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Bustin A, Witschey WRT, van Heeswijk RB, Cochet H, Stuber M. Magnetic resonance myocardial T1ρ mapping : Technical overview, challenges, emerging developments, and clinical applications. J Cardiovasc Magn Reson 2023; 25:34. [PMID: 37331930 DOI: 10.1186/s12968-023-00940-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 05/15/2023] [Indexed: 06/20/2023] Open
Abstract
The potential of cardiac magnetic resonance to improve cardiovascular care and patient management is considerable. Myocardial T1-rho (T1ρ) mapping, in particular, has emerged as a promising biomarker for quantifying myocardial injuries without exogenous contrast agents. Its potential as a contrast-agent-free ("needle-free") and cost-effective diagnostic marker promises high impact both in terms of clinical outcomes and patient comfort. However, myocardial T1ρ mapping is still at a nascent stage of development and the evidence supporting its diagnostic performance and clinical effectiveness is scant, though likely to change with technological improvements. The present review aims at providing a primer on the essentials of myocardial T1ρ mapping, and to describe the current range of clinical applications of the technique to detect and quantify myocardial injuries. We also delineate the important limitations and challenges for clinical deployment, including the urgent need for standardization, the evaluation of bias, and the critical importance of clinical testing. We conclude by outlining technical developments to be expected in the future. If needle-free myocardial T1ρ mapping is shown to improve patient diagnosis and prognosis, and can be effectively integrated in cardiovascular practice, it will fulfill its potential as an essential component of a cardiac magnetic resonance examination.
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Affiliation(s)
- Aurelien Bustin
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, Université de Bordeaux, INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Avenue du Haut Lévêque, 33604, Pessac, France.
- Department of Cardiovascular Imaging, Hôpital Cardiologique du Haut-Lévêque, CHU de Bordeaux, Avenue de Magellan, 33604, Pessac, France.
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.
| | | | - Ruud B van Heeswijk
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
| | - Hubert Cochet
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, Université de Bordeaux, INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Avenue du Haut Lévêque, 33604, Pessac, France
- Department of Cardiovascular Imaging, Hôpital Cardiologique du Haut-Lévêque, CHU de Bordeaux, Avenue de Magellan, 33604, Pessac, France
| | - Matthias Stuber
- IHU LIRYC, Electrophysiology and Heart Modeling Institute, Université de Bordeaux, INSERM, Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Avenue du Haut Lévêque, 33604, Pessac, France
- Department of Diagnostic and Interventional Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland
- Center for Biomedical Imaging (CIBM), Lausanne, Switzerland
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Tolkkinen K, Mailhiot SE, Selent A, Mankinen O, Henschel H, Nieminen MT, Hanni M, Kantola AM, Liimatainen T, Telkki VV. SPICY: a method for single scan rotating frame relaxometry. Phys Chem Chem Phys 2023; 25:13164-13169. [PMID: 37129427 PMCID: PMC10171246 DOI: 10.1039/d2cp05988f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
T 1ρ is an NMR relaxation mode that is sensitive to low frequency molecular motions, making it an especially valuable tool in biomolecular research. Here, we introduce a new method, SPICY, for measuring T1ρ relaxation times. In contrast to conventional T1ρ experiments, in which the sequence is repeated many times to determine the T1ρ time, the SPICY sequence allows determination of T1ρ within a single scan, shortening the experiment time remarkably. We demonstrate the method using 1H T1ρ relaxation dispersion experiments. Additionally, we combine the sequence with spatial encoding to produce 1D images in a single scan. We show that T1ρ relaxation times obtained using the single scan approach are in good agreement with those obtained using the traditional experiments.
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Affiliation(s)
| | | | - Anne Selent
- NMR Research Unit, University of Oulu, Oulu, Finland.
| | - Otto Mankinen
- NMR Research Unit, University of Oulu, Oulu, Finland.
| | - Henning Henschel
- Department of Medicinal Chemistry, Uppsala University, Uppsala, Sweden
| | - Miika T Nieminen
- Research Unit of Health Sciences and Technology, University of Oulu, Oulu, Finland
- Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
| | - Matti Hanni
- Research Unit of Health Sciences and Technology, University of Oulu, Oulu, Finland
- Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
| | - Anu M Kantola
- NMR Research Unit, University of Oulu, Oulu, Finland.
| | - Timo Liimatainen
- Research Unit of Health Sciences and Technology, University of Oulu, Oulu, Finland
- Department of Diagnostic Radiology, Oulu University Hospital, Oulu, Finland
- Medical Research Center Oulu, University of Oulu and Oulu University Hospital, Oulu, Finland
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Saito S. [5. Advanced Imaging Technology-T1rho-CEST Imaging]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2022; 78:95-100. [PMID: 35046227 DOI: 10.6009/jjrt.780111] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Shigeyoshi Saito
- Laboratory of Advanced Imaging Technology, Department of Medical Physics and Engineering, Division of Health Sciences, Osaka University Graduate School of Medicine.,Department of Advanced Medical Technology, National Cardiovascular and Cerebral Research Center
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4
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Johnson CP, Thedens DR, Kruger SJ, Magnotta VA. Three-Dimensional GRE T 1ρ mapping of the brain using tailored variable flip-angle scheduling. Magn Reson Med 2020; 84:1235-1249. [PMID: 32052489 DOI: 10.1002/mrm.28198] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2019] [Revised: 01/07/2020] [Accepted: 01/13/2020] [Indexed: 12/26/2022]
Abstract
PURPOSE To introduce a new approach called tailored variable flip-angle (VFA) scheduling for SNR-efficient 3D T1ρ mapping of the brain using a magnetization-prepared gradient-echo sequence. METHODS Simulations were used to assess the relative SNR efficiency, quantitative accuracy, and spatial blurring of tailored VFA scheduling for T1ρ mapping of brain tissue compared with magnetization-prepared angle-modulated partitioned k-space spoiled gradient-echo snapshots (MAPSS), a state-of-the-art technique for accurate 3D gradient-echo T1ρ mapping. Simulations were also used to calculate optimal imaging parameters for tailored VFA scheduling versus MAPSS, without and with nulling of CSF. Four participants were imaged at 3T MRI to demonstrate the feasibility of tailored VFA scheduling for T1ρ mapping of the brain. Using MAPSS as a reference standard, in vivo data were used to validate the relative SNR efficiency and quantitative accuracy of the new approach. RESULTS Tailored VFA scheduling can provide a 2-fold to 4-fold gain in the SNR of the resulting T1ρ map as compared with MAPSS when using identical sequence parameters while limiting T1ρ quantification errors to 2% or less. In vivo whole-brain 3D T1ρ maps acquired with tailored VFA scheduling had superior SNR efficiency than is achievable with MAPSS, and the SNR efficiency improved with a greater number of views per segment. CONCLUSIONS Tailored VFA scheduling is an SNR-efficient GRE technique for 3D T1ρ mapping of the brain that provides increased flexibility in choice of imaging parameters compared with MAPSS, which may benefit a variety of applications.
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Affiliation(s)
- Casey P Johnson
- Veterinary Clinical Sciences Department, University of Minnesota, Saint Paul, MN, USA.,Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | | | | | - Vincent A Magnotta
- Department of Radiology, University of Iowa, Iowa City, IA, USA.,Department of Psychiatry, University of Iowa, Iowa City, IA, USA.,Department of Biomedical Engineering, University of Iowa, Iowa City, IA, USA
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5
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Ali SO, Fessas P, Kaggie JD, Zaccagna F, Houston G, Reid S, Graves MJ, Gallagher FA. Evaluation of the sensitivity of R 1ρ MRI to pH and macromolecular density. Magn Reson Imaging 2019; 58:156-161. [PMID: 30771445 PMCID: PMC6422633 DOI: 10.1016/j.mri.2019.02.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 02/12/2019] [Accepted: 02/13/2019] [Indexed: 11/17/2022]
Abstract
The tumor microenvironment is characteristically acidic and this extracellular acidosis is known to play a role in carcinogenesis and metastasis and can affect tumor chemosensitivity and radiosensitivity. Intracellular pH has been used as a possible biomarker of salvageable tissue in ischemic stroke. A non-invasive MRI-based approach for the determination and imaging of cerebral pH would be a powerful tool in cancer diagnosis and monitoring, as well as stroke treatment planning. Several pH-based MRI imaging approaches have been proposed but for these to be useful, disentangling the effects of pH from other parameters which may affect the measured MRI signal is crucial to ensure accuracy and specificity. R1 relaxation in the rotating frame (R1ρ) is an example of a method that has been proposed to probe pH in vivo using MRI. In this study, we have investigated the relationship between R1ρ, pH, and macromolecular density in vitro using phantoms and in human volunteers. Here we show that the rate of R1ρ relaxation (=1/T1ρ) varies with pH but only in the presence of macromolecules. At constant pH, phantom macromolecular density inversely correlated with R1ρ. R1ρ imaging of the normal human brain demonstrated regional heterogeneity with significant differences between structurally distinct regions, which are likely to be independent of pH. For example, R1ρ was higher in the basal ganglia compared to grey matter and higher in grey matter compared to white matter. We conclude that R1ρ cannot be reliably used to image tissue pH without deconvolution from the effects of local tissue macromolecular composition.
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Affiliation(s)
- Syed O Ali
- University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Hills Rd, Cambridge CB2 0SP, United Kingdom
| | - Petros Fessas
- University of Cambridge School of Clinical Medicine, Addenbrooke's Hospital, Hills Rd, Cambridge CB2 0SP, United Kingdom
| | - Joshua D Kaggie
- Department of Radiology, Box 218, University of Cambridge, Cambridge CB2 0QQ, United Kingdom; Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, United Kingdom, CB2 0QQ.
| | - Fulvio Zaccagna
- Department of Radiology, Box 218, University of Cambridge, Cambridge CB2 0QQ, United Kingdom; Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, United Kingdom, CB2 0QQ
| | | | - Scott Reid
- GE Healthcare, Amersham, United Kingdom, HP7 9JQ
| | - Martin J Graves
- Department of Radiology, Box 218, University of Cambridge, Cambridge CB2 0QQ, United Kingdom; Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, United Kingdom, CB2 0QQ
| | - Ferdia A Gallagher
- Department of Radiology, Box 218, University of Cambridge, Cambridge CB2 0QQ, United Kingdom; Cambridge University Hospitals NHS Foundation Trust, Addenbrooke's Hospital, Cambridge, United Kingdom, CB2 0QQ.
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Zu Z, Afzal A, Li H, Xie J, Gore JC. Spin-lock imaging of early tissue pH changes in ischemic rat brain. NMR IN BIOMEDICINE 2018; 31:e3893. [PMID: 29424463 PMCID: PMC5854549 DOI: 10.1002/nbm.3893] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 11/23/2017] [Accepted: 12/07/2017] [Indexed: 05/03/2023]
Abstract
We have previously reported that the dispersion of spin-lattice relaxation rates in the rotating frame (R1ρ ) of tissue water protons at high field can be dominated by chemical exchange contributions. Ischemia in brain causes changes in tissue pH, which in turn may affect proton exchange rates. Amide proton transfer (APT, a form of chemical exchange saturation transfer) has been shown to be sensitive to chemical exchange rates and able to detect pH changes non-invasively following ischemic stroke. However, the specificity of APT to pH changes is decreased because of the influence of several other factors that affect magnetization transfer. R1ρ is less influenced by such confounding factors and thus may be more specific for detecting variations in pH. Here, we applied a spin-locking sequence to detect ischemic stroke in animal models. Although R1ρ images acquired with a single spin-locking amplitude (ω1 ) have previously been used to assess stroke, here we use ΔR1ρ , which is the difference in R1ρ values acquired with two different locking fields to emphasize selectively the contribution of chemical exchange effects. Numerical simulations with different exchange rates and measurements of tissue homogenates with different pH were performed to evaluate the specificity of ΔR1ρ to detect tissue acidosis. Spin-lock and APT data were acquired on five rat brains after ischemic strokes induced via middle cerebral artery occlusions. Correlations between these data were analyzed at different time points after the onset of stroke. The results show that ΔR1ρ (but not R1ρ acquired with a single ω1 ) was significantly correlated with APT metrics consistent with ΔR1ρ varying with pH.
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Affiliation(s)
- Zhongliang Zu
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Aqeela Afzal
- Department of Neurological Surgery, Vanderbilt University, Nashville, Tennessee, USA
| | - Hua Li
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - Jingping Xie
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
| | - John C. Gore
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA
- Department of Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA
- Deparment of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
- Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee, USA
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Khan MA, Laakso H, Laidinen S, Kettunen S, Heikura T, Ylä-Herttuala S, Liimatainen T. The follow-up of progressive hypertrophic cardiomyopathy using magnetic resonance rotating frame relaxation times. NMR IN BIOMEDICINE 2018; 31:e3871. [PMID: 29244217 DOI: 10.1002/nbm.3871] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2017] [Revised: 10/20/2017] [Accepted: 10/29/2017] [Indexed: 06/07/2023]
Abstract
Magnetic resonance rotating frame relaxation times are an alternative non-contrast agent choice for the diagnosis of chronic myocardial infarct. Fibrosis typically occurs in progressive hypertrophic cardiomyopathy. Fibrosis has been imaged in myocardial infarcted tissue using rotating frame relaxation times, which provides the possibility to follow up progressive cardiomyopathy without contrast agents. Mild and severe left ventricular hypertrophy were induced in mice by transverse aortic constriction, and the longitudinal rotating frame relaxation times (T1ρ ) and relaxation along the fictitious field (TRAFF2 , TRAFF3 ) were measured at 5, 10, 24, 62 and 89 days after transverse aortic constriction in vivo. Myocardial fibrosis was verified using Masson's trichrome staining. Increases in the relative relaxation time differences of T1ρ , together with TRAFF2 and TRAFF3 , between fibrotic and remote tissues over time were observed. Furthermore, TRAFF2 and TRAFF3 showed higher relaxation times overall in fibrotic tissue than T1ρ . Relaxation time differences were highly correlated with an excess of histologically verified fibrosis. We found that TRAFF2 and TRAFF3 are more sensitive than T1ρ to hypertrophic cardiomyopathy-related tissue changes and can serve as non-invasive diagnostic magnetic resonance imaging markers to follow up the mouse model of progressive hypertrophic cardiomyopathy.
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Affiliation(s)
- Muhammad Arsalan Khan
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Hanne Laakso
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, MN, USA
| | - Svetlana Laidinen
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Sanna Kettunen
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Tommi Heikura
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
| | - Seppo Ylä-Herttuala
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
- Heart Center, Kuopio University Hospital, Kuopio, Finland
| | - Timo Liimatainen
- Department of Biotechnology and Molecular Medicine, A.I. Virtanen Institute for Molecular Sciences, University of Eastern Finland, Kuopio, Finland
- Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland
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Spear JT, Gore JC. New insights into rotating frame relaxation at high field. NMR IN BIOMEDICINE 2016; 29:1258-73. [PMID: 26866422 PMCID: PMC6935321 DOI: 10.1002/nbm.3490] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Revised: 12/07/2015] [Accepted: 12/30/2015] [Indexed: 05/03/2023]
Abstract
Measurements of spin-lock relaxation rates in the rotating frame (R1ρ ) at high magnetic fields afford the ability to probe not only relatively slow molecular motions, but also other dynamic processes, such as chemical exchange and diffusion. In particular, measurements of the variation (or dispersion) of R1ρ with locking field allow the derivation of quantitative parameters that describe these processes. Measurements in deuterated solutions demonstrate the manner and degree to which exchange dominates relaxation at high fields (4.7 T, 7 T) in simple solutions, whereas temperature and pH are shown to be very influential factors affecting the rates of proton exchange. Simulations and experiments show that multiple exchanging pools of protons in realistic tissues can be assumed to behave independently of each other. R1ρ measurements can be combined to derive an exchange rate contrast (ERC) that produces images whose intensities emphasize protons with specific exchange rates rather than chemical shifts. In addition, water diffusion in the presence of intrinsic susceptibility gradients may produce significant effects on R1ρ dispersions at high fields. The exchange and diffusion effects act independently of each other, as confirmed by simulation and experimentally in studies of red blood cells at different levels of oxygenation. Collectively, R1ρ measurements provide an ability to quantify exchange processes, to provide images that depict protons with specific exchange rates and to describe the microstructure of tissues containing magnetic inhomogeneities. As such, they complement traditional T1 or T2 measurements and provide additional insights from measurements of R1ρ at a single locking field. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- John T. Spear
- Correspondence to: J. T. Spear, Physics and Astronomy, Vanderbilt University Institute of Imaging Science, Nashville, TN 37232, USA.
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Gilani IA, Sepponen R. Quantitative rotating frame relaxometry methods in MRI. NMR IN BIOMEDICINE 2016; 29:841-861. [PMID: 27100142 DOI: 10.1002/nbm.3518] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Revised: 01/21/2016] [Accepted: 02/18/2016] [Indexed: 06/05/2023]
Abstract
Macromolecular degeneration and biochemical changes in tissue can be quantified using rotating frame relaxometry in MRI. It has been shown in several studies that the rotating frame longitudinal relaxation rate constant (R1ρ ) and the rotating frame transverse relaxation rate constant (R2ρ ) are sensitive biomarkers of phenomena at the cellular level. In this comprehensive review, existing MRI methods for probing the biophysical mechanisms that affect the rotating frame relaxation rates of the tissue (i.e. R1ρ and R2ρ ) are presented. Long acquisition times and high radiofrequency (RF) energy deposition into tissue during the process of spin-locking in rotating frame relaxometry are the major barriers to the establishment of these relaxation contrasts at high magnetic fields. Therefore, clinical applications of R1ρ and R2ρ MRI using on- or off-resonance RF excitation methods remain challenging. Accordingly, this review describes the theoretical and experimental approaches to the design of hard RF pulse cluster- and adiabatic RF pulse-based excitation schemes for accurate and precise measurements of R1ρ and R2ρ . The merits and drawbacks of different MRI acquisition strategies for quantitative relaxation rate measurement in the rotating frame regime are reviewed. In addition, this review summarizes current clinical applications of rotating frame MRI sequences. Copyright © 2016 John Wiley & Sons, Ltd.
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Affiliation(s)
- Irtiza Ali Gilani
- Brain Research Unit, Department of Neuroscience and Biomedical Engineering, Aalto University, Aalto, Finland
- Advanced Magnetic Imaging Center, Aalto University, Aalto, Finland
- National Magnetic Resonance Research Center (UMRAM), Bilkent University, Ankara, Turkey
| | - Raimo Sepponen
- Department of Electronics, School of Electrical Engineering, Aalto University, Aalto, Finland
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Endogenous contrast T1rho cardiac magnetic resonance for myocardial fibrosis in hypertrophic cardiomyopathy patients. J Cardiol 2015; 66:520-6. [PMID: 25981868 DOI: 10.1016/j.jjcc.2015.03.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2014] [Revised: 02/16/2015] [Accepted: 03/02/2015] [Indexed: 02/05/2023]
Abstract
BACKGROUND Late gadolinium enhancement (LGE) is a standard method to evaluate myocardial fibrosis, but restricted due to contrast agent contraindications. Non-contrast T1rho can generate endogenous contrast, and detect fibrosis in chronic myocardial infarction. However, T1rho for hypertrophic cardiomyopathy (HCM) patients is still unreported. The present study aimed to investigate T1rho for fibrotic assessment and the clinical implication in HCM patients. METHODS 18 HCM patients and 8 controls underwent T1rho, cine, and LGE cardiac magnetic resonance (CMR). T1rho relaxation time maps were created. Left ventricular (LV) parameters assessed included wall thickness, wall thickening, chamber volumes, ejection function, and fibrotic size. New York Heart Association (NYHA) functional classification was conducted. RESULTS Hyper-T1rho value was identified in 12 HCM patients, consistent with LGE. The mean T1rho values of controls, LGE-negative patients, and remote myocardium of LGE-positive patients were 42.2±1.6ms, 43.9±2.5ms, and 42.5±1.2ms respectively, and these values showed no significant difference (all p>0.05). T1rho-3-SD and T1rho-4-SD fibrotic sizes (32.5±14.0% and 25.1±11.5%) did not differ from LGE fibrotic size (28.1±11.2%) (both p>0.05). For the fibrotic size, T1rho-3-SD method obtained the strongest correlation with LGE (r=0.88, p<0.001), and T1rho-4-SD obtained the minimal mean difference with LGE (-3.1%; -15.2 to 9.1%), compared with other SDs. All the fibrotic sizes assessed by both methods correlated directly with LV maximal end-diastolic thickness (all p<0.05). Negative correlation was found between T1rho-4-SD fibrotic size and LV ejection fraction (r=-0.49, p=0.11). T1rho-4-SD fibrotic size showed positive correlation with NYHA class (r=0.46, p=0.13). CONCLUSIONS T1rho CMR has potential to detect fibrosis in HCM patients. 4-SD may be the appropriate threshold for assessment.
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12
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Kauppinen RA. Multiparametric magnetic resonance imaging of acute experimental brain ischaemia. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2014; 80:12-25. [PMID: 24924265 DOI: 10.1016/j.pnmrs.2014.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 05/07/2014] [Accepted: 05/07/2014] [Indexed: 06/03/2023]
Abstract
Ischaemia is a condition in which blood flow either drops to zero or proceeds at severely decreased levels that cannot supply sufficient oxidizable substrates to maintain energy metabolism in vivo. Brain, a highly oxidative organ, is particularly susceptible to ischaemia. Ischaemia leads to loss of consciousness in seconds and, if prolonged, permanent tissue damage is inevitable. Ischaemia primarily results in a collapse of cerebral energy state, followed by a series of subtle changes in anaerobic metabolism, ion and water homeostasis that eventually initiate destructive internal and external processes in brain tissue. (31)P and (1)H NMR spectroscopy were initially used to evaluate anaerobic metabolism in brain. However, since the early 1990s (1)H Magnetic Resonance Imaging (MRI), exploiting the nuclear magnetism of tissue water, has become the key method for assessment of ischaemic brain tissue. This article summarises multi-parametric (1)H MRI work that has exploited diffusion, relaxation and magnetisation transfer as 'contrasts' to image ischaemic brain in preclinical models for the first few hours, with a view to assessing evolution of ischaemia and tissue viability in a non-invasive manner.
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Affiliation(s)
- Risto A Kauppinen
- School of Experimental Psychology and Clinical Research and Imaging Centre, University of Bristol, 12a Priory Road, Bristol BS8 1TU, UK.
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Autio JA, Shatillo A, Giniatullin R, Gröhn OH. Parenchymal spin-lock fMRI signals associated with cortical spreading depression. J Cereb Blood Flow Metab 2014; 34:768-75. [PMID: 24496172 PMCID: PMC4013757 DOI: 10.1038/jcbfm.2014.16] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Revised: 12/30/2013] [Accepted: 01/08/2014] [Indexed: 01/30/2023]
Abstract
We found novel types of parenchymal functional magnetic resonance imaging (fMRI) signals in the rat brain during large increases in metabolism. Cortical spreading depression (CSD), a self-propagating wave of cellular activation, is associated with several pathologic conditions such as migraine and stroke. It was used as a paradigm to evoke transient neuronal depolarization leading to enhanced energy consumption. Activation of CSD was investigated using spin-lock (SL), diffusion, blood oxygenation level-dependent and cerebral blood volume fMRI techniques. Our results show that the SL-fMRI signal is generated by endogenous parenchymal mechanisms during CSD propagation, and these mechanisms are not associated with hemodynamic changes or cellular swelling. Protein phantoms suggest that pH change alone does not explain the observed SL-fMRI signal changes. However, increased amounts of inorganic phosphates released from high-energy phosphates combined with pH changes may produce SL- power-dependent longitudinal relaxation in the rotating frame (R₁ρ) changes in protein phantoms that are similar to those observed during CSD, as seen before in acute ischemia under our experimental conditions. This links SL-fMRI changes intimately to energy metabolism and supports the use of the SL technique as a new, promising functional approach for noninvasive imaging of metabolic transitions in the active or pathologic brain.
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Affiliation(s)
- Joonas A Autio
- 1] Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland [2] Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
| | - Artem Shatillo
- Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland
| | - Rashid Giniatullin
- Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland
| | - Olli H Gröhn
- Department of Neurobiology, A. I. Virtanen Institute, University of Eastern Finland, Kuopio, Finland
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Evaluation of activity-dependent functional pH and T1ρ response in the visual cortex. Neuroimage 2014; 95:336-43. [PMID: 24486980 DOI: 10.1016/j.neuroimage.2014.01.042] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 01/21/2014] [Accepted: 01/24/2014] [Indexed: 01/16/2023] Open
Abstract
Recent experiments suggest that T1 relaxation in the rotating frame (T1ρ) detects localized metabolic changes in the human visual cortex induced by a flashing checkerboard task. Possible sources of the T1ρ signal include pH, glucose, and glutamate concentrations as well as changes in cerebral blood volume. In this study we explored the relationship of the T1ρ signal changes related to cerebral blood volume changes by employing inferior saturation pulses. Our hypothesis was that there would be a contribution of cerebral blood volume to the functional T1ρ signal, but a majority of the signal would correspond to metabolic changes. In addition, the relationship between T1ρ and pH was explored by manipulating the frequency of the flashing checkerboard and imaging with T1ρ, BOLD, and (31)P spectroscopy. We hypothesized that T1ρ and pH changes would be sensitive to the stimulation frequency. To test this hypothesis, we used a full-field visual flashing checkerboard and varied the frequency between 1, 4, and 7Hz. Supporting our hypotheses, we found that approximately 73% of the measured signal change corresponds to metabolism in vivo and that increasing stimulation frequency increased responses measured by all three imaging modalities. The activation area detected by T1ρ overlapped to a large degree with that detected by BOLD, although the T1ρ response area was significantly smaller. (31)P spectroscopy detected a greater acidosis with the higher stimulation frequencies. These observations suggest that, similar to the BOLD response, the magnitude of the T1ρ and pH response depends on stimulation frequency and is thus likely to be activity-dependent.
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Watts R, Andrews T, Hipko S, Gonyea JV, Filippi CG. In vivo whole-brain T1-rho mapping across adulthood: Normative values and age dependence. J Magn Reson Imaging 2013; 40:376-82. [DOI: 10.1002/jmri.24358] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Accepted: 07/31/2013] [Indexed: 11/08/2022] Open
Affiliation(s)
- Richard Watts
- UVM MRI Center for Biomedical Imaging; University of Vermont College of Medicine; Burlington Vermont USA
- Department of Radiology; Fletcher-Allen Healthcare; Burlington Vermont USA
| | - Trevor Andrews
- UVM MRI Center for Biomedical Imaging; University of Vermont College of Medicine; Burlington Vermont USA
- Department of Radiology; Fletcher-Allen Healthcare; Burlington Vermont USA
- Philips Healthcare; Cleveland Ohio USA
| | - Scott Hipko
- UVM MRI Center for Biomedical Imaging; University of Vermont College of Medicine; Burlington Vermont USA
| | - Jay V. Gonyea
- UVM MRI Center for Biomedical Imaging; University of Vermont College of Medicine; Burlington Vermont USA
| | - Christopher G. Filippi
- UVM MRI Center for Biomedical Imaging; University of Vermont College of Medicine; Burlington Vermont USA
- Department of Radiology; Fletcher-Allen Healthcare; Burlington Vermont USA
- Department of Neurology; Fletcher-Allen Healthcare; Burlington Vermont USA
- Department of Radiology; Columbia University Medical Center; New York USA
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Jin T, Kim SG. Characterization of non-hemodynamic functional signal measured by spin-lock fMRI. Neuroimage 2013; 78:385-95. [PMID: 23618601 DOI: 10.1016/j.neuroimage.2013.04.045] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 04/03/2013] [Accepted: 04/12/2013] [Indexed: 01/29/2023] Open
Abstract
Current functional MRI techniques measure hemodynamic changes induced by neural activity. Alternative measurement of signals originated from tissue is desirable and may be achieved using T1ρ, the spin-lattice relaxation time in the rotating-frame, which is measured by spin-lock MRI. Functional T1ρ changes in the brain can have contributions from vascular dilation, tissue acidosis, and potentially other contributions. When the blood contributions were suppressed with a contrast agent at 9.4 T, a small tissue-originated T1ρ change was consistently observed at the middle cortical layers of cat visual cortex during visual stimulation, which had different dynamic characteristics compared to hemodynamic fMRI such as a faster response and no post-stimulus undershoot. Functional tissue T1ρ is highly dependent on the magnetic field strength and experimental parameters such as the power of the spin-locking pulse. With a 500Hz spin-locking pulse, the tissue T1ρ without the blood contribution increased during visual stimulation, but decreased during acidosis-inducing hypercapnia and global ischemia, indicating different signal origins. Phantom studies suggest that it may have contribution from concentration decrease in metabolites. Even though the sensitivity is much weaker than BOLD and its exact interpretation needs further investigation, our results show that non-hemodynamic functional signal can be consistently observed by spin-lock fMRI.
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Affiliation(s)
- Tao Jin
- Neuroimaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15203, USA.
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Musthafa HSN, Dragneva G, Lottonen L, Merentie M, Petrov L, Heikura T, Ylä-Herttuala E, Ylä-Herttuala S, Gröhn O, Liimatainen T. Longitudinal rotating frame relaxation time measurements in infarcted mouse myocardium in vivo. Magn Reson Med 2012; 69:1389-95. [DOI: 10.1002/mrm.24382] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2011] [Revised: 05/02/2012] [Accepted: 05/28/2012] [Indexed: 12/21/2022]
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18
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Zhu XH, Chen W. In vivo oxygen-17 NMR for imaging brain oxygen metabolism at high field. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2011; 59:319-35. [PMID: 22027341 PMCID: PMC3202696 DOI: 10.1016/j.pnmrs.2011.04.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2011] [Accepted: 04/14/2011] [Indexed: 05/14/2023]
Affiliation(s)
- Xiao-Hong Zhu
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, 2021 6th St. SE, Minneapolis, MN 55455, USA.
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Quantitative proton MRI and MRS of the rat brain with a 3T clinical MR scanner. J Neuroradiol 2011; 38:90-7. [DOI: 10.1016/j.neurad.2009.11.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 11/03/2009] [Accepted: 11/13/2009] [Indexed: 11/21/2022]
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20
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Witschey WRT, Pilla JJ, Ferrari G, Koomalsingh K, Haris M, Hinmon R, Zsido G, Gorman JH, Gorman RC, Reddy R. Rotating frame spin lattice relaxation in a swine model of chronic, left ventricular myocardial infarction. Magn Reson Med 2011; 64:1453-60. [PMID: 20677236 DOI: 10.1002/mrm.22543] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
T1ρ relaxation times were quantified in a swine model of chronic, left ventricular myocardial infarction. It was found that there were low frequency relaxation mechanisms that suppress endogenous contrast at low spin-lock amplitudes and in T2-weighted images. A moderate amplitude spin-locking pulse could overcome these relaxation mechanisms. Relaxation dispersion data were measured over a range of RF field amplitudes, and a model was formulated to include dipole-dipole relaxation modulated by molecular rotation and an apparent exchange mechanism. These techniques may find some use in the clinic for the observation of chronic, left ventricular cardiac remodeling.
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Affiliation(s)
- Walter R T Witschey
- Department of Radiology, Medical Physics, University Hospital Freiburg, Freiburg im Breisgau, Germany.
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21
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Jokivarsi KT, Hiltunen Y, Gröhn H, Tuunanen P, Gröhn OHJ, Kauppinen RA. Estimation of the onset time of cerebral ischemia using T1rho and T2 MRI in rats. Stroke 2010; 41:2335-40. [PMID: 20814006 DOI: 10.1161/strokeaha.110.587394] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Time of ischemia onset is the most critical factor for patient selection for available drug treatment strategies. The purpose of this study was to evaluate the abilities of the absolute longitudinal rotating frame (T(1ρ)) and transverse (T(2)) MR relaxation times to estimate the onset time of ischemia in rats. METHODS Permanent middle cerebral artery occlusion in rats was used to induce focal cerebral ischemia and animals were imaged with multiparametric MRI at several time points up to 7 hours postischemia. Ischemic parenchyma was defined as tissue with apparent diffusion coefficient of water <70% from that in the contralateral nonischemic brain. RESULTS The difference in the absolute T(1ρ) and T(2) between ischemic and contralateral nonischemic striatum increased linearly within the first 6 hours of middle cerebral artery occlusion. The slopes for T(1ρ) and T(2) fits for both tissue types were similar; however, the time offsets were significantly longer for both MR parameters in the cortex than in the striatum. CONCLUSIONS T(1ρ) and T(2) MRI provide estimates for the onset time of cerebral ischemia requiring regional calibration curves from ischemic brain. Assuming that patients with suspected ischemic stroke are scanned by MRI within this timeframe, these MRI techniques may constitute unbiased tools for stroke onset time evaluation potentially aiding the decision-making for drug treatment strategies.
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Mangia S, Liimatainen T, Garwood M, Michaeli S. Rotating frame relaxation during adiabatic pulses vs. conventional spin lock: simulations and experimental results at 4 T. Magn Reson Imaging 2009; 27:1074-87. [PMID: 19559559 DOI: 10.1016/j.mri.2009.05.023] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2008] [Revised: 05/15/2009] [Accepted: 05/19/2009] [Indexed: 01/10/2023]
Abstract
Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse rotating frame relaxation rate constants (R(1rho) and R(2rho)). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this work, we investigate the dependencies of R(1rho) and R(2rho) due to dipolar interactions and anisochronous exchange (i.e., exchange between spins with different chemical shift deltaomega not equal0) on the properties of conventional spin-lock and adiabatic pulses, with particular emphasis on the latter ones which were not fully described previously. The results of simulations based on relaxation theory provide a foundation for formulating practical considerations for in vivo applications of rotating frame relaxation methods. Rotating frame relaxation measurements obtained from phantoms and from the human brain at 4 T are presented to confirm the theoretical predictions.
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Affiliation(s)
- Silvia Mangia
- Department of Radiology, Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, 55455, USA.
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23
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Quantitative magnetic resonance and optical imaging biomarkers of melanoma metastatic potential. Proc Natl Acad Sci U S A 2009; 106:6608-13. [PMID: 19366661 DOI: 10.1073/pnas.0901807106] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Noninvasive or minimally invasive prediction of tumor metastatic potential would facilitate individualized cancer management. Studies were performed on a panel of human melanoma xenografts that spanned the full range of metastatic potential measured by an in vivo lung colony assay and an in vitro membrane invasion culture system. Three imaging methods potentially transferable to the clinic [dynamic contrast-enhanced (DCE) MRI, T(1(rho))-MRI, and low-temperature fluorescence imaging (measurable on biopsy specimens)] distinguished between relatively less metastatic and more metastatic human melanoma xenografts in nude mice. DCE-MRI, analyzed with the shutter-speed relaxometric algorithm and using an arterial input function simultaneously measured in the left ventricle of the mouse heart, yielded a blood transfer rate constant, K(trans), that measures vascular perfusion/permeability. K(trans) was significantly higher in the core of the least metastatic melanoma (A375P) than in the core of the most metastatic melanoma (C8161). C8161 melanoma had more blood vascular structures but fewer functional blood vessels than A375P melanoma. The A375P melanoma exhibited mean T(1(rho)) values that were significantly higher than those of C8161 melanoma. Measurements of T(1) and T(2) relaxation times did not differ significantly between these 2 melanomas. The mitochondrial redox ratio, Fp/(Fp + NADH), where Fp and NADH are the fluorescences of oxidized flavoproteins and reduced pyridine nucleotides, respectively, varied linearly with the in vitro invasive potential of the 5 melanoma cell lines (A375P, A375M, A375P10, A375P5, and C8161). This study shows that a harsh microenvironment may promote melanoma metastasis and provides potential biomarkers of metastatic potential.
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Immonen RJ, Kharatishvili I, Sierra A, Einula C, Pitkänen A, Gröhn OH. Manganese enhanced MRI detects mossy fiber sprouting rather than neurodegeneration, gliosis or seizure-activity in the epileptic rat hippocampus. Neuroimage 2008; 40:1718-30. [DOI: 10.1016/j.neuroimage.2008.01.042] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2007] [Revised: 01/15/2008] [Accepted: 01/22/2008] [Indexed: 10/22/2022] Open
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Sibson NR, Lowe JP, Blamire AM, Martin MJ, Obrenovitch TP, Anthony DC. Acute astrocyte activation in brain detected by MRI: new insights into T(1) hypointensity. J Cereb Blood Flow Metab 2008; 28:621-32. [PMID: 17851455 DOI: 10.1038/sj.jcbfm.9600549] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Increases in the T(1) of brain tissue, which give rise to dark or hypointense areas on T(1)-weighted images using magnetic resonance imaging (MRI), are common to a number of neuropathologies including multiple sclerosis (MS) and ischaemia. However, the biologic significance of T(1) increases remains unclear. Using a multiparametric MRI approach and well-defined experimental models, we have experimentally induced increases in tissue T(1) to determine the underlying cellular basis of such changes. We have shown that a rapid acute increase in T(1) relaxation in the brain occurs in experimental models of both low-flow ischaemia induced by intrastriatal injection of endothelin-1 (ET-1), and excitotoxicity induced by intrastriatal injection of N-methyl-D-aspartate (NMDA). However, there appears to be no consistent correlation between increases in T(1) relaxation and changes in other MRI parameters (apparent diffusion coefficient, T(2) relaxation, or magnetisation transfer ratio of tissue water). Immunohistochemically, one common morphologic feature shared by the ET-1 and NMDA models is acute astrocyte activation, which was detectable within 2 h of intracerebral ET-1 injection. Pretreatment with an inhibitor of astrocyte activation, arundic acid, significantly reduced the spatial extent of the T(1) signal change induced by intrastriatal ET-1 injection. These findings suggest that an increase in T(1) relaxation may identify the acute development of reactive astrocytes within a central nervous system lesion. Early changes in T(1) may, therefore, provide insight into acute and reversible injury processes in neurologic patients, such as those observed before contrast enhancement in MS.
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Affiliation(s)
- Nicola R Sibson
- Experimental Neuroimaging Group, Department of Physiology, Anatomy & Genetics, University of Oxford, Oxford, UK.
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26
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Kettunen MI, Sierra A, Närväinen MJ, Valonen PK, Ylä-Herttuala S, Kauppinen RA, Gröhn OHJ. Low Spin-Lock Field T1 Relaxation in the Rotating Frame as a Sensitive MR Imaging Marker for Gene Therapy Treatment Response in Rat Glioma1. Radiology 2007; 243:796-803. [PMID: 17517934 DOI: 10.1148/radiol.2433052077] [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: 11/11/2022]
Abstract
PURPOSE To prospectively assess the effectiveness of T1 relaxation in the rotating frame (T1 rho) dispersion and the low spin-lock radiofrequency field (B(1)) T1 rho magnetic resonance (MR) imaging relaxation time in noninvasive monitoring of gene therapy response in BT4C glioma in rats. MATERIALS AND METHODS All animal studies were approved by the ethical committee of the National Laboratory Animal Center. Rats with BT4C gliomas (n=9) were treated with herpes simplex virus thymidine kinase gene therapy and were compared with untreated rats (n=5). Absolute T1 rho at a B(1) range of 2.0 x 10(-6) to 1.4 x 10(-4) T, T1, T2, and apparent diffusion constant were measured at 4.7 T during treatment. Statistical significance was tested by using repeated-measures analysis of variance. RESULTS A significant (P<.05) lengthening of T1 rho was observed beginning on the 4th day of treatment, and T1 rho values increased to be approximately 80% higher than values observed before treatment. These changes preceded T1 and T2 changes and resembled those of water diffusion. The T1 rho was associated with a treatment-induced decrease in cell density; this was the only measured MR imaging property that provided significant (P<.05) Pearson correlation with cell density in the tumor border. T1 rho relaxation dispersion, however, did not offer additional benefits over those offered in one B(1) experiment in the early phase of treatment. CONCLUSION T1 rho with low B(1) is an excellent MR imaging marker of early gene therapy response in gliomas. The low B(1) approach is not limited by specific absorption rate restrictions; this finding suggests that spin-lock methods could be applicable in clinical settings. (
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Affiliation(s)
- Mikko I Kettunen
- Department of Biotechnology and Molecular Medicine, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland.
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27
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Zhu XH, Zhang N, Zhang Y, Zhang X, Ugurbil K, Chen W. In vivo 17O NMR approaches for brain study at high field. NMR IN BIOMEDICINE 2005; 18:83-103. [PMID: 15770611 DOI: 10.1002/nbm.930] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
17O is the only stable oxygen isotope that can be detected by NMR. The quadrupolar moment of 17O spin (I = 5/2) can interact with local electric field gradients, resulting in extremely short T1 and T2 relaxation times which are in the range of several milliseconds. One unique NMR property of 17O spin is the independence of 17O relaxation times on the magnetic field strength, and this makes it possible to achieve a large sensitivity gain for in vivo 17O NMR applications at high fields. In vivo 17O NMR has two major applications for studying brain function and cerebral bioenergetics. The first application is to measure the cerebral blood flow (CBF) through monitoring the washout of inert H2 17O tracer in the brain tissue following an intravascular bolus injection of the 17O-labeled water. The second application, perhaps the most important one, is to determine the cerebral metabolic rate of oxygen utilization (CMRO2) through monitoring the dynamic changes of metabolically generated H2 17O from inhaled 17O-labeled oxygen gas in the brain tissue. One great merit of in vivo 17O NMR for the determination of CMRO2 is that only the metabolic H2 17O is detectable. This merit dramatically simplifies both CMRO2 measurement and quantification compared to other established methods. There are two major NMR approaches for monitoring H2 17O in vivo, namely direct approach by using 17O NMR detection (referred as direct in vivo 17O NMR approach) and indirect approach by using 1H NMR detection for measuring the changes in T2- or T1rho-weighted proton NMR signals caused by the 17O-1H scalar coupling and proton chemical exchange (referred as indirect in vivo 17O NMR approach). Both approaches are suitable for CBF measurements. However, recent studies indicated that the direct in vivo 17O NMR approach at high/ultrahigh fields appears to offer significant advantages for quantifying and imaging CMRO2. New developments have further demonstrated the feasibility for establishing a completely noninvasive in vivo 17O NMR approach for imaging CMRO2 in a rat brain during a brief 17O2 inhalation. This approach should be promising for studying the central role of oxidative metabolism in brain function and neurological diseases. Finally, the similar approach could potentially be applied to image CMRO2 noninvasively in human brain.
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Affiliation(s)
- Xiao-Hong Zhu
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, 2021 6th St SE, Minneapolis, MN 55455, USA
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Kavec M, Gröhn OHJ, Gröhn HI, Garwood M, Kauppinen RA. Dynamic dephasing changes in developing ischemic cerebral infarction in rats studied by Carr-PurcellT2magnetic resonance imaging. Magn Reson Med 2005; 53:960-4. [PMID: 15799047 DOI: 10.1002/mrm.20409] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Carr-Purcell (CP) T(2) MRI with adiabatic pulses, acquired with varying interecho interval (tau(CP)), was used to study the time course of T(2) and relative dynamic-dephasing contrast in the rat brain. Exposure to 30 min of middle cerebral artery occlusion (MCAo) resulted in an irreversible increase in absolute CP-T(2) relaxation times. This was not associated with signal change in the relative dynamic-dephasing images, as computed by subtracting short tau(CP) CP-T(2) images from long tau(CP) images and normalizing for long tau(CP) images. A day after MCAo strong CP-T(2) hyperintensity and low apparent diffusion coefficient were evident in the striatum with a decline in relative dynamic-dephasing contrast. Low dynamic dephasing contrast prevailed in striatum until day 5 post-MCAo, returning to control levels with similar time course to normalizing T(2) and diffusion. The present results show a novel behavior of dynamic-dephasing contrast in poststroke brain tissue, providing data to assess the age of infarction in association to T(2) images.
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Affiliation(s)
- Martin Kavec
- Department of Biomedical NMR and National Bio-NMR Facility, A. I.Virtanen Institute, University of Kuopio, Kuopio, Finland
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Kavec M, Gröhn OHJ, Kettunen MI, Silvennoinen MJ, Garwood M, Kauppinen RA. Acute cerebral ischemia in rats studied by Carr-Purcell spin-echo magnetic resonance imaging: assessment of blood oxygenation level-dependent and tissue effects on the transverse relaxation. Magn Reson Med 2004; 51:1138-46. [PMID: 15170833 DOI: 10.1002/mrm.20089] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Acute cerebral ischemia has been shown to be associated with an enhanced transverse relaxation rate in rat brain parenchyma, chiefly due to the blood oxygenation level-dependent (BOLD) effect. In this study, Carr-Purcell R(2) (CP R(2)), acquired both with short and long time intervals between centers of adiabatic pi-pulses (tau(CP)), was used to assess the contributions of BOLD and tissue effects to the transverse relaxation in two brain ischemia models of rat at 4.7 T. R(1rho) and diffusion MR images were also acquired in the same animals. During the first minutes of global ischemia, the long tau(CP) R(2) in brain parenchyma increased, whereas the short tau(CP) R(2) was unchanged. Based on the simulations, and using constraints of intravascular BOLD effect on parenchymal R(2), the former observation was ascribed to be due to susceptibility changes arising in the extravascular compartment. R(1rho) declined almost immediately after the onset of focal cerebral ischemia, and further declined during the evolution of ischemic damage. Interestingly, short tau(CP) CP R(2) started to decline after some 20 min of focal ischemia and declined over a time course similar to that of R(1rho), indicating that it may be an MRI marker for irreversible tissue changes in cerebral ischemia. The present results show that CP R(2) MRI can reveal both tissue- and blood-derived contrast changes in acute cerebral ischemia.
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Affiliation(s)
- Martin Kavec
- Department of Biomedical NMR and National Bio-NMR Facility, A.I. Virtanen Institute, University of Kuopio, Kuopio, Finland
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Kettunen MI, Gröhn OHJ, Kauppinen RA. Quantitative T1rho NMR spectroscopy of rat cerebral metabolites in vivo: effects of global ischemia. Magn Reson Med 2004; 51:875-80. [PMID: 15122667 DOI: 10.1002/mrm.20099] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The NMR relaxation times (T(1rho), T(2), and T(1)) of water, N-acetylaspartate (NAA), creatine (Cr), choline-containing compounds (Cho), and lactate (Lac) were quantified in rat brain at 4.7 T. In control animals, the cerebral T(1rho) figures, as determined with a spin-lock field of 1.0 G, were 575 +/- 30 ms, 380 +/- 19 ms, 705 +/- 53 ms, and 90 +/- 1 ms for NAA, Cr, Cho, and water, respectively. The T(1rho) figures were 62-103% longer than their respective T(2) values determined by a multiecho method. In global (ischemic) ischemia, T(1rho) of NAA declined by 34%, that of Cr and Cho did not change, and that of water increased by 10%. The T(1rho) of lactate in ischemic brain was 367 +/- 44 ms. Similar patterns of changes were observed in the multiecho T(2) of these cerebral metabolites. The T(1) of water and NAA changed in a fashion similar to that of T(1rho) and T(2). These results show differential responses in metabolite and water T(1rho) relaxation times following ischemia, and indicate that metabolite T(1rho) and T(2) relaxation times behave similarly in the ischemic brain. The contributions of dipolar and nondipolar effects on T(1rho) relaxation in vivo are discussed in this work.
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Affiliation(s)
- Mikko I Kettunen
- Department of Biomedical NMR and National Bio-NMR Facility, A.I.Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
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Borthakur A, Wheaton AJ, Gougoutas AJ, Akella SVS, Regatte RR, Charagundla SR, Reddy R. In vivo measurement of T1rho dispersion in the human brain at 1.5 tesla. J Magn Reson Imaging 2004; 19:403-9. [PMID: 15065163 DOI: 10.1002/jmri.20016] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To measure T1rho relaxation times and T1rho dispersion in the human brain in vivo. MATERIALS AND METHODS Magnetic resonance imaging (MRI) was performed on a 1.5-T GE Signa clinical scanner using the standard GE head coil. A fast spin-echo (FSE)-based T1rho-weighted MR pulse sequence was employed to obtain images from five healthy male volunteers. Optimal imaging parameters were determined while considering both the objective of the study and the guarantee that radio-frequency (RF) power deposition during MR did not exceed Food and Drug Administration (FDA)-mandated safety levels. RESULTS T1rho-weighted MR images showed excellent contrast between different brain tissues. These images were less blurred than corresponding T2-weighted images obtained with similar contrast, especially in regions between brain parenchyma and cerebrospinal fluid (CSF). Average T1rho values for white matter (WM), gray matter (GM), and CSF were 85 +/- 3, 99 +/- 1, and 637 +/- 78 msec, respectively, at a spin-locking field of 500 Hz. T1rho is 30% higher in the parenchyma and 78% higher in CSF compared to the corresponding T2 values. T1rho dispersion was observed between spin-locking frequencies 0 and 500 Hz. CONCLUSION T1rho-weighted MRI provides images of the brain with superb contrast and detail. T1rho values measured in the different brain tissues will serve as useful baseline values for analysis of T1rho changes associated with pathology.
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Affiliation(s)
- Arijitt Borthakur
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6100, USA.
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Mäkelä HI, De Vita E, Gröhn OHJ, Kettunen MI, Kavec M, Lythgoe M, Garwood M, Ordidge R, Kauppinen RA. B0 dependence of the on-resonance longitudinal relaxation time in the rotating frame (T1rho) in protein phantoms and rat brain in vivo. Magn Reson Med 2004; 51:4-8. [PMID: 14705038 DOI: 10.1002/mrm.10669] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
On-resonance longitudinal relaxation time in the rotating frame (T1rho) has been shown to provide unique information during the early minutes of acute stroke. In the present study, the contributions of the different relaxation mechanisms to on-resonance T1rho relaxation were assessed by determining relaxation rates (R1rho) in both protein phantoms and in rat brain at 2.35, 4.7, and 9.4 T. Similar to transverse relaxation rate (R2), R1rho increased substantially with increasing magnetic field strength (B0). The B0 dependence was more pronounced at weak spin-lock fields. In contrast to R1rho, longitudinal relaxation rate (R1) decreased as a function of increasing B0 field. The present data argue that dipole-dipole interaction forms only one pathway for T1rho relaxation and the contributions from other physicochemical factors need to be considered.
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Affiliation(s)
- Heidi I Mäkelä
- Department of Biomedical NMR and National Bio-NMR Facility, AI Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
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33
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Wheaton AJ, Borthakur A, Corbo M, Charagundla SR, Reddy R. Method for reduced SART1?-weighted MRI. Magn Reson Med 2004; 51:1096-102. [PMID: 15170827 DOI: 10.1002/mrm.20141] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
A reduced specific absorption rate (SAR) version of the T(1rho)-weighted MR pulse sequence was designed and implemented. The reduced SAR method employs a partial k-space acquisition approach in which a full power spin-lock pulse is applied to only the central phase-encode lines of k-space, while the remainder of k-space receives a low-power spin-lock pulse. Acquisition of high- and low-power phase-encode lines are interspersed chronologically to minimize average power deposition. In this way, the majority of signal energy in the central portion of k-space receives full T(1rho)-weighting, while the average SAR of the overall acquisition can be reduced, thereby lowering the minimum safely allowable TR. The pulse sequence was used to create T(1rho) maps of a phantom, an in vivo mouse brain, and the brain of a human volunteer. In the images of the human brain, SAR was reduced by 40% while the measurements of T(1rho) differed by only 2%. The reduced SAR sequence enables T(1rho)-weighted MRI in a clinical setting, even at high field strengths.
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Affiliation(s)
- Andrew J Wheaton
- Department of Radiology, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6100, USA.
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Abstract
The biochemical and physiological processes involved in apoptosis were described from the perspective of detection by standard, clinical, noninvasive imaging modalities. The difficulties of monitoring apoptosis in vivo were discussed. Magnetic resonance imaging (MRI) approaches used to study apoptosis were surveyed. The cell shrinkage associated with apoptosis can be detected due to changes in tissue water T(2) and T(1)rho relaxation times and apparent diffusion coefficient (ADC). Magnetic resonance spectroscopy (MRS) approaches used to study apoptosis in vivo have largely centered on the formation of cytoplasmic lipid bodies, detected by 1H MRS, and metabolic/bioenergetic changes detected by 31P and 13C MRS. The most successful approach to in vivo mapping of apoptosis uses the high specific binding of annexin V or synaptotagmin I to phosphatidylserine (PS) that appears on the extracellular plasma membrane of cells during apoptosis. Technetium-99m (99mTc)-radiolabeling of the annexin V and superparamagnetic iron oxide (SPIO) labeling of the C2 domain of synaptotagmin I allow good in vivo apoptosis detection by gamma camera imaging and MRI, respectively.
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Affiliation(s)
- Manfred Brauer
- Department of Chemistry and Biochemistry, University of Guelph, N1G 2W1, Guelph, Ontario, Canada.
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Gröhn OHJ, Mäkelä HI, Lukkarinen JA, DelaBarre L, Lin J, Garwood M, Kauppinen RA. On- and off-resonance T(1rho) MRI in acute cerebral ischemia of the rat. Magn Reson Med 2003; 49:172-6. [PMID: 12509834 DOI: 10.1002/mrm.10356] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The ability of on-resonance T(1rho) (T(1rho)) and off-resonance T(1rho) (T(1rho)(off)) measurements to indicate acute cerebral ischemia in a rat model of transient middle cerebral artery (MCA) occlusion was investigated at 4.7 T. T(1rho) was determined with B(1) fields of 0.4, 0.8, and 1.6 G, and T(1rho)(off) with five offset frequencies ((Delta)omega) ranging from 0-7.5 kHz at B(1) of 0.4 G, yielding effective B(1) (B(eff)) from 0.4 to 1.8 G. Diffusion, T(1), and T(2) were also quantified. Both T(1rho) and T(1rho)(off) acquired with (Delta)(o)< 2.5 kHz showed positive contrast during the first hours of MCA occlusion in the ischemic tissue delineated by low diffusion. Interestingly, T(1rho)(off) contrast acquired with (Delta)omega > 2.5 kHz was clearly less sensitive to ischemic alterations, and developed with a delayed time course. This discrepancy is thought to be a consequence of the frequency dependency of cross-relaxation during irradiation with spin-lock pulses.
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Affiliation(s)
- Olli H J Gröhn
- Department of Biomedical NMR, National Bio-NMR Facility, A.I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
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Gillies RJ, Raghunand N, Karczmar GS, Bhujwalla ZM. MRI of the tumor microenvironment. J Magn Reson Imaging 2002; 16:430-50. [PMID: 12353258 DOI: 10.1002/jmri.10181] [Citation(s) in RCA: 418] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The microenvironment within tumors is significantly different from that in normal tissues. A major difference is seen in the chaotic vasculature of tumors, which results in unbalanced blood supply and significant perfusion heterogeneities. As a consequence, many regions within tumors are transiently or chronically hypoxic. This exacerbates tumor cells' natural tendency to overproduce acids, resulting in very acidic pH values. The hypoxia and acidity of tumors have important consequences for antitumor therapy and can contribute to the progression of tumors to a more aggressive metastatic phenotype. Over the past decade, techniques have emerged that allow the interrogation of the tumor microenvironment with high resolution and molecularly specific probes. Techniques are available to interrogate perfusion, vascular distribution, pH, and pO(2) nondestructively in living tissues with relatively high precision. Studies employing these methods have provided new insights into the causes and consequences of the hostile tumor microenvironment. Furthermore, it is quite exciting that there are emerging techniques that generate tumor image contrast via ill-defined mechanisms. Elucidation of these mechanisms will yield further insights into the tumor microenvironment. This review attempts to identify techniques and their application to tumor biology, with an emphasis on nuclear magnetic resonance (NMR) approaches. Examples are also discussed using electron MR, optical, and radionuclear imaging techniques.
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Affiliation(s)
- Robert J Gillies
- Department of Biochemistry, Arizona Cancer Center, University of Arizona HSC, Tucson, Arizona 85724-5024, USA.
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Johanna Silvennoinen M, Kettunen MI, Clingman CS, Kauppinen RA. Blood NMR relaxation in the rotating frame: mechanistic implications. Arch Biochem Biophys 2002; 405:78-86. [PMID: 12176060 DOI: 10.1016/s0003-9861(02)00286-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The rotating frame nuclear magnetic resonance relaxation rate R(1rho) in the blood and cell lysate was studied at 4.7T to provide reference values for in vivo modeling and to address the mechanisms contributing to net relaxation. A strong dependence on oxygenation, hematocrit, and spin lock field strength B(1) (0.2-1.6G) was observed in whole blood, whereas in lysate the effects were severely attenuated. The results were further compared to transverse relaxation rate R(2). A good agreement in low-field asymptotes of these two relaxation rates was found. R(1rho) field dispersion was fitted to Lorenzian line shape and resulted in correlation times around 40 micros. The dispersion behavior was related to motional properties of intracellular hemoglobin and effects of susceptibility shift interface across the cell membrane induced by compartmentalization of Hb into cells in blood.
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Affiliation(s)
- M Johanna Silvennoinen
- Department of Biomedical NMR and National Bio NMR Facility, A.I. Virtanen Institute, University of Kuopio, Kuopio, Finland
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Kettunen MI, Gröhn OHJ, Silvennoinen MJ, Penttonen M, Kauppinen RA. Effects of intracellular pH, blood, and tissue oxygen tension on T1rho relaxation in rat brain. Magn Reson Med 2002; 48:470-7. [PMID: 12210911 DOI: 10.1002/mrm.10233] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The effects of intracellular pH (pH(i)), paramagnetic macroscopic, and microscopic susceptibility on T(1) in the rotating frame (T(1rho)) were studied in rat brain. Intracellular acidosis was induced by hypercapnia and pH(i), T(1rho), T(2), diffusion, and cerebral blood volume (CBV) were quantified. Taking into account the CBV contribution, a prolongation of parenchymal T(1rho) by 4.5% was ascribed to a change in tissue water relaxation caused by a one unit drop in pH(i). Blood T(1rho) was found to prolong linearly with blood oxygenation saturation (Y). The macroscopic susceptibility contribution to parenchymal T(1rho) was assessed both through BOLD and an iron oxide contrast agent, AMI-227. The T(1rho) data from these experiments could be described by intravascular effects with insignificant effects of susceptibility gradients on tissue water. Tissue oxygen tension (PtO(2)) was manipulated and monitored with microelectrodes to assess its plausible contribution to microscopic susceptibility and relaxation. Parenchymal T(1rho) was virtually unaffected by variations in the PtO(2), but T(1) was shortened in hyperoxia and T(2) showed a negative BOLD effect in hypoxia. It is demonstrated that pH(i) directly modulates tissue T(1rho), possibly through its effect on proton exchange; however, neither BOLD nor PtO(2) directly influence tissue T(1rho). The observations are discussed in the light of physicochemical mechanisms contributing to the ischemic T(1rho) changes.
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Affiliation(s)
- Mikko I Kettunen
- Department of Biomedical NMR and National Bio-NMR Facility, A.I.Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
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Mäkelä HI, Kettunen MI, Gröhn OHJ, Kauppinen RA. Quantitative T(1rho) and magnetization transfer magnetic resonance imaging of acute cerebral ischemia in the rat. J Cereb Blood Flow Metab 2002; 22:547-58. [PMID: 11973427 DOI: 10.1097/00004647-200205000-00006] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
It has been previously shown that T1 in the rotating frame (T(1rho)) is a very sensitive and early marker of cerebral ischemia and that, interestingly, it can provide prognostic information about the degree of subsequent neuronal damage. In the present study the authors have quantified T(1rho) together with the rate and other variables of magnetization transfer (MT) associated with spin interactions between the bulk and semisolid macromolecular pools by means of Z spectroscopy, to examine the possible overlap of mechanisms affecting these magnetic resonance imaging contrasts. Substantial prolongation of cerebral T(1rho) was observed minutes after induction of ischemia, this change progressing in a time-dependent manner. Difference Z spectra (contralateral nonischemic minus ischemic brain tissue) showed a significant positive reminder in the time points from 0.5 to 3 hours after induction of ischemia, the polarity of this change reversing by 24 hours. Detailed analysis of the MT variables showed that the initial Z spectral changes were due to concerted increase in the maximal MT (+3%) and amount of MT (+4%). Interestingly, the MT rates derived either from the entire frequency range of Z spectra or the time constant for the first-order forward exchange (k(sat)) were unchanged at this time, these variables reducing only one day after induction of ischemia. The authors conclude that T(1rho) changes in the acute phase of ischemia coincide with both elevated maximal MT and amount of MT. These changes occur independent of the overall MT rate and in the absence of net water gain to the tissue, whereas in the consolidating infarction the decrease in the rate and amount of MT, as well as the extensive prolongation of T(1rho), are associated with water accumulation.
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Affiliation(s)
- Heidi I Mäkelä
- National Bio-NMR Facility, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, FIN-70211 Kuopio, Finland
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Hakumäki JM, Gröhn OHJ, Tyynelä K, Valonen P, Ylä-Herttuala S, Kauppinen RA. Early gene therapy-induced apoptotic response in BT4C gliomas by magnetic resonance relaxation contrast T1 in the rotating frame. Cancer Gene Ther 2002; 9:338-45. [PMID: 11960284 DOI: 10.1038/sj.cgt.7700450] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2001] [Indexed: 11/09/2022]
Abstract
The design and evaluation of therapeutic gene transfection protocols and vectors are under extensive development. Magnetic resonance imaging (MRI) techniques can aid considerably in the development of experimental treatment approaches, as well as in determining treatment response by observing gross tissue morphology. However, through a unique set of contrast parameters, namely T1, T2, and diffusion, more information about tissue status can be obtained while delineating and classifying tumor characteristics in more detail. We show here that T1 relaxation in the rotating frame, T1rho, provides unique in vivo MRI contrast. Ganciclovir treatment of HSV-tk+BT4C gliomas, which effectively eradicates these tumors, resulted in significantly prolonged T1rho relaxation times in MRI already after 3 days of treatment, whereas conventional contrast parameters were elevated after 6-8 days of therapy. Interestingly, the prolonged T1rho values were observed while an increase in tumor volume was still taking place. The regions of elevated T1rho relaxation coincided with high apoptotic activity as determined by histology, suggesting that T1rho MRI contrast could be used as a novel early indicator of cytotoxic cell damage in gliomas.
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Affiliation(s)
- Juhana M Hakumäki
- National Bio-NMR Facility, AI Virtanen Institute for Molecular Sciences, University Hospital of Kuopio, FIN-70211 Kuopio, Finland
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Kettunen MI, Gröhn OHJ, Silvennoinen MJ, Penttonen M, Kauppinen RA. Quantitative assessment of the balance between oxygen delivery and consumption in the rat brain after transient ischemia with T2 -BOLD magnetic resonance imaging. J Cereb Blood Flow Metab 2002; 22:262-70. [PMID: 11891431 DOI: 10.1097/00004647-200203000-00003] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The balance between oxygen consumption and delivery in the rat brain after exposure to transient ischemia was quantitatively studied with single-spin echo T2-BOLD (blood oxygenation level-dependent) magnetic resonance imaging at 4.7 T. The rats were exposed to graded common carotid artery occlusions using a modification of the four-vessel model of Pulsinelli. T2, diffusion, and cerebral blood volume were quantified with magnetic resonance imaging, and CBF was measured with the hydrogen clearance method. A transient common carotid artery occlusion below the CBF value of approximately 20 mL x 100 g(-1) x min(-1) was needed to yield a T2 increase of 4.6 +/- 1.2 milliseconds (approximately 9% of cerebral T2) and 6.8 +/- 1.7 milliseconds (approximately 13% of cerebral T2) after 7 and 15 minutes of ischemia, respectively. Increases in CBF of 103 +/- 75% and in cerebral blood volume of 29 +/- 20% were detected in the reperfusion phase. These hemodynamic changes alone could account for only approximately one third of the T2 increase in luxury perfusion, suggesting that a substantial increase in blood oxygen saturation (resulting from reduced oxygen extraction by the brain) is needed to explain the magnetic resonance imaging observation.
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Affiliation(s)
- Mikko I Kettunen
- National Bio-NMR Facility and Cognitive Neurobiology Laboratory, A. I. Virtanen Institute for Molecular Sciences, University of Kuopio, Kuopio, Finland
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42
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Current awareness. NMR IN BIOMEDICINE 2002; 15:75-86. [PMID: 11840556 DOI: 10.1002/nbm.746] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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43
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Mäkelä HI, Gröhn OH, Kettunen MI, Kauppinen RA. Proton exchange as a relaxation mechanism for T1 in the rotating frame in native and immobilized protein solutions. Biochem Biophys Res Commun 2001; 289:813-8. [PMID: 11735118 DOI: 10.1006/bbrc.2001.6058] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
T1 relaxation in the rotating frame (T1rho) is a sensitive magnetic resonance imaging (MRI) contrast for acute brain insults. Biophysical mechanisms affecting T1rho relaxation rate (R1rho) and R1rho dispersion (dependency of R1rho on the spin-lock field) were studied in protein solutions by varying their chemical environment and pH in native, heat-denatured, and glutaraldehyde (GA) cross-linked samples. Low pH strongly reduced R1rho in heat-denatured phantoms displaying proton resonances from a number of side-chain chemical groups in high-resolution 1H NMR spectra. At pH of 5.5, R1rho dispersion was completely absent. In contrast, in the GA-treated phantoms with very few NMR visible side chain groups, acidic pH showed virtually no effect on R1rho. The present data point to a crucial role of proton exchange on R1rho and R1rho dispersion in immobilized protein solution mimicking tissue relaxation properties.
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Affiliation(s)
- H I Mäkelä
- National Bio-NMR Facility, University of Kuopio, Kuopio, FIN-70211, Finland
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