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Ruh A, Emerich P, Scherer H, Novikov DS, Kiselev VG. Observation of magnetic structural universality and jamming transition with NMR. J Magn Reson 2023; 353:107476. [PMID: 37392588 DOI: 10.1016/j.jmr.2023.107476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2023] [Revised: 05/07/2023] [Accepted: 05/08/2023] [Indexed: 07/03/2023]
Abstract
Nuclear magnetic resonance (NMR) has been instrumental in deciphering the structure of proteins. Here we show that transverse NMR relaxation, through its time-dependent relaxation rate, is distinctly sensitive to the structure of complex materials or biological tissues at the mesoscopic scale, from micrometers to tens of micrometers. Based on the ideas of universality, we show analytically and numerically that the time-dependent transverse relaxation rate approaches its long-time limit in a power-law fashion, with the dynamical exponent reflecting the universality class of mesoscopic magnetic structure. The spectral line shape acquires the corresponding non-analytic power law singularity at zero frequency. We experimentally detect the change in the dynamical exponent as a result of the transition into maximally random jammed state characterized by hyperuniform correlations. The relation between relaxational dynamics and magnetic structure opens the way for noninvasive characterization of porous media, complex materials and biological tissues.
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Affiliation(s)
- Alexander Ruh
- Medical Physics, Department of Radiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Philipp Emerich
- Medical Physics, Department of Radiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Harald Scherer
- Institute of Inorganic and Analytical Chemistry, University of Freiburg, Freiburg, Germany
| | - Dmitry S Novikov
- Bernard and Irene Schwartz Center for Biomedical Imaging, Department of Radiology, New York University School of Medicine, New York, NY, USA
| | - Valerij G Kiselev
- Medical Physics, Department of Radiology, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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Naresh NK, Misener S, Zhang Z, Yang C, Ruh A, Bertolino N, Epstein FH, Collins JD, Markl M, Procissi D, Carr JC, Allen BA. Cardiac MRI Myocardial Functional and Tissue Characterization Detects Early Cardiac Dysfunction in a Mouse Model of Chemotherapy-Induced Cardiotoxicity. NMR Biomed 2020; 33:e4327. [PMID: 32567177 DOI: 10.1002/nbm.4327] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 04/14/2020] [Accepted: 05/06/2020] [Indexed: 06/11/2023]
Abstract
BACKGROUND Doxorubicin and doxorubicin-trastuzumab combination chemotherapy have been associated with cardiotoxicity that eventually leads to heart failure and may limit dose-effective cancer treatment. Current diagnostic strategies rely on decreased ejection fraction (EF) to diagnose cardiotoxicity. PURPOSE The aim of this study is to explore the potential of cardiac MR (CMR) imaging to identify imaging biomarkers in a mouse model of chemotherapy-induced cardiotoxicity. METHODS A cumulative dose of 25 mg/kg doxorubicin was administered over three weeks using subcutaneous pellets (n = 9, Dox). Another group (n = 9) received same dose of Dox and a total of 10 mg/kg trastuzumab (DT). Mice were imaged at baseline, 5/6 weeks and 10 weeks post-treatment on a 7T MRI system. The protocol included short-axis cine MRI covering the left ventricle (LV) and mid-ventricular short-axis tissue phase mapping (TPM), pre- and post-contrast T1 mapping, T2 mapping and Displacement Encoding with Stimulated Echoes (DENSE) strain encoded MRI. EF, peak myocardial velocities, native T1, T2, extracellular volume (ECV), and myocardial strain were quantified. N = 7 mice were sacrificed for histopathologic assessment of apoptosis at 5/6 weeks. RESULTS Global peak systolic longitudinal velocity was reduced at 5/6 weeks in Dox (0.6 ± 0.3 vs 0.9 ± 0.3, p = 0.02). In the Dox group, native T1 was reduced at 5/6 weeks (1.3 ± 0.2 ms vs 1.6 ± 0.2 ms, p = 0.02), and relatively normalized at week 10 (1.4 ± 0.1 ms vs 1.6 ± 0.2 ms, p > 0.99). There was no change in EF and other MRI parameters and histopathologic results demonstrated minimal apoptosis in all mice (~1-2 apoptotic cell/high power field), suggesting early-stage cardiotoxicity. CONCLUSIONS In a mouse model of chemotherapy-induced cardiotoxicity using doxorubicin and trastuzumab, advanced CMR shows promise in identifying treatment-related decrease in myocardial velocity and native T1 prior to the onset of cardiomyocyte apoptosis and reduction of EF.
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Affiliation(s)
- Nivedita K Naresh
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Sol Misener
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Zhouli Zhang
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Cynthia Yang
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Alexander Ruh
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Nicola Bertolino
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Frederick H Epstein
- Department of Biomedical Engineering, University of Virginia, Charlottesville, VA, USA
| | - Jeremy D Collins
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
- Department of Radiology, Mayo Clinic, Rochester, MN, USA
| | - Michael Markl
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
- McCormick School of Engineering, Northwestern University, Chicago, IL, USA
| | - Daniele Procissi
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - James C Carr
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
| | - Bradley A Allen
- Department of Radiology, Northwestern University, 737 N. Michigan Ave, Chicago, IL, USA
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Ferrazzi G, Bassenge JP, Mayer J, Ruh A, Roujol S, Ittermann B, Schaeffter T, Cordero-Grande L, Schmitter S. Autocalibrated cardiac tissue phase mapping with multiband imaging and k-t acceleration. Magn Reson Med 2020; 84:2429-2441. [PMID: 32306471 DOI: 10.1002/mrm.28288] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Revised: 03/05/2020] [Accepted: 03/28/2020] [Indexed: 12/25/2022]
Abstract
PURPOSE To develop an autocalibrated multiband (MB) CAIPIRINHA acquisition scheme with in-plane k-t acceleration enabling multislice three-directional tissue phase mapping in one breath-hold. METHODS A k-t undersampling scheme was integrated into a time-resolved electrocardiographic-triggered autocalibrated MB gradient-echo sequence. The sequence was used to acquire data on 4 healthy volunteers with MB factors of two (MB2) and three (MB3), which were reconstructed using a joint reconstruction algorithm that tackles both k-t and MB acceleration. Forward simulations of the imaging process were used to tune the reconstruction model hyperparameters. Direct comparisons between MB and single-band tissue phase-mapping measurements were performed. RESULTS Simulations showed that the velocities could be accurately reproduced with MB2 k-t (average ± twice the SD of the RMS error of 0.08 ± 0.22 cm/s and velocity peak reduction of 1.03% ± 6.47% compared with fully sampled velocities), whereas acceptable results were obtained with MB3 k-t (RMS error of 0.13 ± 0.58 cm/s and peak reduction of 2.21% ± 13.45%). When applied to tissue phase-mapping data, the proposed technique allowed three-directional velocity encoding to be simultaneously acquired at two/three slices in a single breath-hold of 18 heartbeats. No statistically significant differences were detected between MB2/MB3 k-t and single-band k-t motion traces averaged over the myocardium. Regional differences were found, however, when using the American Heart Association model for segmentation. CONCLUSION An autocalibrated MB k-t acquisition/reconstruction framework is presented that allows three-directional velocity encoding of the myocardial velocities at multiple slices in one breath-hold.
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Affiliation(s)
- Giulio Ferrazzi
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Jean Pierre Bassenge
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
- Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max-Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Johannes Mayer
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Alexander Ruh
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Sébastien Roujol
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Bernd Ittermann
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
| | - Tobias Schaeffter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
- FG Medizintechnik, Technische Universität Berlin, Berlin, Germany
| | - Lucilio Cordero-Grande
- Biomedical Image Technologies, ETSI Telecomunicación, Universidad Politécnica de Madrid & CIBER-BBN, Madrid, Spain
- Centre for the Developing Brain, School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Sebastian Schmitter
- Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany
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Sarnari R, Blake AM, Ruh A, Abbasi MA, Pathrose A, Blaisdell J, Dolan RS, Ghafourian K, Wilcox JE, Khan SS, Vorovich EE, Rich JD, Anderson AS, Yancy CW, Carr JC, Markl M. Evaluating Biventricular Myocardial Velocity and Interventricular Dyssynchrony in Adult Patients During the First Year After Heart Transplantation. J Magn Reson Imaging 2020; 52:920-929. [PMID: 32061045 DOI: 10.1002/jmri.27091] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 01/28/2020] [Accepted: 01/30/2020] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Magnetic resonance tissue phase mapping (TPM) measures three-directional myocardial velocities of the left and right ventricle (LV, RV). This noninvasive technique may supplement endomyocardial biopsy (EMB) in monitoring grafts post-heart transplantation (HTx). PURPOSE To assess biventricular myocardial velocity alterations in grafts and investigate the relationship between velocities and acute cellular rejection (ACR) episodes. STUDY TYPE Prospective. SUBJECTS Twenty-seven patients within 1 year post-HTx (49 ± 13 years, 19 M) and 18 age-matched controls (49 ± 15 years, 12 M). FIELD STRENGTH/SEQUENCE 1.5T, 2D balanced steady-state free precession, and TPM. ASSESSMENT Ventricular function: end-diastolic and end-systolic volumes, stroke volumes, ejection fraction (EF), and myocardial mass. TPM velocities: peak-systolic and peak-diastolic velocities, cardiac twist, and interventricular dyssynchrony. ACR rejection episodes: International Society for Heart and Lung Transplantation grading of EMB specimens. STATISTICAL TESTS The Lilliefors test for normality, unpaired t-tests, and Wilcoxon rank-sum tests for normally and nonnormally distributed data, respectively, were used, as well as multivariate regression for confounding variables and Pearson's correlation for associations between TPM velocities and global function. RESULTS Compared to controls, HTx patients demonstrated reduced biventricular systolic longitudinal velocities (LV: 5.2 ± 2.1 vs. 4.0 ± 1.5 cm/s, P < 0.05; RV: 4.2 ± 1.3 vs. 3.1 ± 1.2 cm/s, P < 0.01). Correlation analysis revealed significant positive relationships for biventricular EF with radial peak velocities of the same ventricle in both systole and diastole (LV systole: r = 0.48, P < 0.01; LV diastole: r = 0.28, P < 0.05; RV systole: r = 0.35, P < 0.01; RV diastole: r = 0.36, P < 0.01). Segmentally, longitudinal velocities were impaired in 7/16 LV segments and 5/10 RV segments in systole and 7/10 RV segments in diastole. TPM analysis in studies with >4 preceding ACR episodes showed globally reduced RV and LV systolic radial velocity, and segmentally reduced radial and longitudinal systolic velocities. DATA CONCLUSION Biventricular global and segmental velocities were reduced in HTx patients. Patients with >4 rejection episodes showed reduced myocardial velocities. The TPM sequence may add functional information for monitoring graft dysfunction. LEVEL OF EVIDENCE 2 TECHNICAL EFFICACY STAGE: 2 J. Magn. Reson. Imaging 2020;52:920-929.
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Affiliation(s)
- Roberto Sarnari
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Allison M Blake
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Alexander Ruh
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Muhannad A Abbasi
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Ashitha Pathrose
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Julie Blaisdell
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Ryan S Dolan
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Kambiz Ghafourian
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Jane E Wilcox
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Sadiya S Khan
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Esther E Vorovich
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Jonathan D Rich
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Allen S Anderson
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Clyde W Yancy
- Department of Cardiology, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - James C Carr
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA
| | - Michael Markl
- Department of Radiology, Cardiovascular Imaging, Northwestern University, Feinberg School of Medicine, Chicago, Illinois, USA.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, Illinois, USA
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Ruh A, Kiselev VG. Larmor frequency dependence on structural anisotropy of magnetically heterogeneous media. J Magn Reson 2019; 307:106584. [PMID: 31476632 DOI: 10.1016/j.jmr.2019.106584] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2019] [Revised: 08/21/2019] [Accepted: 08/22/2019] [Indexed: 06/10/2023]
Abstract
The effect of anisotropic magnetic microstructure on the measurable Larmor frequency offset is investigated in media with heterogeneous magnetic susceptibility using Monte Carlo simulations. The focus is on the transition between the regimes of fast and slow diffusion of NMR-reporting molecules. Simulations demonstrate a perfect agreement with the previously developed analytic theory for fast diffusion. Beyond this regime, the frequency offset shows a pronounced dependence on the medium microarchitecture and the diffusivity of NMR-reporting spins in relation to the magnitude of the susceptibility-induced magnetic field.
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Affiliation(s)
- Alexander Ruh
- Medical Physics, Dept. of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany; Dept. of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, IL, United States
| | - Valerij G Kiselev
- Medical Physics, Dept. of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Germany.
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Berhane H, Ruh A, Husain N, Robinson JD, Rigsby CK, Markl M. Myocardial velocity, intra-, and interventricular dyssynchrony evaluated by tissue phase mapping in pediatric heart transplant recipients. J Magn Reson Imaging 2019; 51:1212-1222. [PMID: 31515865 DOI: 10.1002/jmri.26916] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2019] [Accepted: 08/15/2019] [Indexed: 12/12/2022] Open
Abstract
BACKGROUND Endomyocardial biopsy (EMB) is the standard method for detecting allograft rejection in pediatric heart transplants (Htx). As EMB is invasive and carries a risk of complications, there is a need for a noninvasive alternative for allograft monitoring. PURPOSE To quantify left and right ventricular (LV & RV) peak velocities, velocity twist, and intra-/interventricular dyssynchrony using tissue phase mapping (TPM) in pediatric Htx compared with controls, and to explore the relationship between global cardiac function parameters and the number of rejection episodes to these velocities and intra-/interventricular dyssynchrony. STUDY TYPE Prospective. SUBJECTS Twenty Htx patients (age: 16.0 ± 3.1 years, 11 males) and 18 age- and sex-matched controls (age: 15.5 ± 4.3 years, nine males). FIELD STRENGTH/SEQUENCE 5T; 2D balanced cine steady-state free-precession (bSSFP), TPM (2D cine phase contrast with three-directional velocity encoding). ASSESSMENT LV and RV circumferential, radial, and long-axis velocity-time curves, global and segmental peak velocities were measured using TPM. Short-axis bSSFP images were used to measure global LV and RV function parameters. STATISTICAL TESTS A normality test (Lilliefors test) was performed on all data. For comparisons, a t-test was used for normally distributed data or a Wilcoxon rank-sum test otherwise. Correlations were determined by a Pearson correlation. RESULTS Htx patients had significantly reduced LV (P < 0.05-0.001) and RV (P < 0.05-0.001) systolic and diastolic global and segmental long-axis velocities, reduced RV diastolic peak twist (P < 0.01), and presented with higher interventricular dyssynchrony for long-axis and circumferential motions (P < 0.05-0.001). LV diastolic long-axis dyssynchrony (r = 0.48, P = 0.03) and RV diastolic peak twist (r = -0.64, P = 0.004) significantly correlated with the total number of rejection episodes. DATA CONCLUSION TPM detected differences in biventricular myocardial velocities in pediatric Htx patients compared with controls and indicated a relationship between Htx myocardial velocities and rejection history. LEVEL OF EVIDENCE 2 Technical Efficacy Stage: 3 J. Magn. Reson. Imaging 2020;51:1212-1222.
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Affiliation(s)
- Haben Berhane
- Department of Medical Imaging, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA
| | - Alexander Ruh
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Nazia Husain
- Department of Pediatrics, Division of Pediatric Cardiology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA.,Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Joshua D Robinson
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Pediatrics, Division of Pediatric Cardiology, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA.,Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Cynthia K Rigsby
- Department of Medical Imaging, Ann & Robert H. Lurie Children's Hospital of Chicago, Chicago, Illinois, USA.,Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Pediatrics, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Michael Markl
- Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA.,Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Chicago, Illinois, USA
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Ferrazzi G, Bassenge JP, Wink C, Ruh A, Markl M, Moeller S, Metzger GJ, Ittermann B, Schmitter S. Autocalibrated multiband CAIPIRINHA with through‐time encoding: Proof of principle and application to cardiac tissue phase mapping. Magn Reson Med 2018; 81:1016-1030. [DOI: 10.1002/mrm.27460] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Revised: 06/30/2018] [Accepted: 07/02/2018] [Indexed: 12/27/2022]
Affiliation(s)
- Giulio Ferrazzi
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Jean Pierre Bassenge
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
- Working Group on Cardiovascular Magnetic Resonance, Experimental and Clinical Research Center, a joint cooperation between the Charité Medical Faculty and the Max‐Delbrueck Center for Molecular Medicine
| | - Clarissa Wink
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
| | - Alexander Ruh
- Department of Radiology, Feinberg School of Medicine Northwestern University Chicago Illinois
| | - Michael Markl
- Department of Radiology, Feinberg School of Medicine Northwestern University Chicago Illinois
- Department of Biomedical Engineering, McCormick School of Engineering Northwestern University Chicago Illinois
| | - Steen Moeller
- University of Minnesota, Center for Magnetic Resonance Research (CMRR) Minneapolis Minnesota
| | - Gregory J. Metzger
- University of Minnesota, Center for Magnetic Resonance Research (CMRR) Minneapolis Minnesota
| | - Bernd Ittermann
- Physikalisch‐Technische Bundesanstalt (PTB) Braunschweig and Berlin Germany
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Ruh A, Scherer H, Kiselev VG. The larmor frequency shift in magnetically heterogeneous media depends on their mesoscopic structure. Magn Reson Med 2017; 79:1101-1110. [PMID: 28524556 DOI: 10.1002/mrm.26753] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/19/2017] [Accepted: 04/20/2017] [Indexed: 11/08/2022]
Abstract
PURPOSE Recent studies have addressed the determination of the NMR precession frequency in biological tissues containing magnetic susceptibility differences between cell types. The purpose of this study is to investigate the dependence of the precession frequency on medium microstructure using a simple physical model. THEORY This dependence is governed by diffusion of NMR-visible molecules in magnetically heterogeneous microenvironments. In the limit of fast diffusion, the precession frequency is determined by the average susceptibility-induced magnetic field, whereas in the limit of slow diffusion it is determined by the average local phase factor of precessing spins. METHODS The main method used is Monte Carlo simulation of isotropic suspensions of impermeable magnetized spheres. In addition, NMR spectroscopy was performed in aqueous suspensions of polystyrene microbeads. RESULTS The precession frequency depends on the structural organization of magnetized objects in the medium. Monte Carlo simulations demonstrated a nonmonotonic transition between the regimes of fast and slow diffusion. NMR experiments confirmed the transition, but were unable to confirm its precise form. Results for a given pattern of structural organization obey a scaling law. CONCLUSION The NMR precession frequency exhibits a complex dependence on medium structure. Our results suggest that the commonly assumed limit of fast water diffusion holds for biological tissues with small cells. Magn Reson Med 79:1101-1110, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Alexander Ruh
- Medical Physics, Department of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Harald Scherer
- Institute of Inorganic and Analytical Chemistry, University of Freiburg, Freiburg, Germany
| | - Valerij G Kiselev
- Medical Physics, Department of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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