9 results on '"Derksen, C."'
Search Results
2. Associations between spatially autocorrelated patterns of SSM/I-derived prairie snow cover and atmospheric circulation
- Author
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Derksen, C., primary, Wulder, M., additional, Ledrew, E., additional, and Goodison, B., additional
- Published
- 1998
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3. Validation of the transcranial Doppler rescue criteria for mechanical thrombectomy.
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Khan A, Saqqur M, Shuaib A, Khan K, Sharma VK, Brunser A, Eggers J, Mikulik R, Katsanos AH, Sergentanis TN, Vadikolias K, Rubiera M, Shahripour RB, Nguyen HT, Martínez-Sánchez P, Safouris A, Heliopoulos I, Salam A, Derksen C, Voumvourakis K, Psaltopoulou T, Alexandrov AW, Alexandrov AV, and Tsivgoulis G
- Subjects
- Humans, Female, Male, Middle Aged, Aged, Prospective Studies, Reproducibility of Results, Thrombectomy methods, Computed Tomography Angiography methods, Blood Flow Velocity, Stroke diagnostic imaging, Stroke therapy, Treatment Outcome, Ultrasonography, Doppler, Transcranial methods, Sensitivity and Specificity
- Abstract
Background and Purpose: Transcranial Doppler (TCD) identifies acute stroke patients with arterial occlusion where treatment may not effectively open the blocked vessel. This study aimed to examine the clinical utility and prognostic value of TCD flow findings in patients enrolled in a multicenter prospective study (CLOTBUST-PRO)., Methods: Patients enrolled with intracranial occlusion on computed tomography angiography (CTA) who underwent urgent TCD evaluation before intravenous thrombolysis was included in this analysis. TCD findings were assessed using the mean flow velocity (MFV) ratio, comparing the reciprocal ratios of the middle cerebral artery (MCA) depths bilaterally (affected MCA-to-contralateral MCA MFV [aMCA/cMCA MFV ratio])., Results: A total of 222 patients with intracranial occlusion on CTA were included in the study (mean age: 64 ± 14 years, 62% men). Eighty-eight patients had M1 MCA occlusions; baseline mean National Institutes of Health Stroke Scale (NIHSS) score was 16, and a 24-hour mean NIHSS score was 10 points. An aMCA/cMCA MFV ratio of <.6 had a sensitivity of 99%, specificity of 16%, positive predictive value (PV) of 60%, and negative PV of 94% for identifying large vessel occlusion (LVO) including M1 MCA, terminal internal carotid artery, or tandem ICA/MCA. Thrombolysis in Brain Ischemia scale, with (grade ≥1) compared to without flow (grade 0), showed a sensitivity of 17.1%, specificity of 86.9%, positive PV of 62%, and negative PV of 46% for identifying LVO., Conclusions: TCD is a valuable modality for evaluating arterial circulation in acute ischemic stroke patients, demonstrating significant potential as a screening tool for intravenous/intra-arterial lysis protocols., (© 2024 The Author(s). Journal of Neuroimaging published by Wiley Periodicals LLC on behalf of American Society of Neuroimaging.)
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- 2024
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4. Comparison of Carotid Doppler Ultrasound to Other Angiographic Modalities in the Measurement of Carotid Artery Stenosis.
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Boyko M, Kalashyan H, Becher H, Romanchuk H, Saqqur M, Rempel JL, Derksen C, Shuaib A, and Khan K
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- Aged, Carotid Stenosis pathology, Female, Humans, Male, Middle Aged, Stroke, Angiography, Digital Subtraction methods, Carotid Stenosis diagnostic imaging, Computed Tomography Angiography methods, Magnetic Resonance Angiography methods, Ultrasonography, Doppler methods
- Abstract
Background and Purpose: The purpose of this study was to compare Doppler ultrasound (DUS) to other angiographic modalities: computed tomography angiography (CTA), magnetic resonance angiography (MRA), and digital subtraction angiography (DSA)., Methods: All DUS studies performed at Stroke Prevention Clinic (SPC) from 2011 to 2013 and referred for further angiographic modalities were included. Patients were excluded if the corresponding angiographic modality was not performed within 6 months of DUS. Patients were also excluded if they underwent interventions before DUS or between the time of DUS and the corresponding angiographic modality. The degree of stenosis was classified as mild (<50%), moderate (50-69%), severe (70-99%), or occlusion (100%)., Results: In total, 245 patients were identified. Nine patients were excluded (3.7%). Overall 472 Doppler studies of single ICAs from 236 patients were included in our analysis. Age was 65 ± 13 years and 136 patients were males (57.6%). There was an excellent agreement between DUS and CTA (kappa = .9 [P < .001], n = 274), good agreement with MRA (kappa = .8 [P < .001], n = 242), and excellent agreement with DSA (kappa = .92 [P < .001], n = 18). There was excellent agreement between CTA and MRA (kappa = .87, n = 46)., Conclusion: Doppler ultrasound performed in a dedicated SPC by an experienced sonographer and reviewed by a certified stroke neurologist serves as a reliable initial screening tool in determining carotid artery stenosis., (© 2018 by the American Society of Neuroimaging.)
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- 2018
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5. Transcranial Doppler and Transcranial Color Duplex in Defining Collateral Cerebral Blood Flow.
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Saqqur M, Khan K, Derksen C, Alexandrov A, and Shuaib A
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- Hemodynamics, Humans, Subarachnoid Hemorrhage diagnostic imaging, Vasospasm, Intracranial diagnostic imaging, Brain Ischemia diagnostic imaging, Cerebrovascular Circulation physiology, Stroke diagnostic imaging, Ultrasonography, Doppler, Color methods, Ultrasonography, Doppler, Transcranial methods
- Abstract
In an acute stroke setting, transcranial Doppler (TCD) and transcranial color-coded duplex (TCCD) have an important diagnostic utility in the monitoring of an arterial occlusion and microemboli detection. In addition, TCD has proven to be a very useful tool in the detection and progression of cerebral vasospasm in patients with subarachnoid hemorrhage. TCD/TCCD may have an important role in defining collateral blood flow (CF) in stroke patients. It is a noninvasive technique and can be utilized repeatedly allowing for changes in the blood flow dynamics as treatment is delivered. In this review, we outlined the evolving role of TCD/TCCD in defining CF in patients with an acute ischemic stroke, predicting clinical outcome and monitoring the treatment's efficacy of the CF augmentation., (© 2018 by the American Society of Neuroimaging.)
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- 2018
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6. Cerebral blood flow dynamics of orthostatic transient ischemic attacks in a patient with carotid dissection and fibromuscular dysplasia.
- Author
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Gupta D, Derksen C, Saqqur M, Khan K, Jeerakathil T, and Shuaib A
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- Blood Flow Velocity, Carotid Artery, Internal, Dissection complications, Carotid Artery, Internal, Dissection diagnosis, Dizziness diagnosis, Dizziness etiology, Fibromuscular Dysplasia complications, Fibromuscular Dysplasia diagnostic imaging, Humans, Ischemic Attack, Transient diagnosis, Ischemic Attack, Transient etiology, Male, Middle Aged, Carotid Artery, Internal, Dissection physiopathology, Cerebrovascular Circulation, Dizziness physiopathology, Fibromuscular Dysplasia physiopathology, Ischemic Attack, Transient physiopathology, Ultrasonography, Doppler methods
- Abstract
In patients with critical carotid stenosis and ischemic stroke, it is crucial to determine whether distal hypoperfusion or artery-to-artery embolism is the predominant mechanism. The role of transcranial doppler (TCD) in this setting is vital. We report a patient with fibromuscular dysplasia and recurrent orthostatic transient ischemic attacks where fall in cerebral perfusion was clearly demonstrated by TCD., (Copyright © 2012 by the American Society of Neuroimaging.)
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- 2014
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7. Derivation of transcranial Doppler criteria for angiographically proven middle cerebral artery vasospasm after aneurysmal subarachnoid hemorrhage.
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Sebastian J, Derksen C, Khan K, Ibrahim M, Hameed B, Siddiqui M, Chow M, Findlay JM, Shuaib A, and Saqqur M
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- Adult, Alberta epidemiology, Causality, Cerebral Angiography statistics & numerical data, Comorbidity, Feasibility Studies, Female, Humans, Male, Middle Aged, Prognosis, Reproducibility of Results, Risk Factors, Sensitivity and Specificity, Infarction, Middle Cerebral Artery diagnosis, Infarction, Middle Cerebral Artery epidemiology, Subarachnoid Hemorrhage diagnosis, Subarachnoid Hemorrhage epidemiology, Ultrasonography, Doppler, Transcranial statistics & numerical data, Vasospasm, Intracranial diagnosis, Vasospasm, Intracranial epidemiology
- Abstract
Background: Transcranial Doppler (TCD) has been subjected to criticism for detecting vasospasm (VSP). Our study's aim is to derive criteria for middle cerebral artery (MCA) vasospasm (MCA-VSP) based on cerebral angiography (CA)., Methods: A prospective data of patients with aneurysmal subarachnoid hemorrhage (aSAH) from January 2004 to August 2009. TCD was performed daily from day 2 to 14 from symptom's onset. Follow-up CA was done at day 7-9. TCD mean flow velocities (MFV) of all vessels at baseline (b), middle (m) and before CA (preangio) were recorded. Several MCA MFV ratios were computed. Moderate to severe VSP on CA was defined as >1/3 luminal narrowing. Univariate and stepwise logistic regression analysis were performed., Results: One hundred sixty-nine patients (338 MCA) with aSAH were included, mean age: 54.8 ± 13, women: 103 (62%). Twenty-nine patients (8.6%) had angiographic MCA-VSP. TCD scoring system of 3 points for MCA-VSP was computed based on (a) bMCA MFV ≥ 120 cm/s (sensitivity: 59.3%, specificity: 85%, PPV: 36.4%, NPV: 93.5%, P < .001) (1 point), Preangio MCA MFV ≥ 150 cm/s (79.3%, 89.9%, 39%, 97.3%, <.001) (1 point), and affected preangio MCA/bMCA MFV ratio ≥ 1.5 (84%, 63%, 25.6%, 96.3%, .001) (1 point). The score of 3 has 96% sensitivity and 96% specificity (OR: 300) whereas the score of 1 has 12% sensitivity and 58% specificity (OR: 4.3) for identifying MCA-VSP., Conclusion: TCD stringent criteria for moderate to severe MCA-VSP are feasible and applicable in aSAH population., (Copyright © 2012 by the American Society of Neuroimaging.)
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- 2013
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8. Transcranial Doppler and cerebral augmentation in acute ischemic stroke.
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Saqqur M, Ibrahim M, Butcher K, Khan K, Emery D, Manawadu D, Derksen C, Schwindt B, and Shuaib A
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- Adult, Aged, Brain Ischemia complications, Female, Humans, Male, Middle Aged, Stroke etiology, Treatment Outcome, Ultrasonography, Interventional methods, Aorta diagnostic imaging, Balloon Occlusion methods, Brain Ischemia diagnostic imaging, Brain Ischemia therapy, Stroke diagnostic imaging, Stroke therapy, Ultrasonography, Doppler, Transcranial methods
- Abstract
Background: Collateral flow augmentation using partial aortic occlusion may improve cerebral perfusion in acute stroke. We assessed the effect of partial aortic occlusion on arterial flow velocities of acute stroke patients., Methods: Patients with neurological deficits following thrombolysis were treated with partial aortic occlusion. Transcranial Doppler ultrasound (TCD) was used to measure arterial flow velocities at baseline, before and during balloon inflation. The augmented mean flow velocity (MFV), peak systolic velocity (PSV), and end diastolic velocity flow percentages (aMFV%, aPSV%, aEDV%) were calculated and compared based on outcome., Results: Of 11 patients, 3 did not have a temporal window and thus were excluded from our analysis. Six of the remaining 8 patients had middle cerebral artery (MCA) occlusions; the final 2 had terminal internal carotid artery (TICA) occlusions. Three of these 8 patients had good outcome at 90 days (mRS < 3). Before intra-aortic balloon inflation (IABI), the mean affected artery MFV was 23 ± 11 cm/s; during the procedure it was 26 ± 12 cm/s (P = .2). Mean affected artery PSV at baseline and during balloon inflation were 37 ± 16 and 46 ± 23, respectively (P = .1). Mean augmented affected artery MFV% in patients with good long-term outcome was 65.4 ± 46, while the result in those with poor outcome was -3.7 ± 21 (P = .03). Three patients developed anterior cross-filling, and of these 2 had good long-term outcome., Conclusion: TCD monitoring of patients treated with IABI may help in predicting outcome in this novel device., (Copyright © 2012 by the American Society of Neuroimaging.)
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- 2013
- Full Text
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9. The role of transcranial Doppler embolic monitoring in the management of intracranial arterial stenosis.
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Sebastian J, Derksen C, Khan K, and Saqqur M
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- Angiography, Digital Subtraction, Aspirin therapeutic use, Atorvastatin, Blood Flow Velocity, Cerebral Angiography, Clopidogrel, Constriction, Pathologic, Diagnosis, Differential, Female, Heptanoic Acids therapeutic use, Humans, Hydroxymethylglutaryl-CoA Reductase Inhibitors therapeutic use, Intracranial Embolism drug therapy, Ischemic Attack, Transient drug therapy, Magnetic Resonance Imaging, Platelet Aggregation Inhibitors therapeutic use, Pyrroles therapeutic use, Ticlopidine analogs & derivatives, Ticlopidine therapeutic use, Tomography, X-Ray Computed, Young Adult, Intracranial Embolism diagnosis, Ischemic Attack, Transient diagnosis, Ultrasonography, Doppler, Transcranial
- Abstract
Intracranial arterial stenosis (IAS) is thought to be responsible for 8% of all ischemic stroke subtypes. The best medical treatment for this condition is still controversial. Transcranial Doppler (TCD) emboli monitoring may help to guide the treatment by measuring the frequency of microembolic signals (MES). We report a case of IAS where TCD emboli monitoring proved useful in establishing the mechanism of stroke by being artery-to-artery emboli and guiding therapy based on the frequent symptoms and number of MES., (Copyright © 2009 by the American Society of Neuroimaging.)
- Published
- 2011
- Full Text
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