1
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Leigh R, Knutsson L, Zhou J, van Zijl PC. Imaging the physiological evolution of the ischemic penumbra in acute ischemic stroke. J Cereb Blood Flow Metab 2018; 38:1500-1516. [PMID: 28345479 PMCID: PMC6125975 DOI: 10.1177/0271678x17700913] [Citation(s) in RCA: 98] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
We review the hemodynamic, metabolic and cellular parameters affected during early ischemia and their changes as a function of approximate cerebral blood flow ( CBF) thresholds. These parameters underlie the current practical definition of an ischemic penumbra, namely metabolically affected but still viable brain tissue. Such tissue is at risk of infarction under continuing conditions of reduced CBF, but can be rescued through timely intervention. This definition will be useful in clinical diagnosis only if imaging techniques exist that can rapidly, and with sufficient accuracy, visualize the existence of a mismatch between such a metabolically affected area and regions that have suffered cell depolarization. Unfortunately, clinical data show that defining the outer boundary of the penumbra based solely on perfusion-related thresholds may not be sufficiently accurate. Also, thresholds for CBF and cerebral blood volume ( CBV) differ for white and gray matter and evolve with time for both inner and outer penumbral boundaries. As such, practical penumbral imaging would involve parameters in which the physiology is immediately displayed in a manner independent of baseline CBF or CBF threshold, namely pH, oxygen extraction fraction ( OEF), diffusion constant and mean transit time ( MTT). Suitable imaging technologies will need to meet this requirement in a 10-20 min exam.
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Affiliation(s)
- Richard Leigh
- 1 National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, USA
| | - Linda Knutsson
- 2 Department of Medical Radiation Physics, Lund University, Lund, Sweden.,3 Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Jinyuan Zhou
- 3 Department of Radiology, Johns Hopkins University, Baltimore, MD, USA.,4 F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
| | - Peter Cm van Zijl
- 3 Department of Radiology, Johns Hopkins University, Baltimore, MD, USA.,4 F.M. Kirby Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, MD, USA
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2
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Effects of hyperoxia on 18F-fluoro-misonidazole brain uptake and tissue oxygen tension following middle cerebral artery occlusion in rodents: Pilot studies. PLoS One 2017; 12:e0187087. [PMID: 29091934 PMCID: PMC5665507 DOI: 10.1371/journal.pone.0187087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 10/15/2017] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Mapping brain hypoxia is a major goal for stroke diagnosis, pathophysiology and treatment monitoring. 18F-fluoro-misonidazole (FMISO) positron emission tomography (PET) is the gold standard hypoxia imaging method. Normobaric hyperoxia (NBO) is a promising therapy in acute stroke. In this pilot study, we tested the straightforward hypothesis that NBO would markedly reduce FMISO uptake in ischemic brain in Wistar and spontaneously hypertensive rats (SHRs), two rat strains with distinct vulnerability to brain ischemia, mimicking clinical heterogeneity. METHODS Thirteen adult male rats were randomized to distal middle cerebral artery occlusion under either 30% O2 or 100% O2. FMISO was administered intravenously and PET data acquired dynamically for 3hrs, after which magnetic resonance imaging (MRI) and tetrazolium chloride (TTC) staining were carried out to map the ischemic lesion. Both FMISO tissue uptake at 2-3hrs and FMISO kinetic rate constants, determined based on previously published kinetic modelling, were obtained for the hypoxic area. In a separate group (n = 9), tissue oxygen partial pressure (PtO2) was measured in the ischemic tissue during both control and NBO conditions. RESULTS As expected, the FMISO PET, MRI and TTC lesion volumes were much larger in SHRs than Wistar rats in both the control and NBO conditions. NBO did not appear to substantially reduce FMISO lesion size, nor affect the FMISO kinetic rate constants in either strain. Likewise, MRI and TTC lesion volumes were unaffected. The parallel study showed the expected increases in ischemic cortex PtO2 under NBO, although these were small in some SHRs with very low baseline PtO2. CONCLUSIONS Despite small samples, the apparent lack of marked effects of NBO on FMISO uptake suggests that in permanent ischemia the cellular mechanisms underlying FMISO trapping in hypoxic cells may be disjointed from PtO2. Better understanding of FMISO trapping processes will be important for future applications of FMISO imaging.
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3
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Jensen-Kondering U, Manavaki R, Ejaz S, Sawiak SJ, Carpenter TA, Fryer TD, Aigbirhio FI, Williamson DJ, Baron JC. Brain hypoxia mapping in acute stroke: Back-to-back T2' MR versus 18F-fluoromisonidazole PET in rodents. Int J Stroke 2017; 12:752-760. [PMID: 28523963 DOI: 10.1177/1747493017706221] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Background Mapping the hypoxic brain in acute ischemic stroke has considerable potential for both diagnosis and treatment monitoring. PET using 18F-fluoro-misonidazole (FMISO) is the reference method; however, it lacks clinical accessibility and involves radiation exposure. MR-based T2' mapping may identify tissue hypoxia and holds clinical potential. However, its validation against FMISO imaging is lacking. Here we implemented back-to-back FMISO-PET and T2' MR in rodents subjected to acute middle cerebral artery occlusion. For direct clinical relevance, regions of interest delineating reduced T2' signal areas were manually drawn. Methods Wistar rats were subjected to filament middle cerebral artery occlusion, immediately followed by intravenous FMISO injection. Multi-echo T2 and T2* sequences were acquired twice during FMISO brain uptake, interleaved with diffusion-weighted imaging. Perfusion-weighted MR was also acquired whenever feasible. Immediately following MR, PET data reflecting the history of FMISO brain uptake during MR acquisition were acquired. T2' maps were generated voxel-wise from T2 and T2*. Two raters independently drew T2' lesion regions of interest. FMISO uptake and perfusion data were obtained within T2' consensus regions of interest, and their overlap with the automatically generated FMISO lesion and apparent diffusion coefficient lesion regions of interest was computed. Results As predicted, consensus T2' lesion regions of interest exhibited high FMISO uptake as well as substantial overlap with the FMISO lesion and significant hypoperfusion, but only small overlap with the apparent diffusion coefficient lesion. Overlap of the T2' lesion regions of interest between the two raters was ∼50%. Conclusions This study provides formal validation of T2' to map non-core hypoxic tissue in acute stroke. T2' lesion delineation reproducibility was suboptimal, reflecting unclear lesion borders.
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Affiliation(s)
- Ulf Jensen-Kondering
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.,2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.,3 Department of Radiology and Neuroradiology, University Medical Center Schleswig-Holstein, Kiel, Germany
| | - Roido Manavaki
- 4 Department of Radiology, University of Cambridge, Cambridge, UK
| | - Sohail Ejaz
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Stephen J Sawiak
- 2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - T Adrian Carpenter
- 2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Tim D Fryer
- 2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Franklin I Aigbirhio
- 2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - David J Williamson
- 2 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK
| | - Jean-Claude Baron
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, Cambridge, UK.,5 INSERM U894, Université Paris Descartes, Hôpital Sainte-Anne, Paris, France
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4
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Laurens E, Yeoh SD, Rigopoulos A, O'Keefe GJ, Tochon-Danguy HJ, Chong LW, White JM, Scott AM, Ackermann U. Fluorine-18 radiolabeling of a nitrophenyl sulfoxide and its evaluation in an SK-RC-52 model of tumor hypoxia. J Labelled Comp Radiopharm 2016; 59:416-23. [PMID: 27435268 DOI: 10.1002/jlcr.3426] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 06/09/2016] [Accepted: 06/10/2016] [Indexed: 11/10/2022]
Abstract
The significance of imaging hypoxia with the positron emission tomography ligand [(18) F]FMISO has been demonstrated in a variety of cancers. However, the slow kinetics of [(18) F]FMISO require a 2-h delay between tracer administration and patient scanning. Labeled chloroethyl sulfoxides have shown faster kinetics and higher contrast than [(18) F]FMISO in a rat model of ischemic stroke. However, these nitrogen mustard analogues are unsuitable for routine production and use in humans. Here, we report on the synthesis and in vitro and in vivo evaluation of a novel sulfoxide, which contains an ester moiety for hydrolysis and subsequent trapping in hypoxic cells. Non-decay corrected yields of radioactivity were 1.18 ± 0.24% (n = 27, 2.5 ± 0.5% decay corrected radiochemical yield) based on K[(18) F]F. The radiotracer did not show any defluorination and did not undergo metabolism in an in vitro assay using S9 liver fractions. Imaging studies using an SK-RC-52 tumor model in BALB/c nude mice have revealed that [(18) F]1 is retained in hypoxic tumors and has similar hypoxia selectivity to [(18) F]FMISO. Because of a three times faster clearance rate than [(18) F]FMISO from normoxic tissue, [(18) F]1 has emerged as a promising new radiotracer for hypoxia imaging.
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Affiliation(s)
- Evelyn Laurens
- School of Chemistry, The University of Melbourne, Melbourne, Australia.,Bio21 Institute, The University of Melbourne, Melbourne, Australia
| | - Shinn Dee Yeoh
- Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia
| | | | - Graeme J O'Keefe
- Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia
| | - Henri J Tochon-Danguy
- Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia.,Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Australia
| | - Lee Wenn Chong
- School of Chemistry, The University of Melbourne, Melbourne, Australia.,Bio21 Institute, The University of Melbourne, Melbourne, Australia
| | - Jonathan M White
- School of Chemistry, The University of Melbourne, Melbourne, Australia.,Bio21 Institute, The University of Melbourne, Melbourne, Australia
| | - Andrew M Scott
- Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia.,Olivia Newton-John Cancer Research Institute, Melbourne, Australia.,Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Australia.,School of Cancer Medicine, La Trobe University, Melbourne, Australia
| | - Uwe Ackermann
- Bio21 Institute, The University of Melbourne, Melbourne, Australia.,Department of Molecular Imaging and Therapy, Austin Health, Melbourne, Australia.,Olivia Newton-John Cancer Research Institute, Melbourne, Australia.,Faculty of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne, Australia
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5
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Lee GH, Kim JS, Oh SJ, Kang DW, Kim JS, Kwon SU. (18)F-fluoromisonidazole (FMISO) Positron Emission Tomography (PET) Predicts Early Infarct Growth in Patients with Acute Ischemic Stroke. J Neuroimaging 2014; 25:652-5. [PMID: 25311732 DOI: 10.1111/jon.12180] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Revised: 02/27/2014] [Accepted: 03/02/2014] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND AND PURPOSE (18) F-fluoromisonidazole (FMISO) positron emission tomography (PET) is used to image metabolically compromised but viable hypoxic tissue. We hypothesized that FMISO PET might predict early infarct growth in acute ischemic stroke patients with perfusion-diffusion mismatch in magnetic resonance imaging (MRI). METHODS We prospectively enrolled acute ischemic stroke patients who visited the emergency room within 48 hours after stroke onset and had perfusion-diffusion mismatch (>20%), as shown MRI. Infarct growth was defined as >20% increase of initial infarct volume or >5 mL in follow-up diffusion-weighted image 5 ± 2 days after stroke. The association between FMISO uptake and infarct growth was explored. RESULTS Of 19 enrolled patients, 10 (52.6%) showed increased FMISO uptake, with 8 of the latter showing infarct growth. None of the 9 patients who did not show FMISO uptake had infarct growth. FMISO uptake was significantly associated with infarct growth (Fisher's exact test; P < .01). FMISO PET scan had a sensitivity of 100% and a specificity of 82% (AUC = .909) in predicting infarct growth. CONCLUSIONS FMISO PET scan can predict early infarct growth in acute ischemic stroke patients with perfusion-diffusion mismatch in MRI.
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Affiliation(s)
- Gha-Hyun Lee
- Department of Neurology, Pusan National University Hospital, Pusan National University School of Medicine and Medical Research Institute, Busan, South Korea
| | - Jae Seung Kim
- Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Seung Jun Oh
- Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Dong-Wha Kang
- Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Jong S Kim
- Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
| | - Sun U Kwon
- Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, South Korea
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6
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Laurens E, Yeoh SD, Rigopoulos A, Cao D, Cartwright GA, O'Keefe GJ, Tochon-Danguy HJ, White JM, Scott AM, Ackermann U. Radiolabelling and evaluation of a novel sulfoxide as a PET imaging agent for tumor hypoxia. Nucl Med Biol 2014; 41:419-25. [PMID: 24767600 DOI: 10.1016/j.nucmedbio.2014.03.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 02/26/2014] [Accepted: 03/01/2014] [Indexed: 12/20/2022]
Abstract
[¹⁸F]FMISO is the most widely validated PET radiotracer for imaging hypoxic tissue. However, as a result of the pharmacokinetics of [¹⁸F]FMISO a 2h wait between tracer administration and patient scanning is required for optimal image acquisition. In order to develop hypoxia imaging agents with faster kinetics, we have synthesised and evaluated several F-18 labelled anilino sulfoxides. In this manuscript we report on the synthesis, in vitro and in vivo evaluation of a novel fluoroethyltriazolyl propargyl anilino sulfoxide. The radiolabelling of the novel tracer was achieved via 2-[¹⁸F]fluoroethyl azide click chemistry. Radiochemical yields were 23 ± 4% based on 2-[¹⁸F]fluoroethyl azide and 7 ± 2% based on K[¹⁸F]F. The radiotracer did not undergo metabolism or defluorination in an in vitro assay using S9 liver fractions. Imaging studies using SK-RC-52 tumors in BALB/c nude mice have indicated that the tracer may have a higher pO₂ threshold than [¹⁸F]FMISO for uptake in hypoxic tumors. Although clearance from muscle was faster than [¹⁸F]FMISO, uptake in hypoxic tumors was slower. The average tumor to muscle ratio at 2h post injection in large, hypoxic tumors with a volume greater than 686 mm³ was 1.7, which was similar to the observed ratio of 1.75 for [¹⁸F]FMISO. Although the new tracer showed improved pharmacokinetics when compared with the previously synthesised sulfoxides, further modifications to the chemical structure need to be made in order to offer significant in vivo imaging advantages over [¹⁸F]FMISO.
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Affiliation(s)
- Evelyn Laurens
- School of Chemistry and Bio21 Institute, The University of Melbourne, Parkville VIC 3052, Australia
| | - Shinn Dee Yeoh
- Centre for PET, Austin Health, Level 1 HSB, 145 Studley Road, Heidelberg VIC 3084, Australia
| | - Angela Rigopoulos
- Ludwig Institute for Cancer Research, Melbourne - Austin Branch, Heidelberg VIC 3084, Australia
| | - Diana Cao
- Ludwig Institute for Cancer Research, Melbourne - Austin Branch, Heidelberg VIC 3084, Australia
| | - Glenn A Cartwright
- Ludwig Institute for Cancer Research, Melbourne - Austin Branch, Heidelberg VIC 3084, Australia
| | - Graeme J O'Keefe
- Centre for PET, Austin Health, Level 1 HSB, 145 Studley Road, Heidelberg VIC 3084, Australia
| | - Henri J Tochon-Danguy
- Centre for PET, Austin Health, Level 1 HSB, 145 Studley Road, Heidelberg VIC 3084, Australia; School of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne VIC 3010, Australia
| | - Jonathan M White
- School of Chemistry and Bio21 Institute, The University of Melbourne, Parkville VIC 3052, Australia
| | - Andrew M Scott
- Centre for PET, Austin Health, Level 1 HSB, 145 Studley Road, Heidelberg VIC 3084, Australia; Ludwig Institute for Cancer Research, Melbourne - Austin Branch, Heidelberg VIC 3084, Australia; School of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne VIC 3010, Australia
| | - Uwe Ackermann
- Centre for PET, Austin Health, Level 1 HSB, 145 Studley Road, Heidelberg VIC 3084, Australia; Ludwig Institute for Cancer Research, Melbourne - Austin Branch, Heidelberg VIC 3084, Australia; School of Medicine, Dentistry and Health Sciences, The University of Melbourne, Melbourne VIC 3010, Australia.
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7
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Laurens E, Yeoh SD, Rigopoulos A, Cao D, Cartwright GA, O'Keefe GJ, Tochon-Danguy HJ, White JM, Scott AM, Ackermann U. Radiolabelling and evaluation of novel haloethylsulfoxides as PET imaging agents for tumor hypoxia. Nucl Med Biol 2012; 39:871-82. [DOI: 10.1016/j.nucmedbio.2012.01.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2011] [Revised: 11/04/2011] [Accepted: 01/10/2012] [Indexed: 10/14/2022]
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8
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Abstract
In ischemic stroke, positron-emission tomography (PET) established the imaging-based concept of penumbra. It defines hypoperfused, but functionally impaired, tissue with preserved viability that can be rescued by timely reperfusion. Diffusion-weighted and perfusion-weighted (PW) magnetic resonance imaging (MRI) translated the concept of penumbra to the concept of mismatch. However, the use of mismatch-based patient stratification for reperfusion therapy remains a matter of debate. The equivalence of mismatch and penumbra, as well as the validity of the classical mismatch concept is questioned for several reasons. First, methodological differences between PET and MRI lead to different definitions of the tissue at risk. Second, the mismatch concept is still poorly standardized among imaging facilities causing relevant variability in stroke research. Third, relevant conceptual issues (e.g., the choice of the adequate perfusion measure, the best quantitative approach to perfusion maps, and the required size of the mismatch) need further refinement. Fourth, the use of single thresholds does not account for the physiological heterogeneity of the penumbra and probabilistic approaches may be more promising. The implementation of this current knowledge into an optimized state-of-the-art mismatch model and its validation in clinical stroke studies remains a major challenge for future stroke research.
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Affiliation(s)
- Jan Sobesky
- Department of Neurology and Center for Stroke Research Berlin (CSB), Charité-Universitätsmedizin, Berlin, Germany.
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9
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Rojas S, Herance JR, Abad S, Jiménez X, Pareto D, Ruiz A, Torrent È, Figueiras FP, Popota F, Fernández-Soriano FJ, Planas AM, Gispert JD. Evaluation of Hypoxic Tissue Dynamics with 18F-FMISO PET in a Rat Model of Permanent Cerebral Ischemia. Mol Imaging Biol 2010; 13:558-564. [DOI: 10.1007/s11307-010-0371-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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10
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Molecular Imaging in Neurology and Psychiatry. Mol Imaging 2009. [DOI: 10.1007/978-3-540-76735-0_16] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
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11
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Abstract
Combining perfusion CT (CTP) with CT angiography (CTA) and noncontrast CT (NCCT) provides much more information about acute stroke pathophysiology than NCCT alone. This multimodal CT approach adds only a few minutes to the standard NCCT and is more accessible and rapidly available in most centres than MRI. CTP can distinguish between infarct core and penumbra, which is not possible with NCCT alone. A small infarct core and large penumbra, plus the presence of vessel occlusion on CTA may be an ideal imaging 'target' for thrombolysis. To date, multimodal CT has predominantly been assessed in hemispheric stroke due to its limited spatial coverage. This will become less of an issue as slice coverage continues to improve with new generation CT scanners. Apart from the concepts above, more specific CTP and CTA criteria that increase (or decrease) probability of response to thrombolytic treatment are yet to be determined. Nonetheless, CTP thus has the potential to improve patient selection for thrombolysis.
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Affiliation(s)
- Mark W Parsons
- Department of Neurology, John Hunter Hospital, and Hunter Medical Research Institute, University of Newcastle, Newcastle, NSW, Australia.
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12
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Takasawa M, Moustafa RR, Baron JC. Applications of nitroimidazole in vivo hypoxia imaging in ischemic stroke. Stroke 2008; 39:1629-37. [PMID: 18369176 DOI: 10.1161/strokeaha.107.485938] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND AND PURPOSE Nitroimidazole imaging is a promising contender for noninvasive in vivo mapping of brain hypoxia after stroke. However, there is a dearth of knowledge about the behavior of these compounds in the various pathophysiologic situations encountered in ischemic stroke. In this article we report the findings from a systematic review of the literature on the use of the nitroimidazoles to map hypoxia after stroke. SUMMARY OF REVIEW We describe the characteristics of nitroimidazoles as imaging tracers, their pharmacology, and results of both animal and clinical studies during and after focal cerebral ischemia. Findings in brain tumors are also presented to the extent that they enlighten results in stroke. Early results from application of kinetic modeling for quantitative measurement of tracer binding are briefly discussed. CONCLUSIONS Based on this literature review, nitroimidazole hypoxia imaging agents are of considerable interest in stroke because they appear, both in animal models and in humans, to specifically detect the severely hypoxic viable tissue, but not the reperfused nor the necrotic tissue. To fully realize this potential in stroke, however, formal validation by concurrent measurement of tissue oxygen tension, together with development of novel ligands with faster distribution kinetics, faster clearance from normal tissue, and well-defined trapping mechanisms, are important goals for future investigations.
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Affiliation(s)
- Masashi Takasawa
- University of Cambridge, Department of Clinical Neurosciences, Cambridge, UK
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13
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Abstract
The importance of hypoxia in disease pathogenesis and prognosis is gathering increasing clinical significance and having a greater impact on patient management and outcome. Previous efforts to evaluate hypoxia have included the invasive assessment of hypoxia with immunohistologic and histographic oxygen probes. The emergence of new radiotracers has allowed noninvasive assessment of hypoxia, with the most extensively investigated and validated positron emission tomography radiotracer of hypoxia to date being (18)F-fluoromisonodazole ((18)F-FMISO). This review discusses the relevance and biology of hypoxia in cells and organ systems, and reviews the laboratory and clinical applications of (18)F-FMISO in oncology and noncancer disease states.
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Affiliation(s)
- Sze Ting Lee
- Centre for PET, Austin Health, Heidelberg, Victoria, Australia
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14
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Souvatzoglou M, Grosu AL, Röper B, Krause BJ, Beck R, Reischl G, Picchio M, Machulla HJ, Wester HJ, Piert M. Tumour hypoxia imaging with [18F]FAZA PET in head and neck cancer patients: a pilot study. Eur J Nucl Med Mol Imaging 2007; 34:1566-75. [PMID: 17447061 DOI: 10.1007/s00259-007-0424-3] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2006] [Accepted: 02/22/2007] [Indexed: 12/12/2022]
Abstract
PURPOSE Hypoxia is an important negative prognostic factor for radiation treatment of head and neck cancer. This study was performed to evaluate the feasibility of use of (18)F-labelled fluoroazomycin arabinoside ([(18)F]FAZA) for clinical PET imaging of tumour hypoxia. METHODS Eleven patients (age 59.6 +/- 9 years) with untreated advanced head and neck cancer were included. After injection of approximately 300 MBq of [(18)F]FAZA, a dynamic sequence up to 60 min was acquired on an ECAT HR+ PET scanner. In addition, approximately 2 and 4 h p.i., static whole-body PET (n = 5) or PET/CT (n = 6) imaging was performed. PET data were reconstructed iteratively (OSEM) and fused with CT images (either an external CT or the CT of integrated PET/CT). Standardised uptake values (SUVs) and tumour-to-muscle (T/M) ratios were calculated in tumour and normal tissues. Also, the tumour volume displaying a T/M ratio >1.5 was determined. RESULTS Within the first 60 min of the dynamic sequence, the T/M ratio generally decreased, while generally increasing at later time points. At 2 h p.i., the tumour SUV(max) and SUV(mean) were found to be 2.3 +/- 0.5 (range 1.5-3.4) and 1.4 +/- 0.3 (range 1.0-2.1), respectively. The mean T/M ratio at 2 h p.i. was 2.0 +/- 0.3 (range 1.6-2.4). The tumour volume displaying a T/M ratio above 1.5 was highly variable. At 2 h p.i., [(18)F]FAZA organ distribution was determined as follows: kidney > gallbladder > liver > tumour > muscle > bone > brain > lung. CONCLUSION [(18)F]FAZA PET imaging appears feasible in head and neck cancer patients, and the achieved image quality is adequate for clinical purposes. Based on our initial results, [(18)F]FAZA warrants further evaluation as a hypoxia PET tracer for imaging of cancer.
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Affiliation(s)
- M Souvatzoglou
- Department of Nuclear Medicine, Technische Universität München, Ismaningerstr. 22, 81675 Munich, Germany
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15
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Falzon CL, Ackermann U, Spratt N, Tochon-Danguy HJ, White J, Howells D, Scott AM. F-18 labelledN,N-bis-haloethylamino-phenylsulfoxides — a new class of compounds for the imaging of hypoxic tissue. J Labelled Comp Radiopharm 2006. [DOI: 10.1002/jlcr.1129] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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16
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Dumarey NE, Massager N, Laureys S, Goldman S. Voxel-based assessment of spinal tap test-induced regional cerebral blood flow changes in normal pressure hydrocephalus. Nucl Med Commun 2005; 26:757-63. [PMID: 16096578 DOI: 10.1097/01.mnm.0000170937.90958.22] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
OBJECTIVE Normal pressure hydrocephalus (NPH) is a cause of dementia that may be amended by medical intervention. Its diagnosis is therefore of major importance and the establishment of response criteria to cerebrospinal fluid (CSF) shunting is essential. One of these criteria is the clinical response to spinal tap. The accuracy of the spinal tap test could potentially be improved by adding neuroimaging of regional cerebral blood flow (rCBF) changes to the response criteria. Statistical parametric mapping (SPM) is a voxel-based method of image analysis that may be used to statistically assess the significance of rCBF changes. The objective of this study was to evaluate, by SPM, spinal tap test-induced rCBF changes in patients with NPH syndrome. METHODS Forty patients with NPH syndrome underwent hexamethylpropylene amine oxime (HMPAO) brain single photon emission computed tomography (SPECT) before and after a spinal tap test (1-day split-dose protocol). The differences in rCBF between these pairs of scans were analysed by SPM in the whole group and between subgroups divided according to gait improvement at the spinal tap test. RESULTS In the whole group of patients, there was no statistical difference between pre- and post-spinal tap SPECT images. SPM analysis of patients grouped as a function of their clinical response to the spinal tap test revealed a significant post-spinal tap rCBF increase in the bilateral dorsolateral frontal and left mesiotemporal cortex in clinically responding compared with non-responding patients. CONCLUSION According to SPM analysis, gait improvement at the spinal tap test in patients with NPH syndrome is associated with an rCBF increase localized in the bilateral dorsolateral frontal and left mesiotemporal cortex.
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MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Brain/blood supply
- Brain/diagnostic imaging
- Cerebrospinal Fluid Pressure
- Cerebrovascular Circulation
- Female
- Gait Disorders, Neurologic/diagnosis
- Gait Disorders, Neurologic/etiology
- Gait Disorders, Neurologic/physiopathology
- Humans
- Hydrocephalus, Normal Pressure/complications
- Hydrocephalus, Normal Pressure/diagnostic imaging
- Hydrocephalus, Normal Pressure/physiopathology
- Image Interpretation, Computer-Assisted/methods
- Male
- Middle Aged
- Reproducibility of Results
- Sensitivity and Specificity
- Spinal Puncture/methods
- Tomography, Emission-Computed, Single-Photon/methods
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Affiliation(s)
- Nicolas E Dumarey
- Department of Nuclear Medicine and PET/Biomedical Cyclotron Unit, Hôpital Erasme, Université Libre de Bruxelles, 808 route de Lennik, B-1070 Brussels, Belgium.
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17
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Falcao ALE, Reutens DC, Markus R, Koga M, Read SJ, Tochon-Danguy H, Sachinidis J, Howells DW, Donnan GA. The resistance to ischemia of white and gray matter after stroke. Ann Neurol 2005; 56:695-701. [PMID: 15505775 DOI: 10.1002/ana.20265] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
A contributing factor to the failure of trials of neuroprotectants in acute ischemic stroke may be the differing vulnerability to ischemia of white compared with gray matter. To address this issue, we determined to establish the existence of potentially viable tissue in white matter and its evolution to infarction or salvage in both gray and white matter compartments in patients with ischemic stroke. Twenty-seven patients (mean age, 73.4 years) at a median of 16.5 hours after symptom onset were studied using the hypoxic marker 18F-misonidazole with positron emission tomography (PET). Tissue was segmented using an magnetic resonance probabilistic map. Although there was a greater volume of initially "at-risk tissue" in gray matter (58.3 cm3, 29.9-93.0 cm3 than white matter (42.0 cm3, 15.8-74.0 cm3; p <0.001) at the time of PET imaging, a higher proportion of this was still potentially viable in white matter (41.4%, 4.6-74.5%) than in gray matter (23.6%, 3.2-61.1%; p <0.05). However, a similar proportion in each compartment spontaneously survived. These data provide evidence for the existence of potentially salvageable tissue in human white matter and is consistent with it having a similar or even greater resistance to ischemia than gray matter. For the latter possibility, alternative therapeutic strategies may be required for its salvage.
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Affiliation(s)
- Antonio L E Falcao
- National Stroke Research Institute, Heidelberg Heights, Melbourne, Australia
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18
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Blankenberg FG. Molecular imaging with single photon emission computed tomography. How new tracers can be employed in the nuclear medicine clinic. ACTA ACUST UNITED AC 2005; 23:51-7. [PMID: 15508385 DOI: 10.1109/memb.2004.1337949] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Francis G Blankenberg
- Department of Radiology, Stanford University Hospital, Lucile Salter Packard Children's Hospital, Palo Alto, CA 94305, USA.
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19
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Markus R, Donnan G, Kazui S, Read S, Reutens D. Penumbral topography in human stroke: methodology and validation of the 'Penumbragram'. Neuroimage 2004; 21:1252-9. [PMID: 15050553 DOI: 10.1016/j.neuroimage.2003.11.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2003] [Revised: 11/05/2003] [Accepted: 11/21/2003] [Indexed: 11/17/2022] Open
Abstract
The location as well as the volume of the ischemic penumbra in human stroke is likely to influence the outcome of therapeutic intervention but its spatial extent is poorly characterized. Based on the observation that infarct expansion progresses from the center to the periphery of the penumbra in animal stroke models, we describe a method of mapping the three-dimensional spatial extent of the penumbra relative to the infarct in a 'Penumbragram'. Central, peripheral and external zones of the final infarct were defined according to median voxel distance from the infarct center (IC) and were further subdivided by coronal, sagittal and axial planes through the IC. In 10 patients with hypoxic, viable (penumbral) tissue identified by (18)F-Fluoromisonidazole positron emission tomography within 48 h of stroke onset, 'Penumbragrams' displaying the percentage of penumbra in each region were generated using anatomically co-registered data sets. The correlation between penumbral percentage and time from stroke onset was negative in the central (P < 0.05) and peripheral (P > 0.05) zones of the infarct and positive in external zones (P < 0.05). The validity of infarct segmentation was assessed by factor analysis with no a priori grouping of regions. Negative and positive correlations of penumbra volume and time from stroke onset were observed in seven (five corresponding to central zone of the infarct) and four (all in external zone) infarct regions and were measured reliably (Cronbach's alpha 0.84 and 0.9, respectively). The 'Penumbragram' is a valid method for objectively mapping the spatial extent of the penumbra, which is applicable to other imaging modalities.
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MESH Headings
- Aged
- Aged, 80 and over
- Algorithms
- Brain/diagnostic imaging
- Brain/physiopathology
- Brain Ischemia/diagnostic imaging
- Brain Ischemia/physiopathology
- Brain Mapping
- Factor Analysis, Statistical
- Female
- Fluorine Radioisotopes
- Humans
- Image Processing, Computer-Assisted
- Imaging, Three-Dimensional
- Infarction, Middle Cerebral Artery/diagnostic imaging
- Infarction, Middle Cerebral Artery/physiopathology
- Ischemic Attack, Transient/diagnostic imaging
- Ischemic Attack, Transient/physiopathology
- Male
- Misonidazole/analogs & derivatives
- Prognosis
- Reference Values
- Sensitivity and Specificity
- Statistics as Topic
- Tomography, Emission-Computed
- Tomography, X-Ray Computed
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Affiliation(s)
- Romesh Markus
- Department of Medicine, University of Melbourne, Melbourne, Australia
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20
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Blankenberg FG. Molecular imaging: The latest generation of contrast agents and tissue characterization techniques. J Cell Biochem 2004; 90:443-53. [PMID: 14523978 DOI: 10.1002/jcb.10635] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Molecular Imaging technologies will have a profound impact on both basic research and clinical imaging in the near future. As the field covers many different specialties and scientific disciplines it is not possible to review all in a single article. In the current article we will turn our attention to those modalities that are either currently in use or in development for the medical imaging clinic.
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Affiliation(s)
- Francis G Blankenberg
- Division of Pediatric Radiology/Department of Radiology, Stanford University Hospital, 300 Pasteur Drive Stanford, CA 94305, USA.
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21
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Abstract
PURPOSE OF REVIEW Imaging the penumbra is essential, not only to identify patients who might benefit from thrombolysis, but also to further understanding of the ischaemic process, thereby potentially revealing new opportunities for therapeutic intervention. Here we review recent imaging studies of the acute stroke process. RECENT FINDINGS Perfusion-computed tomography and computed tomography angiography enable assessment of the haemodynamic status and site of occlusion, leading to their promising use in guiding thrombolysis. The magnetic resonance concept of the diffusion-perfusion 'mismatch' being representative of penumbra appears to be an oversimplification. The mapping of simple variables such as time-to-peak might not directly reveal true penumbral perfusion levels. Also, lesions seen with diffusion-weighted imaging may be reversible as a result of early reperfusion. This reversal with subsequent normalization may represent selective neuronal damage. Late secondary injury, as indicated by the reappearance of the diffusion-weighted imaging lesion, has recently been documented; the mechanisms are unknown but form potential targets for future therapies. Despite these caveats, diffusion-weighted imaging-perfusion-weighted imaging remains the most useful approach to map the pathophysiology of stroke in the clinical setting. Acute/subacute flumazenil positron emission tomography studies are being used as markers of neuronal integrity to help shed further light on infarction thresholds, and potentially document selective neuronal loss. F-labelled fluoromisonidazole positron emission tomography imaging of brain hypoxia documents the temporal and spatial progression of the penumbra. SUMMARY The goal of understanding the complex process that is acute ischaemia in stroke, and subsequently the development of therapeutic strategies, continues to be advanced by imaging the penumbra in novel ways.
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Affiliation(s)
- Joseph V Guadagno
- Departments of Neurology and Radiology, University of Cambridge, Addenbrooke's Hospital, Cambridge, UK
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22
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Markus R, Reutens DC, Kazui S, Read S, Wright P, Chambers BR, Sachinidis JI, Tochon-Danguy HJ, Donnan GA. Topography and Temporal Evolution of Hypoxic Viable Tissue Identified by
18
F-Fluoromisonidazole Positron Emission Tomography in Humans After Ischemic Stroke. Stroke 2003; 34:2646-52. [PMID: 14563970 DOI: 10.1161/01.str.0000094422.74023.ff] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Background and Purpose—
We sought to characterize the spatial and temporal evolution of human cerebral infarction. Using a novel method of quantitatively mapping the distribution of hypoxic viable tissue identified by
18
F-fluoromisonidazole (
18
F-FMISO) PET relative to the final infarct, we determined its evolution and spatial topography in human stroke.
Methods—
Patients with acute middle cerebral artery territory stroke were imaged with
18
F-FMISO PET (n=19; <6 hours, 4; 6 to 16 hours, 4; 16 to 24 hours, 5; 24 to 48 hours, 6). The hypoxic volume (HV) comprised voxels with significant (
P
<0.05; >1 mL) uptake on statistical parametric mapping compared with 15 age-matched controls. Central, peripheral, and external zones of the corresponding infarct on the anatomically coregistered delayed CT were defined according to voxel distance from the infarct center and subdivided into 24 regions by coronal, sagittal, and axial planes. Maps (“penumbragrams”) displaying the percentage of HV in each region were generated for each time epoch.
Results—
Higher HV was observed in the central region of the infarct in patients studied within 6 hours of onset (analysis of covariance [ANCOVA];
P
<0.05) compared with those studied later, in whom the HV was mainly in the periphery or external to the infarct. HV was maximal in the superior, mesial, and posterior regions of the infarct (ANCOVA;
P
<0.05).
Conclusions—
These observations suggest that infarct expansion occurs at the expense of hypoxic tissue from the center to the periphery of the ischemic region in humans, similar to that seen in experimental animal models. These findings have important pathophysiological and therapeutic implications.
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Affiliation(s)
- R Markus
- Department of Medicine, University of Melbourne, Melbourne, Australia
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23
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Donnan GA, Davis SM. Neuroimaging, the ischaemic penumbra, and selection of patients for acute stroke therapy. Lancet Neurol 2002; 1:417-25. [PMID: 12849364 DOI: 10.1016/s1474-4422(02)00189-8] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Advances in neuroimaging have been central to the expansion of knowledge in the neurosciences over the past 20 years. One of the most important roles of brain imaging is in the selection of patients for acute stroke therapy. Currently, computed tomography (CT) is commonly used to select patients who have had strokes for thrombolytic therapy on the basis of the absence of haemorrhage and, more controversially, the presence of early CT changes of ischaemia. Since patients with ischaemic penumbra are more likely than those without to respond to therapy, identification of patients with this feature will become increasingly important. Although several imaging modalities can identify the penumbra, the most practical is magnetic resonance imaging (MRI) showing perfusion-weighted and diffusion-weighted imaging mismatch. Although uncertainties in image interpretation remain, surrogate MRI outcome measures are becoming an important component of translational research. Future developments in imaging technologies may provide other opportunities for surrogate outcome studies.
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Affiliation(s)
- Geoffrey A Donnan
- National Stroke Research Institute, Austin and Repatriation Medical Centre, University of Melbourne, West Heidelberg, Victoria, Australia.
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