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Nael K, Tadayon E, Wheelwright D, Metry A, Fifi JT, Tuhrim S, De Leacy RA, Doshi AH, Chang HL, Mocco J. Defining Ischemic Core in Acute Ischemic Stroke Using CT Perfusion: A Multiparametric Bayesian-Based Model. AJNR Am J Neuroradiol 2019; 40:1491-1497. [PMID: 31413007 DOI: 10.3174/ajnr.a6170] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 07/07/2019] [Indexed: 12/17/2022]
Abstract
BACKGROUND AND PURPOSE The Bayesian probabilistic method has shown promising results to offset noise-related variability in perfusion analysis. Using CTP, we aimed to find optimal Bayesian-estimated thresholds based on multiparametric voxel-level models to estimate the ischemic core in patients with acute ischemic stroke. MATERIALS AND METHODS Patients with anterior circulation acute ischemic stroke who had baseline CTP and achieved successful recanalization were included. In a subset of patients, multiparametric voxel-based models were constructed between Bayesian-processed CTP maps and follow-up MRIs to identify pretreatment CTP parameters that were predictive of infarction using robust logistic regression. Subsequently CTP-estimated ischemic core volumes from our Bayesian model were compared against routine clinical practice oscillation singular value decomposition-relative cerebral blood flow <30%, and the volumetric accuracy was assessed against final infarct volume. RESULTS In the constructed multivariate voxel-based model, 4 variables were identified as independent predictors of infarction: TTP, relative CBF, differential arterial tissue delay, and differential mean transit time. At an optimal cutoff point of 0.109, this model identified infarcted voxels with nearly 80% accuracy. The limits of agreement between CTP-estimated ischemic core and final infarct volume ranged from -25 to 27 mL for the Bayesian model, compared with -61 to 52 mL for oscillation singular value decomposition-relative CBF. CONCLUSIONS We established thresholds for the Bayesian model to estimate the ischemic core. The described multiparametric Bayesian-based model improved consistency in CTP estimation of the ischemic core compared with the methodology used in current clinical routine.
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Affiliation(s)
- K Nael
- From the Department of Radiology (K.N., E.T., A.M., A.H.D.), Neuroimaging Advanced and Exploratory Lab
| | - E Tadayon
- From the Department of Radiology (K.N., E.T., A.M., A.H.D.), Neuroimaging Advanced and Exploratory Lab
| | | | - A Metry
- From the Department of Radiology (K.N., E.T., A.M., A.H.D.), Neuroimaging Advanced and Exploratory Lab
| | - J T Fifi
- Departments of Neurology (D.W., J.F., S.T.).,Neurosurgery (J.F., R.A.D.L., J.M.)
| | - S Tuhrim
- Departments of Neurology (D.W., J.F., S.T.)
| | | | - A H Doshi
- From the Department of Radiology (K.N., E.T., A.M., A.H.D.), Neuroimaging Advanced and Exploratory Lab
| | - H L Chang
- Population Health Science and Policy (H.C.), Icahn School of Medicine at Mount Sinai, New York, New York
| | - J Mocco
- Neurosurgery (J.F., R.A.D.L., J.M.)
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Copen WA, Yoo AJ, Rost NS, Morais LT, Schaefer PW, González RG, Wu O. In patients with suspected acute stroke, CT perfusion-based cerebral blood flow maps cannot substitute for DWI in measuring the ischemic core. PLoS One 2017; 12:e0188891. [PMID: 29190675 PMCID: PMC5708772 DOI: 10.1371/journal.pone.0188891] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2017] [Accepted: 09/25/2017] [Indexed: 12/02/2022] Open
Abstract
Background Neuroimaging may guide acute stroke treatment by measuring the volume of brain tissue in the irreversibly injured “ischemic core.” The most widely accepted core volume measurement technique is diffusion-weighted MRI (DWI). However, some claim that measuring regional cerebral blood flow (CBF) with CT perfusion imaging (CTP), and labeling tissue below some threshold as the core, provides equivalent estimates. We tested whether any threshold allows reliable substitution of CBF for DWI. Methods 58 patients with suspected stroke underwent DWI and CTP within six hours of symptom onset. A neuroradiologist outlined DWI lesions. In CBF maps, core pixels were defined by thresholds ranging from 0%-100% of normal, in 1% increments. Replicating prior studies, we used receiver operating characteristic (ROC) curves to select thresholds that optimized sensitivity and specificity in predicting DWI-positive pixels, first using only pixels on the side of the brain where infarction was clinically suspected (“unilateral” method), then including both sides (“bilateral”). We quantified each method and threshold’s accuracy in estimating DWI volumes, using sums of squared errors (SSE). For the 23 patients with follow-up studies, we assessed whether CBF-derived volumes inaccurately exceeded follow-up infarct volumes. Results The areas under the ROC curves were 0.89 (unilateral) and 0.90 (bilateral). Various metrics selected optimum CBF thresholds ranging from 29%-32%, with sensitivities of 0.79–0.81, and specificities of 0.83–0.85. However, for the unilateral and bilateral methods respectively, volume estimates derived from all CBF thresholds above 28% and 22% were less accurate than disregarding imaging and presuming every patient’s core volume to be zero. The unilateral method with a 30% threshold, which recent clinical trials have employed, produced a mean core overestimation of 65 mL (range: –82–191), and exceeded follow-up volumes for 83% of patients, by up to 191 mL. Conclusion CTP-derived CBF maps cannot substitute for DWI in measuring the ischemic core.
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Affiliation(s)
- William A. Copen
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
- * E-mail:
| | - Albert J. Yoo
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
- Division of Neurointervention, Texas Stroke Institute, Fort Worth, Texas, United States of America
| | - Natalia S. Rost
- Harvard Medical School, Boston, Massachusetts, United States of America
- Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Lívia T. Morais
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Pamela W. Schaefer
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
| | - R. Gilberto González
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
| | - Ona Wu
- Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
- Harvard Medical School, Boston, Massachusetts, United States of America
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Copen WA, Lev MH, Rapalino O. Brain perfusion: computed tomography and magnetic resonance techniques. HANDBOOK OF CLINICAL NEUROLOGY 2016; 135:117-135. [PMID: 27432662 DOI: 10.1016/b978-0-444-53485-9.00006-4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Cerebral perfusion imaging provides assessment of regional microvascular hemodynamics in the living brain, enabling in vivo measurement of a variety of different hemodynamic parameters. Perfusion imaging techniques that are used in the clinical setting usually rely upon X-ray computed tomography (CT) or magnetic resonance imaging (MRI). This chapter reviews CT- and MRI-based perfusion imaging techniques, with attention to image acquisition, clinically relevant aspects of image postprocessing, and fundamental differences between CT- and MRI-based techniques. Correlations with cerebrovascular physiology and potential clinical applications of perfusion imaging are reviewed, focusing upon the two major classes of neurologic disease in which perfusion imaging is most often performed: primary perfusion disorders (including ischemic stroke, transient ischemic attack, and reperfusion syndrome), and brain tumors.
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Affiliation(s)
- William A Copen
- Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA.
| | - Michael H Lev
- Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Otto Rapalino
- Division of Neuroradiology, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
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Abstract
OPINION STATEMENT Recent years have seen the development of novel neuroimaging techniques whose roles in the management of acute stroke are sometimes confusing and controversial. This may be attributable in part to a focus on establishing simplified algorithms and terminology that omit consideration of the basic pathophysiology of cerebral ischemia and, consequently, of the full potential for optimizing patients' care based upon their individual imaging findings. This review begins by discussing cerebral hemodynamic physiology and of the effects of hemodynamic disturbances upon the brain. Particular attention will be paid to the hemodynamic measurements and markers of tissue injury that are provided by common clinical imaging techniques, with the goal of enabling greater confidence and flexibility in understanding the potential uses of these techniques in various clinical roles, which will be discussed in the remainder of the review.
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Affiliation(s)
- William A Copen
- Massachusetts General Hospital, Division of Neuroradiology, GRB-273A, 55 Fruit Street, Boston, MA, 02114, USA,
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Abstract
Traditionally non-contrast CT has been considered the first choice imaging modality for acute stroke. Acute ischemic stroke patients presenting to the hospital within 3-hours from symptom onset and without any visible hemorrhages or large lesions on CT images are considered optimum reperfusion therapy candidates. However, non-contrast CT alone has been unable to identify best reperfusion therapy candidates outside this window. New advanced imaging techniques are now being used successfully for this purpose. Non-invasive CT or MR angiography images can be obtained during initial imaging evaluation for identification and characterization of vascular lesions, including occlusions, aneurysms, and malformations. Either CT-based perfusion imaging or MRI-based diffusion and perfusion imaging performed immediately upon arrival of a patient to the hospital helps estimate the extent of fixed core and penumbra in ischemic lesions. Patients having occlusive lesions with small fixed cores and large penumbra are preferred reperfusion therapy candidates.
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Copen WA, Schaefer PW, Wu O. MR perfusion imaging in acute ischemic stroke. Neuroimaging Clin N Am 2012; 21:259-83, x. [PMID: 21640299 DOI: 10.1016/j.nic.2011.02.007] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Magnetic resonance (MR) perfusion imaging offers the potential for measuring brain perfusion in acute stroke patients, at a time when treatment decisions based on these measurements may affect outcomes dramatically. Rapid advancements in both acute stroke therapy and perfusion imaging techniques have resulted in continuing redefinition of the role that perfusion imaging should play in patient management. This review discusses the basic pathophysiology of acute stroke, the utility of different kinds of perfusion images, and research on the continually evolving role of MR perfusion imaging in acute stroke care.
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Affiliation(s)
- William A Copen
- Department of Radiology, Division of Neuroradiology, Massachusetts General Hospital, GRB-273A, 55 Fruit Street, Boston, MA 02114, USA.
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Olivot JM, Mlynash M, Zaharchuk G, Straka M, Bammer R, Schwartz N, Lansberg MG, Moseley ME, Albers GW. Perfusion MRI (Tmax and MTT) correlation with xenon CT cerebral blood flow in stroke patients. Neurology 2009; 72:1140-5. [PMID: 19332690 DOI: 10.1212/01.wnl.0000345372.49233.e3] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND While stable xenon CT (Xe-CT) cerebral blood flow (CBF) is an accepted standard for quantitative assessment of cerebral hemodynamics, the accuracy of magnetic resonance perfusion-weighted imaging (PWI-MRI) is unclear. The Improved PWI Methodology in Acute Clinical Stroke Study compares PWI findings with Xe-CT CBF values in patients experiencing symptomatic severe cerebral hypoperfusion. METHODS We compared mean transit time (MTT) and Tmax PWI-MRI with the corresponding Xe-CT CBF values in 25 coregistered regions of interest (ROIs) of multiple sizes and locations in nine subacute stroke patients. Comparisons were performed with Pearson correlation coefficients (R). We performed receiver operating characteristic (ROC) curve analyses to define the threshold of Tmax and absolute MTT that could best predict a Xe-CT CBF <20 mL/100 g/minute. RESULTS The subjects' mean (SD) age was 50 (15) years, the median (interquartile range [IQR]) NIH Stroke Scale score was 2 (2-6), and the median (IQR) time between MRI and Xe-CT was 12 (-7-19) hours. The total number of ROIs was 225, and the median (IQR) ROI size was 550 (360-960) pixels. Tmax correlation with Xe-CT CBF (R = 0.63, p < 0.001) was stronger than absolute MTT (R = 0.55, p < 0.001), p = 0.049. ROC curve analysis found that Tmax >4 seconds had 68% sensitivity, 80% specificity, and 77% accuracy and MTT >10 seconds had 68% sensitivity, 77% specificity, and 75% accuracy for predicting ROIs with Xe-CT CBF <20 mL/100 g/minute. CONCLUSION Our results suggest that in subacute ischemic stroke patients, Tmax correlates better than absolute mean transit time (MTT) with xenon CT cerebral blood flow (Xe-CT CBF) and that both Tmax >4 seconds and MTT >10 seconds are strongly associated with Xe-CT CBF <20 mL/100 g/minute. CBF = cerebral blood flow; DBP = diastolic blood pressure; DEFUSE = Diffusion and Perfusion Imaging Evaluation for Understanding Stroke Evolution; DWI = diffusion-weighted imaging; EPITHET = Echoplanar Imaging Thrombolytic Evaluation Trial; FOV = field of view; ICA = internal carotid artery; IQR = interquartile range; MCA = middle cerebral artery; MTT = mean transit time; NIHSS = NIH Stroke Scale; PWI = perfusion-weighted imaging; PWI-MRI = magnetic resonance perfusion-weighted imaging; ROC = receiver operating characteristic; ROI = region of interest; SBP = systolic blood pressure; SVD = singular value decomposition; Xe-CT = xenon CT.
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Affiliation(s)
- J-M Olivot
- Department of Neurology and Neurological Sciences and the Stanford Stroke Center, Stanford University Medical Center, 701 Welch Rd., Suite 325, Palo Alto, CA 94304, USA.
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Machida K, Oohashi N, Nakano H. [Method of injection of contrast medium for brain perfusion CT]. Nihon Hoshasen Gijutsu Gakkai Zasshi 2002; 58:962-6. [PMID: 12515965 DOI: 10.6009/jjrt.kj00001364338] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Perfusion computed tomography (CT) has great value for detecting stroke and evaluating blood flow in the brain. With perfusion CT, it is possible to obtain two absolute values, cerebral blood flow (CBF) (ml/min/100g) and cerebral blood volume (CBV) (%). In using this examination, the main problem is the method of iodine injection. The maximum slope of time-attenuation curve in organs must be reached before the peak enhancement time of the sagittal sinus. To solve this problem, we used a new method in which total injection volume is 30ml, and the rate of injection is 9ml/sec. The data acquisition time is one second for each scan, and the time interval is one second, for 20 scans in total. With this method, we can obtain reliable information on blood flow in the damaged brain. The most common examination used for the detection of brain blood flow is single-phased dynamic CT with Xe inhalation. However, the Xe inhalant examination is difficult to use in the routine clinical setting. Perfusion CT will be more useful for the detection of brain blood flow.
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Affiliation(s)
- Keiichi Machida
- Department of Radiology, Toho University Oomori Hospital, Japan
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