Nederkoorn, Paul J. MD, PhD; van der Graaf, Yolanda MD, PhD;
MRA for Carotid Artery Stenosis.[Letter]
Stroke. 40(3):e77, March 2009.
Prabhakaran, Shyam MD, MS; Warrior, Lakshmi MD; Wells, Kalani R. RN; Jhaveri, Miral D. et al
The Utility of Quantitative Magnetic Resonance Angiography in the Assessment of Intracranial In-Stent Stenosis.[Letter]
Stroke. 40(3):991-993, March 2009.
Abstract
Background and Purpose-: Noninvasive screening for intracranial in-stent stenosis is often limited by artifact because of the stent or associated coils. We aimed to determine the utility of quantitative MRA (QMRA) as a screening tool for detecting intracranial in-stent stenosis.Methods-: We reviewed 14 patients who had intracranial stent placement with follow-up QMRA and conventional angiography at our institution. Socio-demographic, medical, clinical, and imaging data were abstracted from medical charts. A blinded interventional neurologist reviewed all angiograms for presence of >50% in-stent stenosis. We tested QMRA (mL/min) at varying thresholds as a predictor of angiographic results.Results-: Among 14 patients (mean age, 62 years; 12 female, 2 male), 13 patients had Neuroform stents placed for wide-neck cerebral aneurysms and 1 patient had a Wingspan stent placement for atherosclerotic stenosis. Lesions were located in the intracranial internal carotid artery in 57.2% (n=8), the middle cerebral artery in 14.3% (n=2), and vertebrobasilar arteries in 28.6% (n=4). On follow-up angiography, 2 patients (14.3%) had >50% in-stent stenosis on angiography. Time-of-flight MRA was nondiagnostic in each case because of artifact from the stent or coils. A >20% reduction in vessel-specific blood flow by QMRA was associated with presence of >50% in-stent stenosis on angiography (P=0.033). As a screening tool to predict >50% angiographic in-stent stenosis, the sensitivity, specificity, positive predictive value, and negative predictive value of QMRA were 100%, 92%, 67%, and 100%, respectively.Conclusion-: We found that QMRA is a promising screening tool to detect intracranial in-stent stenosis. Future prospective studies should focus on whether QMRA has a role in the detection of radiographic restenosis and prediction of clinical events
Perez, Estevo Santamarina MD, PhD; Delgado-Mederos, Raquel MD; Rubiera, Marta et al
Transcranial Duplex Sonography for Monitoring Hyperacute Intracerebral Hemorrhage.[Letter]
Stroke. 40(3):987-990, March 2009.
Abstract
Background and Purpose-: Early hematoma growth is one of the main determinants of mortality in patients with intracranial hemorrhage (ICH). Transcranial duplex sonography (TDS) might represent a useful tool for the bedside monitoring of early ICH enlargement. We aimed to correlate ICH volumes measured by TDS and CT scan in patients with ICH evaluated <3>20% in the hematoma volume at 6 hours.Results-: ICH was identified on TDS as an hyperechogenic mass located in the basal ganglia in 28 patients and in the lobar position in 6. Mean hematoma volume at baseline was 86+/-4 5 mL. At 6 hours, early hematoma growth was seen in 9 (26%) patients. An excellent correlation was found between TDS and CT measurements for all diameters: longitudinal (r=0.91, P<0.001), r="0.85," p="0.002)," r="0.79," p="0.022)" r="0.82," p="0.001).">
Balucani, Clotilde MD; Leys, Didier MD, PhD; Ringelstein, E Bernd MD, PhD; Kaste, Markku MD, PhD; Hacke, Werner MD, PhD; for the Executive Committee of the European Stroke Initiative;
Detection of Intracranial Atherosclerosis: Which Imaging Techniques Are Available in European Hospitals?
Stroke. 40(3):726-729, March 2009.
Abstract
Background and Purpose-: The diagnosis of intracranial atherosclerosis requires availability of appropriate imaging techniques. The objective was to evaluate the proportion of European hospitals where imaging techniques necessary to detect intracranial atherosclerosis are available.Method-: We randomly selected 886 hospitals in 25 countries and classified them in 3 categories according to the availability of 3 imaging techniques (transcranial color-coded duplex imaging, computed tomographic angiography, and magnetic resonance angiography): "all" when the 3 techniques were available, "at least 1," and "none." We compared the proportion of hospitals meeting these criteria, using the odds ratio method and Germany as reference.Results-: Two hundred seventy-two hospitals (30.7%) met criteria for all, 445 (50.2%) met criteria for at least 1, and 169 (19.1%) met criteria for none. In 2005, they had admitted, respectively, 139,118, 160, 393, and 62 667 stroke patients. Brain CT or MRI were available in 820 (92.6%) hospitals, computed tomographic angiography in 619 (69.9%), magnetic resonance angiography in 498 (56.2%), and transcranial color-coded duplex in 352 (39.7%). Compared to Germany, Greece (OR, 0.11; 95% CI, 0.01-0.88), Iberic countries (OR, 0.11; 95% CI, 0.05-0.27), Baltic countries (OR, 0.13; 95% CI, 0.03-0.56), Poland (OR, 0.40; 95% CI, 0.21-0.77), and France (OR, 0.52; 95% CI, 0.31-0.89), had significantly less hospitals in the all group.Conclusion-: In Europe, less than one-third of ischemic stroke patients are admitted in hospitals with all imaging techniques available to detect intracranial atherosclerosis. There are important differences between countries
Kwee, Robert M. MD; van Engelshoven, Jos M.A. MD; Mess, Werner H. et al
Reproducibility of Fibrous Cap Status Assessment of Carotid Artery Plaques by Contrast-Enhanced MRI.
Stroke.
Status
published online before print, 25 June 2009
Abstract
Background and Purpose-: Reproducibility in identifying the fibrous cap (FC) of carotid artery plaques by noncontrast-enhanced MRI has been shown to be poor. The objective of this study was to assess the reproducibility of multisequence MRI, including contrast-enhanced images, in assessing FC status.Methods-: Forty-five symptomatic patients with 30% to 69% carotid artery stenosis underwent a multisequence MRI protocol, which included contrast-enhanced images. FC status (ie, discrimination between fibrotic and/or calcified plaques, plaques with a lipid-rich necrotic core and an intact and thick FC, and plaques with a lipid-rich necrotic core and a thin and/or ruptured FC) was independently assessed by 3 observers of which one also scored all images on a different occasion. Linear weighted kappa coefficients ([kappa]) were calculated as indicators of inter- and intraobserver agreement.Results-: On a per-slice basis, interobserver agreement was good ([kappa]=0.60, 0.64, and 0.71), whereas intraobserver agreement was very good ([kappa]=0.86). On a per-plaque basis, interobserver agreement was good ([kappa]=0.64, 0.69, and 0.78), whereas intraobserver agreement was very good ([kappa]=0.96).Conclusion-: This study found good interobserver and very good intraobserver agreement in assessing FC status of carotid artery plaques. Future studies are warranted to determine the predictive value of FC status assessment by multisequence MRI, including contrast-enhanced images, on the occurrence of (recurrent) cerebral ischemic events
Detection of Intracranial Atherosclerosis: Which Imaging Techniques Are Available in European Hospitals?
Stroke. 40(3):726-729, March 2009.
Abstract
Background and Purpose-: The diagnosis of intracranial atherosclerosis requires availability of appropriate imaging techniques. The objective was to evaluate the proportion of European hospitals where imaging techniques necessary to detect intracranial atherosclerosis are available.Method-: We randomly selected 886 hospitals in 25 countries and classified them in 3 categories according to the availability of 3 imaging techniques (transcranial color-coded duplex imaging, computed tomographic angiography, and magnetic resonance angiography): "all" when the 3 techniques were available, "at least 1," and "none." We compared the proportion of hospitals meeting these criteria, using the odds ratio method and Germany as reference.Results-: Two hundred seventy-two hospitals (30.7%) met criteria for all, 445 (50.2%) met criteria for at least 1, and 169 (19.1%) met criteria for none. In 2005, they had admitted, respectively, 139,118, 160, 393, and 62 667 stroke patients. Brain CT or MRI were available in 820 (92.6%) hospitals, computed tomographic angiography in 619 (69.9%), magnetic resonance angiography in 498 (56.2%), and transcranial color-coded duplex in 352 (39.7%). Compared to Germany, Greece (OR, 0.11; 95% CI, 0.01-0.88), Iberic countries (OR, 0.11; 95% CI, 0.05-0.27), Baltic countries (OR, 0.13; 95% CI, 0.03-0.56), Poland (OR, 0.40; 95% CI, 0.21-0.77), and France (OR, 0.52; 95% CI, 0.31-0.89), had significantly less hospitals in the all group.Conclusion-: In Europe, less than one-third of ischemic stroke patients are admitted in hospitals with all imaging techniques available to detect intracranial atherosclerosis. There are important differences between countries
Kwee, Robert M. MD; van Engelshoven, Jos M.A. MD; Mess, Werner H. et al
Reproducibility of Fibrous Cap Status Assessment of Carotid Artery Plaques by Contrast-Enhanced MRI.
Stroke.
Status
published online before print, 25 June 2009
Abstract
Background and Purpose-: Reproducibility in identifying the fibrous cap (FC) of carotid artery plaques by noncontrast-enhanced MRI has been shown to be poor. The objective of this study was to assess the reproducibility of multisequence MRI, including contrast-enhanced images, in assessing FC status.Methods-: Forty-five symptomatic patients with 30% to 69% carotid artery stenosis underwent a multisequence MRI protocol, which included contrast-enhanced images. FC status (ie, discrimination between fibrotic and/or calcified plaques, plaques with a lipid-rich necrotic core and an intact and thick FC, and plaques with a lipid-rich necrotic core and a thin and/or ruptured FC) was independently assessed by 3 observers of which one also scored all images on a different occasion. Linear weighted kappa coefficients ([kappa]) were calculated as indicators of inter- and intraobserver agreement.Results-: On a per-slice basis, interobserver agreement was good ([kappa]=0.60, 0.64, and 0.71), whereas intraobserver agreement was very good ([kappa]=0.86). On a per-plaque basis, interobserver agreement was good ([kappa]=0.64, 0.69, and 0.78), whereas intraobserver agreement was very good ([kappa]=0.96).Conclusion-: This study found good interobserver and very good intraobserver agreement in assessing FC status of carotid artery plaques. Future studies are warranted to determine the predictive value of FC status assessment by multisequence MRI, including contrast-enhanced images, on the occurrence of (recurrent) cerebral ischemic events
Barrett, Kevin M. MD, MSc; Ding, Yong Hong MD; Wagner, Douglas P. PhD +; Kallmes, David F. MD, PhD; Johnston, Karen C. MD, MSc; for the ASAP Investigators;
Change in Diffusion-Weighted Imaging Infarct Volume Predicts Neurologic Outcome at 90 Days: Results of the Acute Stroke Accurate Prediction (ASAP) Trial Serial Imaging Substudy.
Stroke. 40(7):2422-2427, July 2009.
Abstract
Background and Purpose-: Predictive models of outcome after ischemic stroke have incorporated acute diffusion-weighted MRI (DWI) information with mixed results. We hypothesized that serial measurements of DWI infarct volume would be predictive of functional outcome after ischemic stroke.Methods-: The prospective Acute Stroke Accurate Prediction (ASAP) Study included a prespecified serial imaging subgroup who underwent DWI studies at baseline (<24>=95).Results-: In total, 169 cases from the ASAP study had serial DWI scans with a measurable lesion at baseline, follow-up, or both. The median baseline National Institutes of Health Stroke Scale score was 6 (interquartile range, 3 to 13). For each 10 cm3 of growth in DWI infarct volume, the OR for achieving an excellent outcome by modified Rankin Scale was 0.52 (95% CI, 0.38 to 0.71) and for the Barthel Index was 0.64 (95% CI, 0.51 to 0.79). Adjusting for clinically important covariates, the OR for an excellent modified Rankin Scale outcome was 0.57 (95% CI, 0.37 to 0.88) and excellent Barthel Index outcome was 0.75 (95% CI, 0.56 to 1.01).Conclusions-: Based on these data, the likelihood of achieving an excellent neurological outcome diminishes substantially with growth in DWI infarct volume in the first 5 days after ischemic stroke of mild to moderate severity.(C) 2009 American Heart Association, Inc.
Zaro-Weber, Olivier MD; Moeller-Hartmann, Walter MD et al
The Performance of MRI-Based Cerebral Blood Flow Measurements in Acute and Subacute Stroke Compared With 15O-Water Positron Emission Tomography: Identification of Penumbral Flow.
Stroke. 40(7):2413-2421, July 2009.
Abstract
Background and Purpose-: Perfusion-weighted MRI-based maps of cerebral blood flow (CBFMRI) are considered a good MRI measure of penumbral flow in acute ischemic stroke but are seldom used in clinical routine due to methodical issues. We validated CBFMRI on quantitative CBF measurement by 15O-water positron emission tomography (CBFPET).Material and Methods-: Comparative CBFMRI and CBFPET were performed in patients with acute and subacute stroke. In a voxel-based seed-growing technique, predefined CBFMRI thresholds (<40,>
The Performance of MRI-Based Cerebral Blood Flow Measurements in Acute and Subacute Stroke Compared With 15O-Water Positron Emission Tomography: Identification of Penumbral Flow.
Stroke. 40(7):2413-2421, July 2009.
Abstract
Background and Purpose-: Perfusion-weighted MRI-based maps of cerebral blood flow (CBFMRI) are considered a good MRI measure of penumbral flow in acute ischemic stroke but are seldom used in clinical routine due to methodical issues. We validated CBFMRI on quantitative CBF measurement by 15O-water positron emission tomography (CBFPET).Material and Methods-: Comparative CBFMRI and CBFPET were performed in patients with acute and subacute stroke. In a voxel-based seed-growing technique, predefined CBFMRI thresholds (<40,>
Silva, Gisele Sampaio MD, PhD; Vicari, Perla MD, PhD; Figueiredo, Maria Stella et al
Brain Magnetic Resonance Imaging Abnormalities in Adult Patients With Sickle Cell Disease: Correlation With Transcranial Doppler Findings.
Stroke. 40(7):2408-2412, July 2009.
Abstract
Background and Purpose-: Brain imaging abnormalities were reported in up to 44% of children with sickle cell disease (SCD). The prevalence of neuroimaging abnormalities in adult patients with SCD and their relationship to transcranial Doppler is still unclear. Our objectives were to study the frequency of MRI and MR angiography abnormalities in adults with SCD and to define what transcranial Doppler velocities are associated with intracranial stenoses detected by MR angiography.Methods-: We examined all adult patients (>16 years) with SCD followed in the hematology outpatient clinic at our university hospital with MRI, MR angiography, and transcranial Doppler.Results-: We evaluated 50 patients. The overall prevalence of MRI abnormalities was 60%. Abnormal MRI findings were more frequent when vessel tortuosity or stenoses were present on MR angiography (P<0.01). p="0.01).">
Stroke. 40(7):2408-2412, July 2009.
Abstract
Background and Purpose-: Brain imaging abnormalities were reported in up to 44% of children with sickle cell disease (SCD). The prevalence of neuroimaging abnormalities in adult patients with SCD and their relationship to transcranial Doppler is still unclear. Our objectives were to study the frequency of MRI and MR angiography abnormalities in adults with SCD and to define what transcranial Doppler velocities are associated with intracranial stenoses detected by MR angiography.Methods-: We examined all adult patients (>16 years) with SCD followed in the hematology outpatient clinic at our university hospital with MRI, MR angiography, and transcranial Doppler.Results-: We evaluated 50 patients. The overall prevalence of MRI abnormalities was 60%. Abnormal MRI findings were more frequent when vessel tortuosity or stenoses were present on MR angiography (P<0.01). p="0.01).">
Jonsdottir, Kristjana Yr PhD, MSc; Ostergaard, Leif DMSc, PhD, MD, MSc; Mouridsen, Kim et al
Predicting Tissue Outcome From Acute Stroke Magnetic Resonance Imaging: Improving Model Performance by Optimal Sampling of Training Data.
Stroke.
Status
published online before print, 16 July 2009
Abstract
Background and Purpose-: It has been hypothesized that algorithms predicting the final outcome in acute ischemic stroke may provide future tools for identifying salvageable tissue and hence guide individualized therapy. We developed means of quantifying predictive model performance to identify model training strategies that optimize performance and reduce bias in predicted lesion volumes.Methods-: We optimized predictive performance based on the area under the receiver operating curve for logistic regression and used simulated data to illustrate the effect of an unbalanced (unequal number of infarcting and surviving voxels) training set on predicted infarct risk. We then tested the performance and optimality of models based on perfusion-weighted, diffusion-weighted, and structural MRI modalities by changing the proportion of mismatch voxels in balanced training material.Results-: Predictive performance (area under the receiver operating curve) based on all brain voxels is excessively optimistic and lacks sensitivity in performance in mismatch tissue. The ratio of infarcting and noninfarcting voxels used for training predictive algorithms significantly biases tissue infarct risk estimates. Optimal training strategy is obtained using a balanced training set. We show that 60% of noninfarcted voxels consists of mismatch voxels in an optimal balanced training set for the patient data presented.Conclusions-: An equal number of infarcting and noninfarcting voxels should be used when training predictive models. The choice of test and training sets critically affects predictive model performance and should be closely evaluated before comparisons across patient cohorts
Predicting Tissue Outcome From Acute Stroke Magnetic Resonance Imaging: Improving Model Performance by Optimal Sampling of Training Data.
Stroke.
Status
published online before print, 16 July 2009
Abstract
Background and Purpose-: It has been hypothesized that algorithms predicting the final outcome in acute ischemic stroke may provide future tools for identifying salvageable tissue and hence guide individualized therapy. We developed means of quantifying predictive model performance to identify model training strategies that optimize performance and reduce bias in predicted lesion volumes.Methods-: We optimized predictive performance based on the area under the receiver operating curve for logistic regression and used simulated data to illustrate the effect of an unbalanced (unequal number of infarcting and surviving voxels) training set on predicted infarct risk. We then tested the performance and optimality of models based on perfusion-weighted, diffusion-weighted, and structural MRI modalities by changing the proportion of mismatch voxels in balanced training material.Results-: Predictive performance (area under the receiver operating curve) based on all brain voxels is excessively optimistic and lacks sensitivity in performance in mismatch tissue. The ratio of infarcting and noninfarcting voxels used for training predictive algorithms significantly biases tissue infarct risk estimates. Optimal training strategy is obtained using a balanced training set. We show that 60% of noninfarcted voxels consists of mismatch voxels in an optimal balanced training set for the patient data presented.Conclusions-: An equal number of infarcting and noninfarcting voxels should be used when training predictive models. The choice of test and training sets critically affects predictive model performance and should be closely evaluated before comparisons across patient cohorts
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