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Dendy JM, Hughes SG, Soslow JH, Clark DE, Paschal CB, Gore JC. Myocardial Tissue Oxygenation and Microvascular Blood Volume Measurement Using a Contrast Blood Oxygenation Level-Dependent Imaging Model. Invest Radiol 2022; 57:561-566. [PMID: 35438656 PMCID: PMC9355912 DOI: 10.1097/rli.0000000000000871] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES We propose a method of quantitatively measuring drug-induced microvascular volume changes, as well as drug-induced changes in blood oxygenation using calibrated blood oxygen level-dependent magnetic resonance imaging (MRI). We postulate that for MRI signals there is a contribution to R2* relaxation rates from static susceptibility effects of the intravascular blood that scales with the blood volume/magnetic field and depends on the oxygenation state of the blood. These may be compared with the effects of an intravascular contrast agent. With 4 R2* measurements, microvascular blood volume (MBV) and tissue oxygenation changes can be quantified with the administration of a vasoactive drug. MATERIALS AND METHODS The protocol examined 12 healthy rats in a prospective observational study. R2* maps were acquired with and without infusion of adenosine, which increases microvascular blood flow, or dobutamine, which increases myocardial oxygen consumption. In addition, R2* maps were acquired after the intravenous administration of a monocrystalline iron oxide nanoparticle, with and without adenosine or dobutamine. RESULTS Total microvascular volume was shown to increase by 10.8% with adenosine and by 25.6% with dobutamine ( P < 0.05). When comparing endocardium versus epicardium, both adenosine and dobutamine demonstrated significant differences between endocardial and epicardial MBV changes ( P < 0.05). Total myocardial oxygenation saturation increased by 6.59% with adenosine and by 1.64% with dobutamine ( P = 0.27). The difference between epicardial and endocardial oxygenation changes were significant with each drug (adenosine P < 0.05, dobutamine P < 0.05). CONCLUSIONS Our results demonstrate the ability to quantify microvascular volume and oxygenation changes using calibrated blood oxygen level-dependent MRI, and we demonstrate different responses of adenosine and dobutamine. This method has clinical potential in examining microvascular disease in various disease states without the administration of radiopharmaceuticals or gadolinium-based contrast agents.
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Affiliation(s)
- Jeffrey M Dendy
- From the Division of Cardiovascular Medicine, Department of Internal Medicine, Vanderbilt University Medical Center
| | - Sean G Hughes
- From the Division of Cardiovascular Medicine, Department of Internal Medicine, Vanderbilt University Medical Center
| | - Jonathan H Soslow
- Thomas P. Graham Division of Pediatric Cardiology, Department of Pediatrics, Monroe Carell Jr. Children's Hospital at Vanderbilt
| | - Daniel E Clark
- From the Division of Cardiovascular Medicine, Department of Internal Medicine, Vanderbilt University Medical Center
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Rotkopf LT, Buschle LR, Schlemmer HP, Ziener CH. Influence of diffusion on transverse relaxation rates and phases of an ensemble of magnetic spheres. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2022; 341:107259. [PMID: 35779309 DOI: 10.1016/j.jmr.2022.107259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Revised: 05/30/2022] [Accepted: 06/19/2022] [Indexed: 06/15/2023]
Abstract
In quantitative susceptibility mapping, the tissue susceptibility is determined from the magnitude and phase of the gradient echo signal, which is influenced by the interplay of complex susceptibility and diffusion effect. Herein, we analytically analyze the influence of diffusion on magnitude and phase images generated by randomly arranged magnetic spheres as a model of intracerebral iron depositions. We demonstrate that both gradient and spin echo relaxation rate constants have a strong and nonlinear dependence on diffusion strength and give empirical formulas for magnitude and phase. This may be used in the future to improve QSM processing methods. In addition, we show that, in theory, combined acquisitions of gradient and spin echo can be used to determine the dimension of the magnetic spheres and the diffusion strength.
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Affiliation(s)
- L T Rotkopf
- Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 220, 69120 Heidelberg, Germany; Medical Faculty, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
| | - L R Buschle
- Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 220, 69120 Heidelberg, Germany
| | - H-P Schlemmer
- Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 220, 69120 Heidelberg, Germany
| | - C H Ziener
- Department of Radiology, German Cancer Research Center, Im Neuenheimer Feld 220, 69120 Heidelberg, Germany.
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3
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Fischer K, Guensch DP, Jung B, King I, von Tengg-Kobligk H, Giannetti N, Eberle B, Friedrich MG. Insights Into Myocardial Oxygenation and Cardiovascular Magnetic Resonance Tissue Biomarkers in Heart Failure With Preserved Ejection Fraction. Circ Heart Fail 2022; 15:e008903. [PMID: 35038887 DOI: 10.1161/circheartfailure.121.008903] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND The pathophysiology of heart failure with preserved ejection fraction is not well understood, but evidence strongly suggests involvement of microvascular dysfunction. We studied the myocardial oxygenation reserve as a direct marker of coronary vascular function and its relation to myocardial deformation and tissue characteristics by cardiovascular magnetic resonance (CMR). METHODS In a dual-center case-control study, patients with heart failure and preserved ejection fraction (>50%) and healthy controls older than 50 years underwent quantitative CMR for ventricular volumes and functional assessment with feature tracking, as well as tissue characterization (T1, T2, extracellular volume). Coronary vascular function was measured by oxygenation-sensitive (OS)-CMR of the myocardial oxygenation response to a vasoactive breathing maneuver. RESULTS Twenty-nine patients completed the CMR exam. Compared with cutoffs derived from 12 control subjects, circumferential peak strain was attenuated in 97% of patients. Native T1 was elevated in 93%, extracellular volume was elevated in 83%. Sixty-six percent of patients revealed either regional or global myocardial edema, defined by an increased myocardial T2. An attenuated global myocardial oxygenation reserve (<4.4%) was observed in 96% of the patients (1.7±3.9% versus 9.1±5.3% in controls, P<0.001). This was correlated with septal wall thickness (r=-0.54, P=0.003), edema (myocardial T2; β=-0.26% oxygenation-sensitive/ms [95% CI, -0.49 to -0.03], P=0.029), and reduced diastolic strain rate (β=1.50% oxygenation-sensitive/s-1 [95% CI, 0.06-2.90], P=0.042). CONCLUSIONS In patients with clinical heart failure with preserved ejection fraction, vascular dysfunction as measured by an attenuated myocardial oxygenation reserve is associated with myocardial edema, a thicker septum, and diastolic dysfunction. A quantitative comprehensive CMR exam including oxygenation-sensitive-CMR allows for comprehensive imaging-based phenotyping of heart failure with preserved ejection fraction.
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Affiliation(s)
- Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Switzerland. (K.F., D.P.G., I.K., B.E.).,Research Institute of the McGill University Health Centre, Montreal, QB, Canada (K.F.)
| | - Dominik P Guensch
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Switzerland. (K.F., D.P.G., I.K., B.E.).,Department of Diagnostic, Interventional' and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Switzerland. (D.P.G., B.J., H.v.T.-K.)
| | - Bernd Jung
- Department of Diagnostic, Interventional' and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Switzerland. (D.P.G., B.J., H.v.T.-K.)
| | - Iman King
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Switzerland. (K.F., D.P.G., I.K., B.E.)
| | - Hendrik von Tengg-Kobligk
- Department of Diagnostic, Interventional' and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Switzerland. (D.P.G., B.J., H.v.T.-K.)
| | - Nadia Giannetti
- Departments of Medicine and Diagnostic Radiology, McGill University Health Centre, Montreal, QB, Canada (N.G., M.G.F.)
| | - Balthasar Eberle
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Switzerland. (K.F., D.P.G., I.K., B.E.)
| | - Matthias G Friedrich
- Departments of Medicine and Diagnostic Radiology, McGill University Health Centre, Montreal, QB, Canada (N.G., M.G.F.).,Department of Family Medicine, McGill University, Montreal, QB, Canada (M.G.F.).,Departments of Cardiac Sciences and Radiology, University of Calgary, AB, Canada (M.G.F.)
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4
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Emmerich J, Bachert P, Ladd ME, Straub S. On the separation of susceptibility sources in quantitative susceptibility mapping: Theory and phantom validation with an in vivo application to multiple sclerosis lesions of different age. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 330:107033. [PMID: 34303117 DOI: 10.1016/j.jmr.2021.107033] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 06/14/2021] [Accepted: 07/08/2021] [Indexed: 06/13/2023]
Abstract
PURPOSE In biological tissue, phase contrast is determined by multiple substances such as iron, myelin or calcifications. Often, these substances occur co-located within the same measurement volume. However, quantitative susceptibility mapping can solely measure the average susceptibility per voxel. To provide new insight in disease progression and mechanisms in neurological diseases, where multiple processes such as demyelination and iron accumulation occur simultaneously in the same location, a separation of susceptibility sources is desirable to disentangle the underlying susceptibility proportions. METHODS The basic concept of separating the susceptibility effects from sources with different sign within one voxel is to include information on relaxation rate ΔR2∗ in the quantitative susceptibility mapping reconstruction pipeline. The presented reconstruction algorithm is implemented as a constrained minimization problem and solved using conjugate gradients. The algorithm is evaluated using a software phantom and validated in MRI measurements with a phantom containing mixtures of microscopic positive and negative susceptibility sources. Data from three multiple sclerosis patients are used to show in vivo feasibility. RESULTS In numerical simulations, the feasibility of disentangling susceptibility sources within the same voxel was confirmed provided the critera of the static dephasing regime were fulfilled. In phantom experiments, the magnitude decay kernel, which is an essential reconstruction parameter of the algorithm, was determined to be Dm=194.5T-1s-1ppm-1, and susceptibility sources could be separated in MRI measurement data. CONCLUSIONS In conclusion, in this study a detailed description of the implementation of an algorithm for the separation of positive and negative susceptibility sources within the same volume element as well as its limitations is presented and validated quantitatively in both simulation and phantom experiments for the first time. An application to multiple sclerosis lesions shows promising results for in vivo usability.
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Affiliation(s)
- Julian Emmerich
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Peter Bachert
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Mark E Ladd
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany; Faculty of Medicine, Heidelberg University, Heidelberg, Germany
| | - Sina Straub
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
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5
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Hillier E, Friedrich MG. The Potential of Oxygenation-Sensitive CMR in Heart Failure. Curr Heart Fail Rep 2021; 18:304-314. [PMID: 34378154 DOI: 10.1007/s11897-021-00525-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 06/05/2021] [Indexed: 12/24/2022]
Abstract
PURPOSE OF REVIEW Cardiac magnetic resonance imaging (CMR) use in the context of heart failure (HF) has increased over the last decade as it is able to provide detailed, quantitative information on function, morphology, and myocardial tissue composition. Furthermore, oxygenation-sensitive CMR (OS-CMR) has emerged as a CMR imaging method capable of monitoring changes of myocardial oxygenation without the use of exogenous contrast agents. RECENT FINDINGS The contributions of OS-CMR to the investigation of patients with HF includes not only a fully quantitative assessment of cardiac morphology, function, and tissue characteristics, but also high-resolution information on both endothelium-dependent and endothelium-independent vascular function as assessed through changes of myocardial oxygenation. In patients with heart failure, OS-CMR can provide deep phenotyping on the status and important associated pathophysiology as a one-stop, needle-free diagnostic imaging test.
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Affiliation(s)
- Elizabeth Hillier
- Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada.,Faculty of Medicine and Dentistry, University of Alberta, Edmonton, AB, Canada
| | - Matthias G Friedrich
- Faculty of Medicine and Health Sciences, McGill University, Montreal, QC, Canada. .,Departments of Medicine and Diagnostic Radiology, McGill University, 1001 Decarie Blvd, Montreal, QC, H4A 3J1, Canada.
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6
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Emmerich J, Bachert P, Ladd ME, Straub S. A novel phantom with dia- and paramagnetic substructure for quantitative susceptibility mapping and relaxometry. Phys Med 2021; 88:278-284. [PMID: 34332237 DOI: 10.1016/j.ejmp.2021.07.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 06/22/2021] [Accepted: 07/12/2021] [Indexed: 12/20/2022] Open
Abstract
PURPOSE A phantom is presented in this study that allows for an experimental evaluation of QSM reconstruction algorithms. The phantom contains susceptibility producing particles with dia- and paramagnetic properties embedded in an MRI visible medium and is suitable to assess the performance of algorithms that attempt to separate isotropic dia- and paramagnetic susceptibility at the sub-voxel level. METHODS The phantom was built from calcium carbonate (diamagnetic) and tungsten carbide particles (paramagnetic) embedded in gelatin and surrounded by agarose gel. Different mass fractions and mixing ratios of both susceptibility sources were used. Gradient echo data were acquired at 1.5 T, 3 T and 7 T. Susceptibility maps were calculated using the MEDI toolbox and relaxation rates ΔR2∗ were determined using exponential fitting. RESULTS Relaxation rates as well as susceptibility values generally coincide with the theoretical values for particles fulfilling the assumptions of the the static dephasing regime with stronger deviations for relaxation rates at higher field strength and for high susceptibility values. MRI raw data are available for free academic use as supplementary material. CONCLUSIONS In this study, a susceptibility phantom is presented that might find its application in the development and quantitative validation of current and future QSM reconstruction algorithms which aim to separate the influence of isotropic dia- and paramagnetic substructure in quantitative susceptibility mapping.
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Affiliation(s)
- Julian Emmerich
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Peter Bachert
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany
| | - Mark E Ladd
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Faculty of Physics and Astronomy, Heidelberg University, Heidelberg, Germany; Faculty of Medicine, Heidelberg University, Heidelberg, Germany
| | - Sina Straub
- Division of Medical Physics in Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.
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Zhang J, Chen J, Chen Q, Chen J, Luo K, Pan L, Zhang Y, Dou W, Xing W. Can R 2 ' mapping evaluate hypoxia in renal ischemia reperfusion injury quantitatively? An experimental study. Magn Reson Med 2021; 86:974-983. [PMID: 33724527 DOI: 10.1002/mrm.28696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 12/31/2020] [Accepted: 01/04/2021] [Indexed: 11/09/2022]
Abstract
PURPOSE To explore if R2 ' mapping can assess renal hypoxia in rabbits with ischemia reperfusion injury (IRI). METHODS Forty rabbits were randomly divided into 4 groups according to the clipping time: the sham group and 45 min, 60 min, and 75 min for the mild, moderate, and severe groups (with n = 10 each group), respectively. Intravenous furosemide (FU) was administered 24 h after IRI. All rabbits were performed 5 times (IRIpre , IRI24h , FU5min , FU12min , and FU24min ) with a 3.0 Tesla MR. The R2 ' values and the hypoxic scores were then recorded. The repeated measurement analysis of variance and Spearman correlation analysis was used for statistical analysis. RESULTS Compared to the baseline, the medullary R2 ' values increased significantly 24 h after the IRI (baseline 19.31 ± 1.21 s-1 , mild group 20.05 ± 1.26 s-1 , moderate group 25.38 ± 1.38 s-1 , and severe group 25.79 ± 1.10 s-1 ; each P < .001). FU led to a significant decrease in the medullary R2 ' value (sham group 11.17 ± 4.33 s-1 , mild group 7.80 ± 0.74 s-1 , moderate group 3.92 ± 0.28 s-1 , and severe group 3.82 ± 0.23 s-1 ; each P < .05). Quantitative hypoxic scores revealed significant differences among the 4 groups in the outer medulla (P < .001 each). The medullary R2 ' differences (before and after intravenous FU) were significantly correlated with the hypoxic scores, respectively (P < .001). CONCLUSION R2 ' mapping can evaluate the renal hypoxia in the procession of IRI in rabbits and might serve as a quantitative biomarker for IRI.
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Affiliation(s)
- Jinggang Zhang
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Jie Chen
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Qin Chen
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Jing Chen
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Kai Luo
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Liang Pan
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Yongcheng Zhang
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
| | - Weiqiang Dou
- MR research China, GE Healthcare, Beijing, People's Republic of China
| | - Wei Xing
- Department of Radiology, Third Affiliated Hospital of Soochow University, Changzhou, People's Republic of China
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Jiang Z, Wang Y, Ding J, Yu S, Zhang J, Zhou H, Di J, Xing W. Susceptibility weighted imaging (SWI) for evaluating renal dysfunction in type 2 diabetes mellitus: a preliminary study using SWI parameters and SWI-based texture features. ANNALS OF TRANSLATIONAL MEDICINE 2021; 8:1673. [PMID: 33490185 PMCID: PMC7812222 DOI: 10.21037/atm-20-7121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Background Susceptibility weighted imaging (SWI) could reflect tissue blood oxygen levels, and then whether it could be used to evaluate renal injury remains to be further studied. This study aimed to examine the performance of SWI parameters and SWI-based texture features in evaluating renal dysfunction of type 2 diabetes mellitus (T2DM). Methods Forty-five patients with T2DM were included. With the estimated glomerular filtration rate (eGFR), the patients were divided into non-moderate-severe renal injured group (non-msRI, eGFR >60 mL/min/1.73 m2) and moderate-severe renal injured group (msRI, eGFR ≤60 mL/min/1.73 m2). The 3 SWI parameters and 16 SWI-based texture features between non-msRI and msRI were compared. The correlation between the parameters and BUN, Scr was analyzed. Results The signal intensity ratio of the medulla to psoas muscle (MPswi) was significantly lower than the signal intensity ratio of the cortex to psoas muscle (CPswi) in non-msRI and msRI group (t=8.619, 3.483, respectively, P<0.05). MPswi was higher, and the signal intensity ratio of the cortex to the medulla (CMswi), Skewness, Correlation were lower in msRI than in non-msRI (P<0.05). These parameters showed similar diagnostic efficacies for msRI (P>0.05), and AUCs were 0.703–0.854. CMswi was an independent protective factor for msRI (OR =0.026, P=0.003). MPswi and CMswi were correlated with BUN (r=0.416, −0.545, P<0.05). CMswi and Correlation were correlated with Scr (r=−0.645, −0.411, P<0.05). Conclusions SWI was valuable for assessing renal dysfunction, which may be helpful for the evaluation of moderate-severe renal injured patients with T2DM.
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Affiliation(s)
- Zhenxing Jiang
- Department of Radiology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Yu Wang
- Department of Radiology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Jiule Ding
- Department of Radiology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Shengnan Yu
- Department of Radiology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Jinggang Zhang
- Department of Radiology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Hua Zhou
- Department of Nephrology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Jia Di
- Department of Nephrology, The Third Affiliated Hospital of Soochow University, Changzhou, China
| | - Wei Xing
- Department of Radiology, The Third Affiliated Hospital of Soochow University, Changzhou, China
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On the influence of two coexisting species of susceptibility-producing structures on the R2∗ relaxation rate. Magn Reson Imaging 2020; 71:170-177. [DOI: 10.1016/j.mri.2020.06.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 05/06/2020] [Accepted: 06/09/2020] [Indexed: 01/01/2023]
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10
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Dependence of the frequency distribution around a vessel on the voxel orientation. Magn Reson Imaging 2019; 57:259-270. [DOI: 10.1016/j.mri.2018.09.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 09/10/2018] [Accepted: 09/13/2018] [Indexed: 12/31/2022]
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Buschle LR, Kurz FT, Kampf T, Schlemmer HP, Ziener CH. Spin dephasing around randomly distributed vessels. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 299:12-20. [PMID: 30529850 DOI: 10.1016/j.jmr.2018.11.014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 11/27/2018] [Accepted: 11/28/2018] [Indexed: 06/09/2023]
Abstract
We analyze the gradient echo signal in the presence of blood vessel networks. Both, diffusion and susceptibility effects are analytically emphasized within the Bloch-Torrey equation. Solving this equation, we present the first exact description of the local magnetization around a single vessel. This allows us to deduce the gradient echo signal of parallel vessels randomly distributed in a plane, which is valid for arbitrary mean vessel diameters in the range of physiological relevant blood volume fractions. Thus, the results are potentially relevant for gradient echo measurements of blood vessel networks with arbitrary vessel size.
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Affiliation(s)
- L R Buschle
- German Cancer Research Center - DKFZ, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany; Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany; Heidelberg University, Faculty of Physics and Astronomy, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany
| | - F T Kurz
- German Cancer Research Center - DKFZ, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany; Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany
| | - T Kampf
- University of Würzburg, Department of Experimental Physics 5, Am Hubland, 97074 Würzburg, Germany; Würzburg University Hospital, Department of Neuroradiology, Josef-Schneider-Straße 11, 97080 Würzburg, Germany
| | - H P Schlemmer
- German Cancer Research Center - DKFZ, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
| | - C H Ziener
- German Cancer Research Center - DKFZ, Im Neuenheimer Feld 280, 69120 Heidelberg, Germany; Heidelberg University Hospital, Im Neuenheimer Feld 400, 69120 Heidelberg, Germany.
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12
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Guensch DP, Fischer K, Jung C, Hurni S, Winkler BM, Jung B, Vogt AP, Eberle B. Relationship between myocardial oxygenation and blood pressure: Experimental validation using oxygenation-sensitive cardiovascular magnetic resonance. PLoS One 2019; 14:e0210098. [PMID: 30650118 PMCID: PMC6334913 DOI: 10.1371/journal.pone.0210098] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Accepted: 12/16/2018] [Indexed: 12/14/2022] Open
Abstract
Background The relationship between mean arterial pressure (MAP) and coronary blood flow is well described. There is autoregulation within a MAP range of 60 to 140 mmHg providing near constant coronary blood flow. Outside these limits flow becomes pressure-dependent. So far, response of myocardial oxygenation to changes in pressure and flow has been more difficult to assess. While established techniques mostly require invasive approaches, Oxygenation-Sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a technique that can non-invasively assess changes in myocardial tissue oxygenation. The purpose of this study was to follow myocardial oxygenation over a wide range of blood pressure variation within and outside known coronary autoregulatory limits using OS-CMR, and to relate these data to coronary hemodynamics. Methods Ten anaesthetized swine (German Large White) underwent left-sided thoracotomy and attachment of a perivascular flow probe to the proximal left anterior descending (LAD) coronary artery for continuous measurement of blood flow (QLAD). Thereafter, animals were transferred into a 3T MRI scanner. Mean arterial pressure (MAP) was varied in 10–15 mmHg steps by administering alpha1-receptor agents phenylephrine or urapidil. For each MAP level, OS-CMR images as well as arterial and coronary sinus blood gas samples were obtained simultaneously during brief periods of apnea. Relative changes (Δ) of coronary sinus oxygen saturation (ScsO2), oxygen delivery (DO2) and demand (MVO2), extraction ratio (O2ER) and excess (Ω) from respective reference levels at a MAP of 70 mmHg were determined and were compared to %change in OS-signal intensity (OS-SI) in simultaneously acquired OS-CMR images. Results QLAD response indicated autoregulation between MAP levels of 52 mmHg (lower limit) and127 mmHg (upper limit). OS-CMR revealed a global myocardial oxygenation deficit occurring below the lower autoregulation limit, with the nadir of OS-SI at -9.0%. With MAP values surpassing 70 mmHg, relative OS-SI increased to a maximum of +10.6%. Consistent with this, ΔScsO2, ΔDO2, ΔMVO2, ΔO2ER and ΔΩ responses indicated increasing mismatch of oxygenation balance outside the autoregulated zone. Changes in global OS-CMR were significantly correlated with all of these parameters (p≤0.02) except with ΔMVO2. Conclusion OS-CMR offers a novel and non-invasive route to evaluate the effects of blood pressure variations, as well as of cardiovascular drugs and interventions, on global and regional myocardial oxygenation, as demonstrated in a porcine model. OS-CMR identified mismatch of O2 supply and demand below the lower limit of coronary autoregulation. Vasopressor induced acute hypertension did not compromise myocardial oxygenation in healthy hearts despite increased cardiac workload and O2 demand. The clinical usefulness of OS-CMR remains to be established.
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Affiliation(s)
- Dominik P. Guensch
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- * E-mail:
| | - Kady Fischer
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
- McGill University Health Centre, Montreal, QC, Canada
| | - Christof Jung
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Samuel Hurni
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernhard M. Winkler
- Department of Cardiovascular Surgery, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Bernd Jung
- Institute for Diagnostic, Interventional and Paediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Andreas P. Vogt
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Balthasar Eberle
- Department of Anaesthesiology and Pain Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
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Vessel radius mapping in an extended model of transverse relaxation. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2018; 31:531-551. [DOI: 10.1007/s10334-018-0677-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Revised: 01/14/2018] [Accepted: 01/15/2018] [Indexed: 10/18/2022]
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14
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Vuong QL, Gillis P, Roch A, Gossuin Y. Magnetic resonance relaxation induced by superparamagnetic particles used as contrast agents in magnetic resonance imaging: a theoretical review. WILEY INTERDISCIPLINARY REVIEWS-NANOMEDICINE AND NANOBIOTECHNOLOGY 2017; 9. [PMID: 28398013 DOI: 10.1002/wnan.1468] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/2016] [Revised: 02/02/2017] [Accepted: 02/13/2017] [Indexed: 12/24/2022]
Abstract
Superparamagnetic nanoparticles are used as contrast agents in magnetic resonance imaging and allow, for example, the detection of tumors or the tracking of stem cells in vivo. By producing magnetic inhomogeneities, they influence the nuclear magnetic relaxation times, which results in a darkening, on the image, of the region containing these particles. A great number of studies have been devoted to their magnetic properties, to their synthesis and to their influence on nuclear magnetic relaxation. The theoretical and fundamental understanding of the behavior of these particles is a necessary step in predicting their efficiency as contrast agents, or to be able to experimentally obtain some of their properties from a nuclear magnetic resonance measurement. Many relaxation models have been published, and choosing one of them is not always easy, many parameters and conditions have to be taken into account. Relaxation induced by superparamagnetic particles is generally attributed to an outersphere relaxation mechanism. Each model can only be used under specific conditions (motional averaging regime, static regime, high magnetic field, etc.) or for a particular sequence (Carr-Purcell-Meiboom-Gill, spin echo, free-induction decay, nuclear magnetic relaxation dispersion profile, etc.). The parameters included in the equations must be carefully interpreted. In some more complex conditions, simulations are necessary to be able to predict the relaxation rates. A good agreement is usually observed between the theoretical predictions and the experimental results, although some data still cannot be fully understood, such as the dependence of the transverse relaxation on the magnetic field. WIREs Nanomed Nanobiotechnol 2017, 9:e1468. doi: 10.1002/wnan.1468 For further resources related to this article, please visit the WIREs website.
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Affiliation(s)
| | | | - Alain Roch
- Faculty of Medicine, UMONS, Mons, Belgium
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15
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Nagao M, Yamasaki Y, Kawanami S, Kamitani T, Sagiyama K, Higo T, Ide T, Takemura A, Ishizaki U, Fukushima K, Watanabe Y, Honda H. Quantification of myocardial oxygenation in heart failure using blood-oxygen-level-dependent T2* magnetic resonance imaging: Comparison with cardiopulmonary exercise test. Magn Reson Imaging 2017; 39:138-143. [PMID: 28216453 DOI: 10.1016/j.mri.2017.02.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 02/09/2017] [Accepted: 02/13/2017] [Indexed: 11/18/2022]
Abstract
PURPOSE Quantification of myocardial oxygenation (MO) in heart failure (HF) has been less than satisfactory. This has necessitated the use of invasive techniques to measure MO directly or to determine the oxygen demand during exercise using the cardiopulmonary exercise (CPX) test. We propose a new quantification method for MO using blood-oxygen-level-dependent (BOLD) myocardial T2* magnetic resonance imaging (M-T2* MRI), and investigate its correlation with CPX results. METHODS Thirty patients with refractory HF who underwent cardiac MRI and CPX test for heart transplantation, and 24 healthy, age-matched volunteers as controls were enrolled. M-T2* imaging was performed using a 3-Tesla and multi-echo gradient-echo sequence. M-T2* was calculated by fitting the signal intensity data for the mid-left ventricular septum to a decay curve. M-T2* was measured under room-air (T2*-air) and after inhalation of oxygen for 10min at a flow rate of 10L/min (T2*-oxy). MO was defined as the difference between the two values (ΔT2*). Changes in M-T2* at the two conditions and ΔT2* between the two groups were compared. Correlation between ΔT2* and CPX results was analyzed using the Pearson coefficient. RESULTS T2*-oxy was significantly greater than T2*-air in patients with HF (29.9±7.3ms vs. 26.7±6.0ms, p<0.001), whereas no such difference was observed in controls (25.5±4.0ms vs. 25.4±4.4ms). ΔT2* was significantly greater for patients with HF than for controls (3.2±4.5ms vs. -0.1±1.3ms, p<0.001). A significant correlation between ΔT2* and CPX results (peak VO2, r=-0.46, p<0.05; O2 pulse, r=-0.54, p<0.005) was observed. CONCLUSION ΔT2* is increased T2*-oxy is greater in patients with HF, and is correlated with oxygen metabolism during exercise as measured by the CPX test. Hence, ΔT2* can be used as a surrogate marker of MO instead of CPX test.
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Affiliation(s)
- Michinobu Nagao
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, Tokyo, Japan.
| | - Yuzo Yamasaki
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Satoshi Kawanami
- Molecular Imaging and Diagnosis, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Takeshi Kamitani
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Koji Sagiyama
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Taiki Higo
- Cardiovascular Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Tomomi Ide
- Cardiovascular Medicine, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Atsushi Takemura
- Department of Marketing Division, Philips Healthcare Japan, Tokyo, Japan
| | - Umiko Ishizaki
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, Tokyo, Japan
| | - Kenji Fukushima
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, Tokyo, Japan
| | - Yuji Watanabe
- Molecular Imaging and Diagnosis, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
| | - Hiroshi Honda
- Department of Clinical Radiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan
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Roubille F, Fischer K, Guensch DP, Tardif JC, Friedrich MG. Impact of hyperventilation and apnea on myocardial oxygenation in patients with obstructive sleep apnea – An oxygenation-sensitive CMR study. J Cardiol 2017; 69:489-494. [DOI: 10.1016/j.jjcc.2016.03.011] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Revised: 03/06/2016] [Accepted: 03/22/2016] [Indexed: 11/30/2022]
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Guensch DP, Nadeshalingam G, Fischer K, Stalder AF, Friedrich MG. The impact of hematocrit on oxygenation-sensitive cardiovascular magnetic resonance. J Cardiovasc Magn Reson 2016; 18:42. [PMID: 27435406 PMCID: PMC4952059 DOI: 10.1186/s12968-016-0262-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/28/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Oxygenation-sensitive (OS) Cardiovascular Magnetic Resonance (CMR) is a promising utility in the diagnosis of heart disease. Contrast in OS-CMR images is generated through deoxyhemoglobin in the tissue, which is negatively correlated with the signal intensity (SI). Thus, changing hematocrit levels may be a confounder in the interpretation of OS-CMR results. We hypothesized that hemodilution confounds the observed signal intensity in OS-CMR images. METHODS Venous and arterial blood from five pigs was diluted with lactated Ringer solution in 10 % increments to 50 %. The changes in signal intensity (SI) were compared to changes in blood gases and hemoglobin concentration. We performed an OS-CMR scan in 21 healthy volunteers using vasoactive breathing stimuli at baseline, which was then repeated after rapid infusion of 1 L of lactated Ringer's solution within 5-8 min. Changes of SI were measured and compared between the hydration states. RESULTS The % change in SI from baseline for arterial (r = -0.67, p < 0.0001) and venous blood (r = -0.55, p = 0.002) were negatively correlated with the changes in hemoglobin (Hb). SI changes in venous blood were also associated with SO2 (r = 0.68, p < 0.0001) and deoxyHb concentration (-0.65, p < 0.0001). In healthy volunteers, rapid infusion resulted in a significant drop in the hemoglobin concentration (142.5 ± 15.2 g/L vs. 128.8 ± 15.2 g/L; p < 0.0001). Baseline myocardial SI increased by 3.0 ± 5.7 % (p = 0.026) following rapid infusion, and in males there was a strong association between the change in hemoglobin concentration and % changes in SI (r = 0.82, p = 0.002). After hyperhydration, the SI response after hyperventilation was attenuated (HV, p = 0.037), as was the maximum SI increase during apnea (p = 0.012). The extent of SI attenuation was correlated with the reduction in hemoglobin concentration at the end of apnea (r = 0.55, p = 0.012) for all subjects and at maximal SI (r = 0.63, p = 0.037) and the end of breath-hold (r = 0.68, p = 0.016) for males only. CONCLUSION In dynamic studies using oxygenation-sensitive CMR, the hematocrit level affects baseline signal intensity and the observed signal intensity response. Thus, the hydration status of the patient may be a confounder for OS-CMR image analysis.
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Affiliation(s)
- Dominik P. Guensch
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
- />Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010 Bern, Switzerland
- />Instutite of Diagnostic, Interventional and Pediatric Radiology, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland
| | - Gobinath Nadeshalingam
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
| | - Kady Fischer
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
- />Department of Anesthesiology and Pain Therapy, Inselspital, Bern University Hospital, University of Bern, Freiburgstrasse, 3010 Bern, Switzerland
| | | | - Matthias G. Friedrich
- />Philippa & Marvin Carsley CMR Centre at the Montreal Heart Institute, Montreal, QC Canada
- />Department of Medicine, Heidelberg University, Heidelberg, Germany
- />Departments of Cardiac Sciences and Radiology, University of Calgary, Calgary, AB Canada
- />Department of Radiology, Université de Montréal, Montreal, QC Canada
- />Departments of Medicine and Radiology, McGill University Health Centre, Montreal, QC Canada
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Troprès I, Pannetier N, Grand S, Lemasson B, Moisan A, Péoc'h M, Rémy C, Barbier EL. Imaging the microvessel caliber and density: Principles and applications of microvascular MRI. Magn Reson Med 2014; 73:325-41. [DOI: 10.1002/mrm.25396] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Revised: 07/08/2014] [Accepted: 07/11/2014] [Indexed: 12/22/2022]
Affiliation(s)
- Irène Troprès
- IRMaGe; Université Grenoble Alpes; Grenoble France
- UMS 3552; CNRS; Grenoble France
- US 017; INSERM; Grenoble France
- IRMaGe, Hôpital Michallon; Centre Hospitalier Universitaire de Grenoble; Grenoble France
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France. INSERM; U836 Grenoble France
| | - Nicolas Pannetier
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France
- INSERM; U836 Grenoble France
| | - Sylvie Grand
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France
- INSERM; U836 Grenoble France
- CLUNI, Hôpital Michallon; Centre Hospitalier Universitaire de Grenoble; Grenoble France
| | - Benjamin Lemasson
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France
- INSERM; U836 Grenoble France
| | - Anaïck Moisan
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France
- INSERM; U836 Grenoble France
| | - Michel Péoc'h
- Service d'anatomo-pathologie; Centre Hospitalier Universitaire de Saint Etienne; Saint-Etienne France
- EA 2521; Université Jean Monnet; Saint-Etienne France
| | - Chantal Rémy
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France
- INSERM; U836 Grenoble France
| | - Emmanuel L. Barbier
- Université Joseph Fourier; Grenoble Institut des Neurosciences; Grenoble France
- INSERM; U836 Grenoble France
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Buxton RB. The physics of functional magnetic resonance imaging (fMRI). REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2013; 76:096601. [PMID: 24006360 PMCID: PMC4376284 DOI: 10.1088/0034-4885/76/9/096601] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
Functional magnetic resonance imaging (fMRI) is a methodology for detecting dynamic patterns of activity in the working human brain. Although the initial discoveries that led to fMRI are only about 20 years old, this new field has revolutionized the study of brain function. The ability to detect changes in brain activity has a biophysical basis in the magnetic properties of deoxyhemoglobin, and a physiological basis in the way blood flow increases more than oxygen metabolism when local neural activity increases. These effects translate to a subtle increase in the local magnetic resonance signal, the blood oxygenation level dependent (BOLD) effect, when neural activity increases. With current techniques, this pattern of activation can be measured with resolution approaching 1 mm(3) spatially and 1 s temporally. This review focuses on the physical basis of the BOLD effect, the imaging methods used to measure it, the possible origins of the physiological effects that produce a mismatch of blood flow and oxygen metabolism during neural activation, and the mathematical models that have been developed to understand the measured signals. An overarching theme is the growing field of quantitative fMRI, in which other MRI methods are combined with BOLD methods and analyzed within a theoretical modeling framework to derive quantitative estimates of oxygen metabolism and other physiological variables. That goal is the current challenge for fMRI: to move fMRI from a mapping tool to a quantitative probe of brain physiology.
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Affiliation(s)
- Richard B Buxton
- Department of Radiology, University of California, San Diego, USA
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20
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Yablonskiy DA, Sukstanskii AL, He X. Blood oxygenation level-dependent (BOLD)-based techniques for the quantification of brain hemodynamic and metabolic properties - theoretical models and experimental approaches. NMR IN BIOMEDICINE 2013; 26:963-86. [PMID: 22927123 PMCID: PMC3510357 DOI: 10.1002/nbm.2839] [Citation(s) in RCA: 101] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/19/2012] [Accepted: 06/22/2012] [Indexed: 05/06/2023]
Abstract
The quantitative evaluation of brain hemodynamics and metabolism, particularly the relationship between brain function and oxygen utilization, is important for the understanding of normal human brain operation, as well as the pathophysiology of neurological disorders. It can also be of great importance for the evaluation of hypoxia within tumors of the brain and other organs. A fundamental discovery by Ogawa and coworkers of the blood oxygenation level-dependent (BOLD) contrast opened up the possibility to use this effect to study brain hemodynamic and metabolic properties by means of MRI measurements. Such measurements require the development of theoretical models connecting the MRI signal to brain structure and function, and the design of experimental techniques allowing MR measurements to be made of the salient features of theoretical models. In this review, we discuss several such theoretical models and experimental methods for the quantification of brain hemodynamic and metabolic properties. The review's main focus is on methods for the evaluation of the oxygen extraction fraction (OEF) based on the measurement of the blood oxygenation level. A combination of the measurement of OEF and the cerebral blood flow (CBF) allows an evaluation to be made of the cerebral metabolic rate of oxygen consumption (CMRO2 ). We first consider in detail the magnetic properties of blood - magnetic susceptibility, MR relaxation and theoretical models of the intravascular contribution to the MR signal under different experimental conditions. We then describe a 'through-space' effect - the influence of inhomogeneous magnetic fields, created in the extravascular space by intravascular deoxygenated blood, on the formation of the MR signal. Further, we describe several experimental techniques taking advantage of these theoretical models. Some of these techniques - MR susceptometry and T2 -based quantification of OEF - utilize the intravascular MR signal. Another technique - quantitative BOLD - evaluates OEF by making use of through-space effects. In this review, we target both scientists just entering the MR field and more experienced MR researchers interested in the application of advanced BOLD-based techniques to the study of the brain in health and disease.
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21
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Friedrich MG, Karamitsos TD. Oxygenation-sensitive cardiovascular magnetic resonance. J Cardiovasc Magn Reson 2013; 15:43. [PMID: 23706167 PMCID: PMC3681671 DOI: 10.1186/1532-429x-15-43] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 04/29/2013] [Indexed: 12/30/2022] Open
Abstract
Oxygenation-sensitive cardiovascular magnetic resonance (CMR) is a non-contrast technique that allows the non-invasive assessment of myocardial oxygenation. It capitalizes on the fact that deoxygenated hemoglobin in blood can act as an intrinsic contrast agent, changing proton signals in a fashion that can be imaged to reflect the level of blood oxygenation. Increases in O(2) saturation increase the BOLD imaging signal (T2 or T2*), whereas decreases diminish it. This review presents the basic concepts and limitations of the BOLD technique, and summarizes the preclinical and clinical studies in the assessment of myocardial oxygenation with a focus on recent advances. Finally, it provides future directions and a brief look at emerging techniques of this evolving CMR field.
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Affiliation(s)
- Matthias G Friedrich
- Montreal Heart Institute, Departments of Cardiology and Radiology, Université de Montréal, Montreal, QC, Canada
- Departments of Cardiac Sciences and Radiology, University of Calgary, Calgary, Canada
| | - Theodoros D Karamitsos
- Oxford Centre for Clinical Magnetic Resonance Research, Division of Cardiovascular Medicine, Radcliffe Department of Medicine, University of Oxford, John Radcliffe Hospital, Oxford, UK
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22
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Zheng J. Assessment of myocardial oxygenation with MRI. Quant Imaging Med Surg 2013; 3:67-72. [PMID: 23630653 DOI: 10.3978/j.issn.2223-4292.2013.03.01] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Accepted: 03/07/2013] [Indexed: 11/14/2022]
Affiliation(s)
- Jie Zheng
- Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO, USA
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23
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Domsch S, Linke J, Heiler PM, Kroll A, Flor H, Wessa M, Schad LR. Increased BOLD sensitivity in the orbitofrontal cortex using slice-dependent echo times at 3 T. Magn Reson Imaging 2013; 31:201-11. [DOI: 10.1016/j.mri.2012.06.020] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 06/12/2012] [Accepted: 06/21/2012] [Indexed: 10/28/2022]
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Hezel F, Thalhammer C, Waiczies S, Schulz-Menger J, Niendorf T. High spatial resolution and temporally resolved T2* mapping of normal human myocardium at 7.0 Tesla: an ultrahigh field magnetic resonance feasibility study. PLoS One 2012; 7:e52324. [PMID: 23251708 PMCID: PMC3522647 DOI: 10.1371/journal.pone.0052324] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 11/16/2012] [Indexed: 11/19/2022] Open
Abstract
Myocardial tissue characterization using T(2)(*) relaxation mapping techniques is an emerging application of (pre)clinical cardiovascular magnetic resonance imaging. The increase in microscopic susceptibility at higher magnetic field strengths renders myocardial T(2)(*) mapping at ultrahigh magnetic fields conceptually appealing. This work demonstrates the feasibility of myocardial T(2)(*) imaging at 7.0 T and examines the applicability of temporally-resolved and high spatial resolution myocardial T(2)(*) mapping. In phantom experiments single cardiac phase and dynamic (CINE) gradient echo imaging techniques provided similar T(2)(*) maps. In vivo studies showed that the peak-to-peak B(0) difference following volume selective shimming was reduced to approximately 80 Hz for the four chamber view and mid-ventricular short axis view of the heart and to 65 Hz for the left ventricle. No severe susceptibility artifacts were detected in the septum and in the lateral wall for T(2)(*) weighting ranging from TE = 2.04 ms to TE = 10.2 ms. For TE >7 ms, a susceptibility weighting induced signal void was observed within the anterior and inferior myocardial segments. The longest T(2)(*) values were found for anterior (T(2)(*) = 14.0 ms), anteroseptal (T(2)(*) = 17.2 ms) and inferoseptal (T(2)(*) = 16.5 ms) myocardial segments. Shorter T(2)(*) values were observed for inferior (T(2)(*) = 10.6 ms) and inferolateral (T(2)(*) = 11.4 ms) segments. A significant difference (p = 0.002) in T(2)(*) values was observed between end-diastole and end-systole with T(2)(*) changes of up to approximately 27% over the cardiac cycle which were pronounced in the septum. To conclude, these results underscore the challenges of myocardial T(2)(*) mapping at 7.0 T but demonstrate that these issues can be offset by using tailored shimming techniques and dedicated acquisition schemes.
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Affiliation(s)
- Fabian Hezel
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Christof Thalhammer
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany
| | - Sonia Waiczies
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany
- Experimental and Clinical Research Center, a Joint Cooperation between the Charité Medical Faculty and the Max Delbrueck Center for Molecular Medicine, Campus Berlin Buch, Berlin, Germany
| | - Jeanette Schulz-Menger
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany
- Experimental and Clinical Research Center, a Joint Cooperation between the Charité Medical Faculty and the Max Delbrueck Center for Molecular Medicine, Campus Berlin Buch, Berlin, Germany
- Department of Cardiology and Nephrology, HELIOS Klinikum Berlin Buch, Berlin, Germany
| | - Thoralf Niendorf
- Berlin Ultrahigh Field Facility (B.U.F.F.), Max Delbrueck Center for Molecular Medicine, Berlin, Germany
- Experimental and Clinical Research Center, a Joint Cooperation between the Charité Medical Faculty and the Max Delbrueck Center for Molecular Medicine, Campus Berlin Buch, Berlin, Germany
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Ziener CH, Kampf T, Melkus G, Jakob PM, Schlemmer HP, Bauer WR. Signal evolution in the local magnetic field of a capillary — analogy to the damped driven harmonic oscillator. Magn Reson Imaging 2012; 30:540-53. [DOI: 10.1016/j.mri.2011.12.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 11/14/2011] [Accepted: 12/04/2011] [Indexed: 11/29/2022]
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26
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Ziener CH, Kampf T, Reents G, Schlemmer HP, Bauer WR. Spin dephasing in a magnetic dipole field. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 85:051908. [PMID: 23004789 DOI: 10.1103/physreve.85.051908] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 03/12/2012] [Indexed: 06/01/2023]
Abstract
Transverse relaxation by dephasing in an inhomogeneous field is a general mechanism in physics, for example, in semiconductor physics, muon spectroscopy, or nuclear magnetic resonance. In magnetic resonance imaging the transverse relaxation provides information on the properties of several biological tissues. Since the dipole field is the most important part of the multipole expansion of the local inhomogeneous field, dephasing in a dipole field is highly important in relaxation theory. However, there have been no analytical solutions which describe the dephasing in a magnetic dipole field. In this work we give a complete analytical solution for the dephasing in a magnetic dipole field which is valid over the whole dynamic range.
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Affiliation(s)
- C H Ziener
- German Cancer Research Center (DKFZ), Im Neuenheimer Feld 280, 69120 Heidelberg, Germany
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Ureña JRS, Olmos S, Kiselev VG. Tissue-blood exchange of extravascular longitudinal magnetization with account of intracompartmental diffusion. Magn Reson Med 2011; 66:1445-55. [DOI: 10.1002/mrm.22919] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2010] [Revised: 02/11/2011] [Accepted: 02/18/2011] [Indexed: 12/20/2022]
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Jahnke C, Kozerke S, Schnackenburg B, Marx N, Paetsch I. Three-dimensional contrast-enhanced and non-contrast-enhanced cardiac magnetic resonance imaging for the assessment of myocardial ischemic reactions: the practice of looking deeply into the myocardium. J Nucl Cardiol 2011; 18:937-51. [PMID: 21567282 DOI: 10.1007/s12350-011-9391-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- Cosima Jahnke
- Department of Cardiology, University Hospital RWTH Aachen, Pauwelsstrasse 30, 52074, Aachen, Germany.
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Mie MB, Nissen JC, Zöllner FG, Heilmann M, Schoenberg SO, Michaely HJ, Schad LR. Susceptibility weighted imaging (SWI) of the kidney at 3T--initial results. Z Med Phys 2010; 20:143-50. [PMID: 20540905 DOI: 10.1016/j.zemedi.2010.02.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2009] [Revised: 02/25/2010] [Accepted: 02/25/2010] [Indexed: 10/19/2022]
Abstract
Susceptibility weighted imaging provides diagnostic information in strokes, hemorrhages, and cerebral tumors and has proven to be a valuable tool in imaging venous vessels in the cerebrum. The SWI principle is based on the weighting of T(2)* weighted magnitude images with a phase mask, therewith improving image contrast of veins or neighbouring structures of different susceptibility, in general. T(2)* weighted MRI is already used for assessment of kidney function. In this paper, the feasibility of SWI on kidneys was investigated. Translation of SWI from the brain to the kidneys comes along with two main challenges: (i) organ motion due to breathing and (ii) a higher oxygenation level of renal veins compared to the brain. To handle these problems, the acquisition time has been cut down to allow for breath-hold examinations, and different post-processing methods including a new phase mask were investigated to visualize renal veins. Results showed that by a new post-processing strategy SWI contrast was enhanced on average by a factor of 1.33 compared to the standard phase mask. In summary, initial experiences of SWI on the kidneys demonstrated the feasibility. However, further technical developments have to be performed to make this technology applicable in clinical abdominal MRI.
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Affiliation(s)
- Moritz B Mie
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Heidelberg University, Germany.
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Zhou X, Tang R, Klein R, Li D, Dharmakumar R. Parametric dependence of myocardial blood oxygen level dependent, balanced steady-state free-precession imaging at 1.5 T: Theory and experiments. Magn Reson Med 2010; 63:484-93. [DOI: 10.1002/mrm.22240] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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31
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Ziener CH, Glutsch S, Jakob PM, Bauer WR. Spin dephasing in the dipole field around capillaries and cells: numerical solution. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 80:046701. [PMID: 19905476 DOI: 10.1103/physreve.80.046701] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Indexed: 05/28/2023]
Abstract
We numerically solve the Bloch-Torrey equation by discretizing the differential operators in real space using finite differences. The differential equation is either solved directly in time domain as initial-value problem or in frequency domain as boundary-value problem. Especially the solution in time domain is highly efficient and suitable for arbitrary domains and dimensions. As examples, we calculate the average magnetization and the frequency distribution for capillaries and cells which are idealized as cylinders and spheres, respectively. The solution is compared with the commonly used Gaussian approximation and the strong-collision approximation. While these approximations become exact in limiting cases (small or large diffusion coefficient), they strongly deviate from the numerical solution for intermediate values of the diffusion coefficient.
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Affiliation(s)
- C H Ziener
- Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Würzburg, Germany
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32
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Meloni A, Pepe A, Positano V, Favilli B, Maggio A, Capra M, Lo Pinto C, Gerardi C, Santarelli MF, Midiri M, Landini L, Lombardi M. Influence of myocardial fibrosis and blood oxygenation on heart T2* values in thalassemia patients. J Magn Reson Imaging 2009; 29:832-7. [DOI: 10.1002/jmri.21704] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Affiliation(s)
- Antonella Meloni
- MRI Laboratory, Institute of Clinical Physiology, G. Monasterio Foundation, Pisa, Italy.
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33
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Ziener CH, Kampf T, Herold V, Jakob PM, Bauer WR, Nadler W. Frequency autocorrelation function of stochastically fluctuating fields caused by specific magnetic field inhomogeneities. J Chem Phys 2008; 129:014507. [DOI: 10.1063/1.2949097] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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34
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Dharmakumar R, Arumana JM, Tang R, Harris K, Zhang Z, Li D. Assessment of regional myocardial oxygenation changes in the presence of coronary artery stenosis with balanced SSFP imaging at 3.0T: Theory and experimental evaluation in canines. J Magn Reson Imaging 2008; 27:1037-45. [DOI: 10.1002/jmri.21345] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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35
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Egred M, Waiter GD, Redpath TW, Semple SKI, Al-Mohammad A, Walton S. Blood oxygen level-dependent (BOLD) MRI: A novel technique for the assessment of myocardial ischemia as identified by nuclear imaging SPECT. Eur J Intern Med 2007; 18:581-6. [PMID: 18054708 DOI: 10.1016/j.ejim.2007.03.013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2006] [Revised: 03/15/2007] [Accepted: 03/16/2007] [Indexed: 11/26/2022]
Abstract
BACKGROUND The different levels of deoxyhemoglobin in the ischemic myocardium, induced by stressors such as dipyridamole, can be detected by blood oxygen level-dependent (BOLD) MRI and may be used to diagnose myocardial ischemia. The aim of this study was to assess the signal change in the myocardium on BOLD MRI as well as wall thickening between rest and dipyridamole stress images in ischemic and non-ischemic myocardium as identified on SPECT imaging. METHODS Twelve patients with stress-induced myocardial ischemia on SPECT underwent rest and dipyridamole stress MRI using a double breath-hold, T2()-weighted, ECG-gated sequence to produce BOLD contrast images as well as cine-MRI for wall thickening assessment in 10 of the 12 patients. Signal change on BOLD MRI and wall thickening were compared between rest and stress images in ischemic and non-ischemic myocardial segments as identified on SPECT. In each patient, two MRI slices containing 16 segments per slice were analysed. RESULTS In total, there were 384 segments for BOLD analysis and 320 for wall thickening. For BOLD signal 137 segments correlated to segments with reversible ischemia on SPECT and 247 to normal segments, while for wall thickening 112 segments correlated to segments with reversible ischemia and 208 to normal segments. The average BOLD MRI signal intensity change was -13.8 (+/-16.3)% in the ischemic segments compared to -10.3 (+/-14.7)% in the non-ischemic segments (p=0.05). The average wall thickening was 6.4 (+/-3.4) mm in the ischemic segments compared to 8.7 (+/-3.8) mm in the non-ischemic segments (p<0.0001). CONCLUSION Stress-induced ischemic myocardium has a different signal change and wall thickening than non-ischemic myocardium and may be differentiated on BOLD MRI. Larger studies are needed to define a threshold for detection and to determine the sensitivity and specificity of this technique.
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Affiliation(s)
- M Egred
- Cardio-thoracic Centre, Thomas Drive, Liverpool L14 3PE, UK
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36
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Argyropoulou MI, Astrakas L. MRI evaluation of tissue iron burden in patients with beta-thalassaemia major. Pediatr Radiol 2007; 37:1191-200; quiz 1308-9. [PMID: 17710390 PMCID: PMC2292491 DOI: 10.1007/s00247-007-0567-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2007] [Revised: 05/07/2007] [Accepted: 05/31/2007] [Indexed: 11/24/2022]
Abstract
beta-Thalassaemia major is a hereditary haemolytic anaemia that is treated with multiple blood transfusions. A major complication of this treatment is iron overload, which leads to cell death and organ dysfunction. Chelation therapy, used for iron elimination, requires effective monitoring of the body burden of iron, for which serum ferritin levels and liver iron content measured in liver biopsies are used as markers, but are not reliable. MRI based on iron-induced T2 relaxation enhancement can be used for the evaluation of tissue siderosis. Various MR protocols using signal intensity ratio and mainstream relaxometry methods have been used, sometimes with discrepant results. Relaxometry methods using multiple echoes achieve better sampling of the time domain in which relaxation mechanisms take place and lead to more precise results. In several studies the MRI parameters of liver siderosis have failed to correlate with those of other affected organs, underlining the necessity for MRI iron evaluation in individual organs. Most studies have included children in the evaluated population, but MRI data on very young children are lacking. Wider application of relaxometry methods is indicated, with the establishment of universally accepted MRI protocols, and further studies, including young children, are needed.
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Affiliation(s)
- Maria I Argyropoulou
- Radiology Department, Medical School, University of Ioannina, Ioannina, GR-45110, Greece.
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37
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Ziener CH, Kampf T, Melkus G, Herold V, Weber T, Reents G, Jakob PM, Bauer WR. Local frequency density of states around field inhomogeneities in magnetic resonance imaging: effects of diffusion. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:031915. [PMID: 17930279 DOI: 10.1103/physreve.76.031915] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2006] [Revised: 04/27/2007] [Indexed: 05/25/2023]
Abstract
A method describing NMR-signal formation in inhomogeneous tissue is presented which covers all diffusion regimes. For this purpose, the frequency distribution inside the voxel is described. Generalizing the results of the well-known static dephasing regime, we derive a formalism to describe the frequency distribution that is valid over the whole dynamic range. The expressions obtained are in agreement with the results obtained from Kubos line-shape theory. To examine the diffusion effects, we utilize a strong collision approximation, which replaces the original diffusion process by a simpler stochastic dynamics. We provide a generally valid relation between the frequency distribution and the local Larmor frequency inside the voxel. To demonstrate the formalism we give analytical expressions for the frequency distribution and the free induction decay in the case of cylindrical and spherical magnetic inhomogeneities. For experimental verification, we performed measurements using a single-voxel spectroscopy method. The data obtained for the frequency distribution, as well as the magnetization decay, are in good agreement with the analytic results, although experiments were limited by magnetic field gradients caused by an imperfect shim and low signal-to-noise ratio.
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Affiliation(s)
- C H Ziener
- Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany
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38
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Maris TG, Papakonstantinou O, Chatzimanoli V, Papadakis A, Pagonidis K, Papanikolaou N, Karantanas A, Gourtsoyiannis N. Myocardial and liver iron status using a fast T*2 quantitative MRI (T*2qMRI) technique. Magn Reson Med 2007; 57:742-53. [PMID: 17390359 DOI: 10.1002/mrm.21204] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
This work demonstrates the use of a fast and precise methodology for evaluating myocardial and liver iron status in multitransfused thalassemic patients by means of a fast T(2) (*) quantitative MRI (T(2) (*)qMRI) technique. Myocardial and liver T(2) (*) values were calculated in 48 thalassemic patients and 21 normal subjects on a 1.5T MRI system using a breath-hold 2D single-slice multiecho gradient-echo (MEGRE) sequence (16 echoes, TR/TE1/TE16/FA = 160/2.7/37.65 ms/25 degrees ). No ECG gating was used. Myocardial T(2) (*), liver T(2) (*), and myocardial to muscle (CR/MS) and liver to muscle (LV/MS) T(2) (*) ratios were correlated with serum ferritin concentration (SFC) levels for all patients. Significant differences in myocardial and liver mean T(2) (*), CR/MS, and LV/MS T(2) (*) values between patients and normal subjects were found (P < 0.0005). Differences in paraspinous muscle mean T(2) (*) values between patients and normal subjects were not significant. Myocardial T(2) (*) and CR/MS T(2) (*) values were not correlated with SFC levels. Liver T(2) (*) and LV/MS T(2) (*) values were significantly correlated with SFC (r = 0.540, P < 0.0005). Myocardial T(2) (*) and CR/MS T(2) (*) values were not correlated with either liver T(2) (*) or LV/MS T(2) (*) values, respectively. We conclude that myocardial and liver iron deposition can be evaluated using the fast non-ECG-gated T(2) (*)qMRI technique.
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Affiliation(s)
- Thomas G Maris
- Department of Medical Physics, University Hospital of Heraklion, University of Crete, Heraklion/Crete, Greece.
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39
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Zhong K, Leupold J, Hennig J, Speck O. Systematic investigation of balanced steady-state free precession for functional MRI in the human visual cortex at 3 Tesla. Magn Reson Med 2007; 57:67-73. [PMID: 17191247 DOI: 10.1002/mrm.21103] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Previous studies have applied balanced steady-state free precession (bSSFP) to functional brain imaging. Methods that exploit the strong frequency dependence of the MR signal in the bSSFP transition band are strongly affected by field inhomogeneity and frequency drifts. Recent bSSFP studies using "on-resonance" (in the bSSFP passband) acquisition claimed that higher sensitivity was achieved compared to traditional fMRI methods. However, the contrast mechanism that generates activation-related signal changes in bSSFP imaging is not yet fully understood. We performed a systematic study of on-resonance bSSFP signal behavior using a multiecho balanced SSFP sequence with different TRs at 3 Tesla. We conclude that intravoxel dephasing, or the off-resonance averaged steady state, dominates the bSSFP signal decay and determines the bSSFP fMRI contrast. Experimental findings were confirmed by simulations based on existing theories for signal formation around blood vessels in inhomogeneous tissues. The activation-induced signal change in on-resonance bSSFP increases with TE, and the TE dependence of the contrast-to-noise ratio (CNR) in bSSFP is similar to that in gradient echo-planar imaging (GE-EPI). However, GE-EPI has a significantly higher CNR efficiency.
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Affiliation(s)
- Kai Zhong
- Department of Diagnostic Radiology, Medical Physics, University Hospital Freiburg, Freiburg, Germany.
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40
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Egred M, Waiter GD, Semple SIK, Redpath TW, Al-Mohammad A, Norton MY, Metcalfe MJ, Walton S. Blood oxygen level-dependent (BOLD) magnetic resonance imaging in patients with dypiridamole induced ischaemia; a PET comparative study. Int J Cardiol 2007; 115:36-41. [PMID: 16824632 DOI: 10.1016/j.ijcard.2006.01.054] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2005] [Accepted: 01/27/2006] [Indexed: 11/24/2022]
Abstract
BACKGROUND Blood oxygen level-dependent (BOLD) MRI relies on changes in deoxyhaemoglobin level in tissues under stress for signal variation and may be used for detection of ischaemic myocardium. METHODS 15 patients with stress induced myocardial ischaemia on PET scanning underwent rest and dypiridamole stress MRI using a double breath-hold T2-weighted, ECG gated sequence to produce BOLD contrast images and cine-MRI for wall thickening assessment. Signal change on BOLD MRI and wall thickening were compared between rest and stress images in ischaemic and non-ischaemic myocardial segments. RESULTS Using PET, 156 segments were identified with reversible ischaemia and 324 as non-ischaemic. The ischaemic segments were found on BOLD MRI to have an average signal change between rest and stress of -16.7% compared to -14% in the non-ischaemic segments (p=0.04). The average wall thickening was 7.8 mm in the ischaemic segments compared with 9.5 mm in the non-ischaemic segments (p<0.0001). CONCLUSION BOLD MRI with wall thickening assessment may differentiate ischaemic from non-ischaemic myocardium in patients with stress induced myocardial ischaemia. Larger studies with improved spatial resolution would help define a threshold for detection of ischaemia as well as determine this technique's sensitivity and specificity.
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Affiliation(s)
- M Egred
- Cardiology Department, Cardio-thoracic Centre, Thomas Drive, Liverpool L14 3PE, UK.
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41
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Ziener CH, Kampf T, Melkus G, Jakob PM, Bauer WR. Scaling laws for transverse relaxation times. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 184:169-75. [PMID: 17045825 DOI: 10.1016/j.jmr.2006.09.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Revised: 09/18/2006] [Accepted: 09/22/2006] [Indexed: 05/12/2023]
Abstract
Simple scaling laws are useful tools in understanding the effect of changing parameters in MRI experiments. In this paper the general scaling behavior of the transverse relaxation times is discussed. We consider the dephasing of spins diffusing around a field inhomogeneity inside a voxel. The strong collision approximation is used to describe the diffusion process. The obtained scaling laws are valid over the whole dynamic range from motional narrowing to static dephasing. The dependence of the relaxation times on the external magnetic field, diffusion coefficients of the surrounding medium, and the characteristic scale of the field inhomogeneity is analyzed. For illustration the generally valid scaling laws are applied to the special case of a capillary, usually used as a model of the myocardial BOLD effect.
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Affiliation(s)
- C H Ziener
- Bayerische Julius-Maximilians-Universität Würzburg, Institut für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany.
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Egred M, Waiter GD, Al-Mohammad A, Semple SIK, Redpath TW, Walton S. Blood oxygen level dependent (BOLD) MRI: A novel technique for the detection of myocardial ischemia. Eur J Intern Med 2006; 17:551-5. [PMID: 17142173 DOI: 10.1016/j.ejim.2006.04.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2006] [Revised: 04/09/2006] [Accepted: 04/27/2006] [Indexed: 10/23/2022]
Abstract
BACKGROUND Blood oxygen level dependent (BOLD) T2* MRI detects signal variance within the myocardium based on changes in the deoxyhaemoglobin level following pharmacological stress, and it has the potential to identify areas of myocardial ischemia. The aim of the present study was to assess the utility of BOLD T2* MRI in the detection of myocardial ischemia in patients with an existing diagnosis of coronary artery disease. METHOD Twenty-one patients with established three-vessel coronary artery disease on coronary angiography underwent rest and dipyridamole stress MRI using a double breath-hold T2* weighted ECG gated sequence. Analysis was performed on multiple short-axis slices of the heart, projected as a bull's eye. The myocardium was divided into three coronary territories, yielding 63 territories in total. A signal change between rest and stress of more than +/-4% was significant, implying a change in deoxyhaemoglobin concentration. A signal decrease or no changes denote the presence of ischemia, while a signal increase indicates no ischemia. RESULTS All images were of sufficient quality for signal intensity analysis. In 12/63 territories (19%), a significant signal increase following stress was detected. A significant signal decrease was detected in 34/63 territories (54%), and in 17/63 territories (27%) there was a non-significant change. The presence of a perfusion defect was identified, therefore, in 51/63 (81%), based on the signal difference between rest and stress. CONCLUSION Changes in myocardial oxygen level appear to be detectable by BOLD T2* MRI without using contrast media. Further, larger comparative studies are required to evaluate the diagnostic and prognostic impact of this technique and to compare it to the gold standard methods for the detection of myocardial ischemia.
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Affiliation(s)
- M Egred
- Cardiology Department, Cardiothoracic Centre, Liverpool, UK
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43
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Ziener CH, Bauer WR, Melkus G, Weber T, Herold V, Jakob PM. Structure-specific magnetic field inhomogeneities and its effect on the correlation time. Magn Reson Imaging 2006; 24:1341-7. [PMID: 17145406 DOI: 10.1016/j.mri.2006.08.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2006] [Accepted: 08/25/2006] [Indexed: 10/24/2022]
Abstract
We describe the relationship between the correlation time and microscopic spatial inhomogeneities in the static magnetic field. The theory takes into account diffusion of nuclear spins in the inhomogeneous field created by magnetized objects. A simple general expression for the correlation time is obtained. It is shown that the correlation time is dependent on a characteristic length, the diffusion coefficient of surrounding medium, the permeability of the surface and the volume fraction of the magnetized objects. For specific geometries (spheres and cylinders), exact analytical expressions for the correlation time are given. The theory can be applied to contrast agents (magnetically labeled cells), capillary network, BOLD effect and so forth.
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Affiliation(s)
- Christian H Ziener
- Bayerische Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, 97074 Würzburg, Germany.
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Ziener CH, Bauer WR, Jakob PM. Frequency distribution and signal formation around a vessel. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2005; 18:225-30. [PMID: 16175391 DOI: 10.1007/s10334-005-0122-8] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2005] [Revised: 07/19/2005] [Accepted: 07/19/2005] [Indexed: 10/25/2022]
Abstract
We describe the NMR signal formation properties of a single vessel. Instead of assuming the frequency distribution to be a simple Lorentzian or Gaussian one, we take into account that the frequency distribution around the vessel is a complex function. Considering the static dephasing regime we find a relationship between signal formation and frequency distribution. Analytical expressions for the frequency distribution in a voxel and the magnetization decay are obtained. In the case of small volume fractions of blood and week magnetic fields the results can be used for describing signal formation processes in a vascular network. A relationship between the frequency distribution and the properties of the vascular network is derived. The magnetization decay in different time regimes is discussed. The result is relevant for describing signal formation processes around a vessel for arbitrary pulse sequences.
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Affiliation(s)
- C H Ziener
- Bayerische Julius-Maximilians-Universität Würzburg, Lehrstuhl für Experimentelle Physik 5, Am Hubland, 97074, Würzburg, Germany.
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Utz W, Jordan J, Niendorf T, Stoffels M, Luft FC, Dietz R, Friedrich MG. Blood Oxygen Level–Dependent MRI of Tissue Oxygenation. Arterioscler Thromb Vasc Biol 2005; 25:1408-13. [PMID: 15890970 DOI: 10.1161/01.atv.0000170131.13683.d7] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVES The contribution of endothelial function to tissue oxygenation is not well understood. Muscle blood oxygen level-dependent MRI (BOLD MRI) provides data largely dependent on hemoglobin (Hb) oxygenation. We used BOLD MRI to assess endothelium-dependent signal intensity (SI) changes. METHODS AND RESULTS We investigated mean BOLD SI changes in the forearm musculature using a gradient-echo technique at 1.5 T in 9 healthy subjects who underwent a protocol of repeated acetylcholine infusions at 2 different doses (16 and 64 microg/min) and N(G)-monomethyl-L-arginine (L-NMMA; 5 mg/min) into the brachial artery. Sodium nitroprusside was used as a control substance. For additional correlation with standard methods, the same protocol was repeated, and forearm blood flow was measured by strain gauge plethysmography. We obtained a significant increase in BOLD SI during acetylcholine infusion (64 microg/min) and a significant decrease for L-NMMA infusion (P<0.005 for both). BOLD SI showed a different kinetic signal than did blood flow, particularly after intermittent ischemia and at high flow rates. CONCLUSIONS In standard endothelial function tests, BOLD MRI detects a dissociation of tissue Hb oxygenation from blood flow. BOLD MRI may be a useful adjunct in assessing endothelial function.
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Affiliation(s)
- Wolfgang Utz
- Medical Faculty of the Charité, Franz Volhard Klinik HELIOS Klinikum-Berlin at the Max Delbrück Center for Molecular Medicine, Berlin, Germany
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Ziener CH, Bauer WR, Jakob PM. Transverse relaxation of cells labeled with magnetic nanoparticles. Magn Reson Med 2005; 54:702-6. [PMID: 16086369 DOI: 10.1002/mrm.20634] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We describe the NMR relaxation properties of magnetically labeled cells. The cells are labeled with magnetic nanoparticles (SPIO, USPIO), which generate susceptibility contrast. The geometry of the labeled cells and the surrounding tissue is considered. We assume that the magnetic nanoparticles accumulate to form a magnetic core of radius RC inside the cell. The correlation time tau, which describes the motion of spins around this core, is analyzed. Using the strong collision approach, explicit expressions are derived for the transverse relaxation rate R2* for tissue containing labeled cells as a function of the core radius, the diffusion coefficient, and the concentration of the nanoparticles. The predictions of this model agree well with numerical simulations and experimental data.
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Affiliation(s)
- C H Ziener
- Bayerische Julius-Maximilians-Universität Würzburg, Institut für Experimentelle Physik 5, Am Hubland, 97074 Würzburg, Germany.
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Abstract
This article reviews the current MR imaging literature with respect to ischemic heart disease and focuses on the clinical practicalities of cardiac MR imaging today.
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48
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Egred M, Al-Mohammad A, Waiter GD, Redpath TW, Semple SK, Norton M, Welch A, Walton S. Detection of scarred and viable myocardium using a new magnetic resonance imaging technique: blood oxygen level dependent (BOLD) MRI. Heart 2003; 89:738-44. [PMID: 12807845 PMCID: PMC1767717 DOI: 10.1136/heart.89.7.738] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND The identification of viable myocardium in patients with impaired left ventricular contraction secondary to coronary heart disease is important clinically as such myocardium is likely to benefit from revascularisation. Blood oxygen level dependent (BOLD) magnetic resonance imaging (MRI) relies on changes in deoxyhaemoglobin concentration under stress for signal generation and could be used for the differentiation between scarred and viable myocardium. AIM To assess the signal change on BOLD MRI in viable and scarred myocardium as identified by positron emission tomography (PET). METHOD 19 patients with impaired left ventricular contraction and at least one akinetic area were enrolled. They underwent rest and dipyridamole stress MRI, using a double breath hold T2* weighted, ECG gated sequence to produce BOLD contrast images, and cine-MRI for wall thickening assessment. Dynamic perfusion and metabolic PET images followed the MRI. Signal change on BOLD MRI and the wall thickening were compared between rest and stress images in hibernating and scarred segments identified by PET on two short axis slices of mid ventricle, with eight segments each. RESULTS Using PET, 68 segments were identified as hibernating and 42 as scarred. The hibernating segments were found on BOLD MRI to have an average signal change between rest and stress of -9.53%, compared with -2.15% in the scarred segments (p = 0.008). The average wall thickening was 8.7 mm in the hibernating segments compared with 5.9 mm in the scarred segments (p < 0.0001). CONCLUSIONS BOLD MRI with wall thickening may differentiate scarred and viable myocardium and help identify suitable patients for revascularisation. Further larger studies are needed to establish a threshold for detection, sensitivity, and specificity.
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Affiliation(s)
- M Egred
- Cardiac Department, University Hospital Aintree, Liverpool, UK.
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49
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Foltz WD, Al-Kwifi O, Sussman MS, Stainsby JA, Wright GA. Optimized spiral imaging for measurement of myocardial T2 relaxation. Magn Reson Med 2003; 49:1089-97. [PMID: 12768587 DOI: 10.1002/mrm.10467] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Microcirculation oxygen levels and blood volumes should be reflected in measurements of myocardial T(2) relaxation. This work describes the optimization of a spiral imaging strategy for robust myocardial T(2) measurement to minimize the standard deviation of T(2) measurement (sigmaT(2)). Theoretical and experimental studies of blurring at muscle/blood interfaces enabled the derivation of parameter sets which reduce sigma T(2) to the level of 5%. T(2) relaxation mapping within healthy volunteers provided estimation of residual sigmaT(2) within the optimized technique. The standard deviation in T(2) measurement across regions of interest (ROIs) in different locations is about 9%. The standard deviation in T(2) measurement in an ROI across different time points is about 5%.
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Affiliation(s)
- Warren D Foltz
- Department of Medical Biophysics, University of Toronto, Canada.
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50
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Sun PZ, Schoening ZB, Jasanoff A. In vivo oxygen detection using exogenous hemoglobin as a contrast agent in magnetic resonance microscopy. Magn Reson Med 2003; 49:609-14. [PMID: 12652529 DOI: 10.1002/mrm.10405] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
In this work we show that exogenous molecular hemoglobin (Hb) is an effective indicator of relative local oxygen tension in magnetic resonance (MR) microscopy studies in vivo. This approach is more sensitive than other MRI oximetry methods; it can be used at higher resolutions and in specimens with no blood oxygen level-dependent (BOLD) effects. Using injection studies in flies, we show that Hb can permeate through relatively dense neural tissue, and that it is not obviously disruptive to physiology. Hb-injected flies show large changes in signal intensity (40-50%) when external O(2) levels are manipulated artificially from 0% to 21%. Oxygen-dependent contrast changes produced by exogenous Hb are detected in T(2)-weighted imaging experiments, and can be roughly calibrated if necessary. These studies demonstrate the feasibility of a contrast agent technique that may be useful for functional MRI (fMRI) studies of metabolism at tens of microns resolution.
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Affiliation(s)
- Phillip Z Sun
- Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA
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