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Loai S, Qiang B, Laflamme MA, Cheng HLM. Blood-pool MRI assessment of myocardial microvascular reactivity. Front Cardiovasc Med 2023; 10:1216587. [PMID: 38028477 PMCID: PMC10646425 DOI: 10.3389/fcvm.2023.1216587] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2023] [Accepted: 10/20/2023] [Indexed: 12/01/2023] Open
Abstract
Purpose The ability to non-invasively image myocardial microvascular dilation and constriction is essential to assessing intact function and dysfunction. Yet, conventional measurements based on blood oxygenation are not specific to changes in blood volume. The purpose of this study was to extend to the heart a blood-pool MRI approach for assessing vasomodulation in the presence of blood gas changes and investigate if sex-related differences exist. Methods Animals [five male and five female healthy Sprague Dawley rats (200-500 g)] were intubated, ventilated, and cycled through room air (normoxia) and hypercapnia (10% CO2) in 10-minute cycles after i.v. injection of blood-pool agent Ablavar (0.3 mmol/kg). Pre-contrast T1 maps and T1-weighted 3D CINE were acquired on a 3 Tesla preclinical MRI scanner, followed by repeated 3D CINE every 5 min until the end of the gas regime. Invasive laser Doppler flowmetry of myocardial perfusion was performed to corroborate MRI results. Results Myocardial microvascular dilation to hypercapnia and constriction to normoxia were readily visualized on T1 maps. Over 10 min of hypercapnia, female myocardial T1 reduced by 20% (vasodilation), while no significant change was observed in the male myocardium. After return to normoxia, myocardial T1 increased (vasoconstriction) in both sexes (18% in females and 16% in males). Laser Doppler perfusion measurements confirmed vasomodulatory responses observed on MRI. Conclusion Blood-pool MRI is sensitive and specific to vasomodulation in the myocardial microcirculation. Sex-related differences exist in the healthy myocardium in response to mild hypercapnic stimuli.
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Affiliation(s)
- Sadi Loai
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
- Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, Canada
| | - Beiping Qiang
- McEwen Stem Cell Institute, University Health Network, Toronto, ON, Canada
| | - Michael A. Laflamme
- McEwen Stem Cell Institute, University Health Network, Toronto, ON, Canada
- Peter Munk Cardiac Centre, University Health Network, Toronto, ON, Canada
- Laboratory of Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
| | - Hai-Ling Margaret Cheng
- Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
- Translational Biology & Engineering Program, Ted Rogers Centre for Heart Research, Toronto, ON, Canada
- The Edward S. Rogers Sr. Department of Electrical and Computer Engineering, University of Toronto, Toronto, ON, Canada
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Colbert CM, Hollowed JJ, Nguyen DN, Duarte-Vogel S, Dahlbom M, Hu P, Nguyen KL. Fractional myocardial blood volume by ferumoxytol-enhanced MRI: Estimation of ischemic burden. Magn Reson Med 2023; 89:1557-1566. [PMID: 36382769 PMCID: PMC10166270 DOI: 10.1002/mrm.29530] [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] [Received: 03/01/2022] [Revised: 10/26/2022] [Accepted: 10/28/2022] [Indexed: 11/18/2022]
Abstract
PURPOSE To investigate model-fitted fractional myocardial blood volume (fMBV) derived from ferumoxytol-enhanced MRI as a measure of myocardial tissue hypoperfusion at rest. METHODS We artificially induced moderate to severe focal coronary stenosis in the left anterior descending artery of 19 swine by percutaneous delivery of a 3D-printed coronary implant. Using the MOLLI pulse sequence, we acquired T1 maps at 3 T after multiple incremental ferumoxytol doses (0.0-4.0 mg/kg). We computed pixel-wise fMBV using a multi-compartmental modeling approach in 19 ischemic swine and 4 healthy swine. RESULTS Ischemic myocardial segments showed a mean MRI-fMBV of 11.72 ± 3.00%, compared with 8.23 ± 2.12% in remote segments and 8.38 ± 2.23% in normal segments. Ischemic segments showed a restricted transvascular water-exchange rate (ki = 15.32 ± 8.69 s-1 ) relative to remote segments (ki = 17.78 [11.60, 26.36] s-1 ). A mixed-effects model found significant difference in fMBV (p = 0.002) and water-exchange rate (p < 0.001) between ischemic and remote myocardial regions after adjusting for biological sex and slice location. Analysis of fMBV as a predictor of impaired myocardial contractility using receiver operating characteristics showed an area under the curve of 0.89 (95% confidence interval [CI] 0.80, 0.95). An MRI-fMBV threshold of 9.60% has a specificity of 90.0% (95% CI 76.3, 97.2) and a sensitivity of 72.5% (95% CI 56.1, 83.4) for prediction of impaired myocardial contractility. CONCLUSIONS Model-fitted fMBV derived from ferumoxytol-enhanced MRI can distinguish regions of ischemia from remote myocardium in a swine model of myocardial hypoperfusion.
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Affiliation(s)
- Caroline M. Colbert
- Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine at UCLA
- Division of Cardiology, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare System
| | - John J. Hollowed
- Division of Cardiology, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare System
| | - Dylan N. Nguyen
- Department of Computer Science and Engineering, Samueli School of Engineering at UCLA
| | - Sandra Duarte-Vogel
- Division of Laboratory Animal Medicine, David Geffen School of Medicine at UCLA
| | - Magnus Dahlbom
- Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine at UCLA
- Ahmanson Translational Theranostics Division, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA
| | - Peng Hu
- Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine at UCLA
- Diagnostic Cardiovascular Imaging Laboratory, Department of Radiological Sciences, David Geffen School of Medicine at UCLA
| | - Kim-Lien Nguyen
- Physics and Biology in Medicine Graduate Program, David Geffen School of Medicine at UCLA
- Division of Cardiology, David Geffen School of Medicine at UCLA and VA Greater Los Angeles Healthcare System
- Diagnostic Cardiovascular Imaging Laboratory, Department of Radiological Sciences, David Geffen School of Medicine at UCLA
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MacMahon E, Brougham DF. pH Dependence of MRI Contrast in Magnetic Nanoparticle Suspensions Demonstrates Inner-Sphere Relaxivity Contributions and Reveals the Mechanism of Dissolution. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:2171-2181. [PMID: 36734523 PMCID: PMC9933532 DOI: 10.1021/acs.langmuir.2c02621] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2022] [Revised: 01/23/2023] [Indexed: 06/18/2023]
Abstract
Superparamagnetic iron oxide nanoparticles, MNPs, are under investigation as stimulus-responsive nanocarriers that can be tracked by magnetic resonance imaging. However, fundamental questions remain, including the effect of differing surface chemistries on MR image contrast efficacy (relaxivity), both initially and over time in the biological environment. The effects of pH and ligand type on the relaxivity of electrostatically and sterically stabilized spherical 8.8 nm superparamagnetic MNP suspensions are described. It is shown for the first time that across the pH ranges, within which the particles are fully dispersed, increasing acidity progressively reduces relaxivity for all ligand types. This effect is stronger for electrostatically (citrate or APTES) than for sterically stabilized (PEG5000) MNPs. NMR relaxation profiles (relaxivity as a function of 1H Larmor frequency) identified an inner-sphere effect, arising from the protonation of bare oxide or low-molecular-weight-bound species, as the cause. The suppression is not accounted for by the accepted model (SPM theory) and is contrary to previous reports of increased relaxivity at lower pH for paramagnetic iron oxide nanoparticles. We propose that the suppression arises from the orientation of water molecules, with the oxygen atom facing the surface increasingly preferred with increasing surface protonation. For APTES-stabilized MNPs, pendant amines and the silane layer confer exceptional chemical and colloidal stability at low pH. Dissolution of these particles at pH 1.8 was monitored over several months by combining in situ measurements of relaxation profiles with dynamic light scattering. It was shown that particles are magnetically intact for extended periods until they rapidly dissolve, once the silane layer is breached, in a process that is apparently second order in particle concentration. The findings are of interest for tracking MNP fate, for quantitation, and for retention of magnetic responsiveness in biological settings.
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Affiliation(s)
- Eoghan MacMahon
- School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
| | - Dermot F. Brougham
- School of Chemistry, University College Dublin, Belfield, Dublin 4, Ireland
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Cheng HLM. Emerging MRI techniques for molecular and functional phenotyping of the diseased heart. Front Cardiovasc Med 2022; 9:1072828. [PMID: 36545017 PMCID: PMC9760746 DOI: 10.3389/fcvm.2022.1072828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 11/22/2022] [Indexed: 12/12/2022] Open
Abstract
Recent advances in cardiac MRI (CMR) capabilities have truly transformed its potential for deep phenotyping of the diseased heart. Long known for its unparalleled soft tissue contrast and excellent depiction of three-dimensional (3D) structure, CMR now boasts a range of unique capabilities for probing disease at the tissue and molecular level. We can look beyond coronary vessel blockages and detect vessel disease not visible on a structural level. We can assess if early fibrotic tissue is being laid down in between viable cardiac muscle cells. We can measure deformation of the heart wall to determine early presentation of stiffening. We can even assess how cardiomyocytes are utilizing energy, where abnormalities are often precursors to overt structural and functional deficits. Finally, with artificial intelligence gaining traction due to the high computing power available today, deep learning has proven itself a viable contender with traditional acceleration techniques for real-time CMR. In this review, we will survey five key emerging MRI techniques that have the potential to transform the CMR clinic and permit early detection and intervention. The emerging areas are: (1) imaging microvascular dysfunction, (2) imaging fibrosis, (3) imaging strain, (4) imaging early metabolic changes, and (5) deep learning for acceleration. Through a concerted effort to develop and translate these areas into the CMR clinic, we are committing ourselves to actualizing early diagnostics for the most intractable heart disease phenotypes.
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Affiliation(s)
- Hai-Ling Margaret Cheng
- The Edward S. Rogers Sr. Department of Electrical & Computer Engineering, Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
- Ted Rogers Centre for Heart Research, Translational Biology & Engineering Program, Toronto, ON, Canada
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Tian X, Ruan L, Zhou S, Wu L, Cao J, Qi X, Zhang X, Shen S. Appropriate Size of Fe 3O 4 Nanoparticles for Cancer Therapy by Ferroptosis. ACS APPLIED BIO MATERIALS 2022; 5:1692-1699. [PMID: 35297253 DOI: 10.1021/acsabm.2c00068] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Iron oxide nanoparticles can induce cell death due to the ferroptosis mechanism, showing a great potential for cancer therapy. Here, we synthesized different-sized iron oxide nanoparticles (2-100 nm) to investigate their antitumor effect and toxicity mechanism. It was found that ultrasmall nanoparticles (< ∼5 nm) could accumulate in nucleus and were more efficient in triggering the generation of •OH than larger nanoparticles due to the quicker release of Fe2+, thus exhibiting more remarkable cytotoxicity. Nevertheless, 10 nm iron oxide nanoparticles group displayed the best antitumor effect in vivo. We studied the in vivo and intratumoral biodistribution of the nanoparticles and found that the therapeutic effects were related to both the tumoral accumulation and intratumoral distribution of nanoparticles. This work indicates the appropriate size of Fe3O4 NPs for cancer treatment and illustrates the possible factors that influence the therapeutic effect, suggesting the great potential of iron oxide in clinical application.
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Affiliation(s)
- Xiangrong Tian
- Affiliated Hospital of Jiangsu University, 438 Jiefang Road, Zhenjiang, Jiangsu 212001, China.,College of Pharmaceutical Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Li Ruan
- Affiliated Hospital of Jiangsu University, 438 Jiefang Road, Zhenjiang, Jiangsu 212001, China.,College of Pharmaceutical Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Shengwang Zhou
- College of Pharmaceutical Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Lin Wu
- Affiliated Hospital of Jiangsu University, 438 Jiefang Road, Zhenjiang, Jiangsu 212001, China
| | - Jin Cao
- College of Pharmaceutical Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Xueyong Qi
- College of Pharmaceutical Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
| | - Xin Zhang
- Affiliated Hospital of Jiangsu University, 438 Jiefang Road, Zhenjiang, Jiangsu 212001, China
| | - Song Shen
- College of Pharmaceutical Sciences, Jiangsu University, 301 Xuefu Road, Zhenjiang, Jiangsu 212013, China
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Weyers JJ, Ramanan V, Javed A, Barry J, Larsen M, Nayak K, Wright GA, Ghugre NR. Myocardial blood flow is the dominant factor influencing cardiac magnetic resonance adenosine stress T2. NMR IN BIOMEDICINE 2022; 35:e4643. [PMID: 34791720 PMCID: PMC8828684 DOI: 10.1002/nbm.4643] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 09/24/2021] [Accepted: 10/10/2021] [Indexed: 06/02/2023]
Abstract
Stress imaging identifies ischemic myocardium by comparing hemodynamics during rest and hyperemic stress. Hyperemia affects multiple hemodynamic parameters in myocardium, including myocardial blood flow (MBF), myocardial blood volume (MBV), and venous blood oxygen levels (PvO2 ). Cardiac T2 is sensitive to these changes and therefore is a promising non-contrast option for stress imaging; however, the impact of individual hemodynamic factors on T2 is poorly understood, making the connection from altered T2 to changes within the tissue difficult. To better understand this interplay, we performed T2 mapping and measured various hemodynamic factors independently in healthy pigs at multiple levels of hyperemic stress, induced by different doses of adenosine (0.14-0.56 mg/kg/min). T1 mapping quantified changes in MBV. MBF was assessed with microspheres, and oxygen consumption was determined by the rate pressure product (RPP). Simulations were also run to better characterize individual contributions to T2. Myocardial T2, MBF, oxygen consumption, and MBV all changed to varying extents between each level of adenosine stress (T2 = 37.6-41.8 ms; MBF = 0.48-1.32 mL/min/g; RPP = 6507-4001 bmp*mmHg; maximum percent change in MBV = 1.31%). Multivariable analyses revealed MBF as the dominant influence on T2 during hyperemia (significant β-values >7). Myocardial oxygen consumption had almost no effect on T2 (β-values <0.002); since PvO2 is influenced by both oxygen consumption and MBF, PvO2 changes detected by T2 during adenosine stress can be attributed to MBF. Simulations varying PvO2 and MBV confirmed that PvO2 had the strongest influence on T2, but MBV became important at high PvO2 . Together, these data suggest a model where, during adenosine stress, myocardial T2 responds predominantly to changes in MBF, but at high hyperemia MBV is also influential. Thus, changes in adenosine stress T2 can now be interpreted in terms of the physiological changes that led to it, enabling T2 mapping to become a viable non-contrast option to detect ischemic myocardial tissue.
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Affiliation(s)
- Jill J Weyers
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Venkat Ramanan
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Ahsan Javed
- Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California
| | - Jennifer Barry
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Melissa Larsen
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
| | - Krishna Nayak
- Ming Hsieh Department of Electrical Engineering, University of Southern California, Los Angeles, California
| | - Graham A Wright
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
- Schulich Heart Research Program, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - Nilesh R Ghugre
- Physical Sciences Platform, Sunnybrook Research Institute, Toronto, Ontario, Canada
- Schulich Heart Research Program, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
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