Extraction Fraction = 0.33–0.38). Oxygen Extraction Fraction ( P < 0.0001) but not cerebral blood flow was increased in participants with higher levels of clinical impairment. These data provide support for T2-relaxation-under-spin-tagging being able to quickly and non-invasively detect elevated Oxygen Extraction Fraction in individuals with sickle cell anaemia with higher levels of clinical impairment. Our results support the premise that magnetic resonance imaging-based assessment of elevated Oxygen Extraction Fraction might be a viable screening tool for evaluating stroke risk in adults with sickle cell anaemia. * Abbreviations : CBF/V : cerebral blood flow/volume CMRO2 : cerebral metabolic rate of Oxygen consumption OEF : Oxygen Extraction Fraction SCA : sickle cell anaemia TRUST : T2-relaxation-under-spin-tagging
Yi Wang - One of the best experts on this subject based on the ideXlab platform.
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quantification of brain Oxygen Extraction Fraction using qsm and a hyperoxic challenge
Magnetic Resonance in Medicine, 2020Co-Authors: Erin L Mazerolle, Yi Wang, Bruce G PikeAbstract:PURPOSE To use hyperoxia in combination with QSM to quantify microvascular Oxygen Extraction Fraction (OEF) and cerebral metabolic rate of Oxygen (CMRO2 ) in healthy subjects and to cross-validate results with those from hypercapnia QSM-OEF. METHODS Ten healthy subjects were scanned on a 3T MRI scanner. At baseline normoxia and during hyperoxia (PetO2 = +300 mmHg), QSM data were acquired using a multi-echo gradient-echo (GRE) sequence, and cerebral blood flow data were acquired using a pseudocontinuous arterial spin labeling sequence. The OEF and CMRO2 maps were computed and compared with those from hypercapnia QSM-OEF, acquired in the same subjects, using correlation and Bland-Altman analysis in 16 vascular territories. RESULTS Hyperoxia QSM-OEF produced physiologically reasonable OEF and CMRO2 values in all subjects (gray-matter region of interest average OEF = 0.42 ± 0.04, average CMRO2 = 181 ± 34 μmol O2 /min/100 g). When compared with hypercapnia QSM-OEF, Bland-Altman plots revealed small deviations (mean OEF difference = 0.015, mean CMRO2 difference = 4.9 μmol O2 /min/100 g, P < .05). Good and excellent correlations of regional OEF and CMRO2 were found for the two methods. In addition, hyperoxia had minimal impact on cerebral blood flow (average gray-matter cerebral blood flow was reduced by 7.5 ± 5.4%). CONCLUSIONS Hyperoxia in combination with QSM is a robust approach to measure OEF. Compared with hypercapnia, hyperoxia is more comfortable and has minimal impact on cerebral blood flow.
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cluster analysis of time evolution cat for quantitative susceptibility mapping qsm and quantitative blood Oxygen level dependent magnitude qbold based Oxygen Extraction Fraction oef and cerebral metabolic rate of Oxygen cmro2 mapping
Magnetic Resonance in Medicine, 2020Co-Authors: Shun Zhang, Ajay Gupta, Simon Hubertus, Pascal Spincemaille, Thanh D Nguyen, Yi WangAbstract:PURPOSE: To improve the accuracy of QSM plus quantitative blood Oxygen level-dependent magnitude (QSM + qBOLD or QQ)-based mapping of the Oxygen Extraction Fraction (OEF) and cerebral metabolic rate of Oxygen (CMRO2 ) using cluster analysis of time evolution (CAT). METHODS: 3D multi-echo gradient echo and arterial spin labeling images were acquired in 11 healthy subjects and 5 ischemic stroke patients. DWI was also carried out on patients. CAT was developed for analyzing signal evolution over TE. QQ-based OEF and CMRO2 were reconstructed with and without CAT, and results were compared using region of interest analysis and a paired t-test. RESULTS: Simulations demonstrated that CAT substantially reduced noise error in QQ-based OEF. In healthy subjects, QQ-based OEF appeared less noisy and more uniform with CAT than without CAT; average OEF with and without CAT in cortical gray matter was 32.7 ± 4.0% and 37.9 ± 4.5%, with corresponding CMRO2 of 148.4 ± 23.8 and 171.4 ± 22.4 μmol/100 g/min, respectively. In patients, regions of low OEF were confined within the ischemic lesions defined on DWI when using CAT, which was not observed without CAT. CONCLUSION: The cluster analysis of time evolution (CAT) significantly improves the robustness of QQ-based OEF against noise.
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evaluation of Oxygen Extraction Fraction in systemic lupus erythematosus patients using quantitative susceptibility mapping
Journal of Cerebral Blood Flow and Metabolism, 2019Co-Authors: Mari Miyata, Yi Wang, Kohsuke Kudo, Shingo Kakeda, Shigeru Iwata, Yoshiya Tanaka, Yukunori KorogiAbstract:The purposes of this study are to assess the Oxygen Extraction Fraction (OEF) changes on MRI-based quantitative susceptibility mapping (QSM) in systemic lupus erythematosus (SLE) patients and to de...
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Using an artificial neural network for fast mapping of the Oxygen Extraction Fraction with combined QSM and quantitative BOLD.
Magnetic Resonance in Medicine, 2019Co-Authors: Simon Hubertus, Yi Wang, Sebastian Thomas, Shun Zhang, Lothar R SchadAbstract:PURPOSE: To apply an artificial neural network (ANN) for fast and robust quantification of the Oxygen Extraction Fraction (OEF) from a combined QSM and quantitative BOLD analysis of gradient echo data and to compare the ANN to a traditional quasi-Newton (QN) method for numerical optimization. METHODS: Random combinations of OEF, deOxygenated blood volume ( ν ), R2 , and nonblood magnetic susceptibility ( χnb ) with each parameter following a Gaussian distribution that represented physiological gray matter and white matter values were used to simulate quantitative BOLD signals and QSM values. An ANN was trained with the simulated data with added Gaussian noise. The ANN was applied to multigradient echo brain data of 7 healthy subjects, and the reconstructed parameters and maps were compared to QN results using Student t test and Bland-Altman analysis. RESULTS: Intersubject means and SDs of gray matter were OEF =43.5±0.8 %, R2=13.5±0.3 Hz, ν=3.4±0.1 %, χnb=-25±5 ppb for ANN; and OEF = 43.8±5.2 %, R2=12.2±0.8 Hz, ν=4.2±0.6 %, χnb=-39±7 ppb for QN, with a significant difference ( P
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using an artificial neural network for fast mapping of the Oxygen Extraction Fraction with combined qsm and quantitative bold
Magnetic Resonance in Medicine, 2019Co-Authors: Simon Hubertus, Yi Wang, Sebastian Thomas, Shun Zhang, Lothar R SchadAbstract:PURPOSE To apply an artificial neural network (ANN) for fast and robust quantification of the Oxygen Extraction Fraction (OEF) from a combined QSM and quantitative BOLD analysis of gradient echo data and to compare the ANN to a traditional quasi-Newton (QN) method for numerical optimization. METHODS Random combinations of OEF, deOxygenated blood volume ( ν ), R2 , and nonblood magnetic susceptibility ( χnb ) with each parameter following a Gaussian distribution that represented physiological gray matter and white matter values were used to simulate quantitative BOLD signals and QSM values. An ANN was trained with the simulated data with added Gaussian noise. The ANN was applied to multigradient echo brain data of 7 healthy subjects, and the reconstructed parameters and maps were compared to QN results using Student t test and Bland-Altman analysis. RESULTS Intersubject means and SDs of gray matter were OEF =43.5±0.8 %, R2=13.5±0.3 Hz, ν=3.4±0.1 %, χnb=-25±5 ppb for ANN; and OEF = 43.8±5.2 %, R2=12.2±0.8 Hz, ν=4.2±0.6 %, χnb=-39±7 ppb for QN, with a significant difference ( P<0.05 ) for R2 , ν , and χnb . For white matter, they were OEF = 47.5±1.1 %, R2=17.1±0.4 Hz, ν=2.5±0.2 %, χnb=-38±5 ppb for ANN; and OEF =42.3±5.6 %, R2=16.7±0.7 Hz, ν=2.9±0.3 %, χnb=-45±9 ppb for QN, with a significant difference ( P<0.05 ) for OEF and ν . ANN revealed more gray-white matter contrast but less intersubject variation in OEF than QN. In contrast to QN, the ANN reconstruction did not need an additional sequence for parameter initialization and took approximately 1 s rather than roughly 1 h. CONCLUSION ANNs allow faster and, with regard to initialization, more robust reconstruction of OEF maps with lower intersubject variation than QN approaches.
