C. Tegeler - Academia.edu (original) (raw)
Papers by C. Tegeler
Acta Neurochirurgica, 2010
In this article, we present our experience with such operations performed under local anaesthesia... more In this article, we present our experience with such operations performed under local anaesthesia. From January 1997 to November 2007, there were 387 patients operated on for asymptomatic carotid stenosis. Patient data were retrospectively evaluated. Thirty-day neurological morbidity and mortality from six different subgroups were analysed and compared. The numbers of perioperative transient ischaemic attacks, as well as surgical and other perioperative complications were also evaluated. Overall morbidity and mortality was 1.8% (seven patients). Stroke was noted in 1.3% (five patients). Transitory ischaemic attacks within the first 30 days were observed in 1.6% (six patients). Only those patients who had intraluminal shunt insertion were found to have significantly higher morbidity and mortality. (p = 0.000018). Myocardial infarction was observed in 0.5% (two patients), one fatal. We have achieved acceptable morbidity and mortality rates (1.8%) according to the parameters set by previous studies such as Asymptomatic Carotid Atherosclerosis Study and Asymptomatic Carotid Stenosis Trial as well as American Heart Association and European Stroke Organisation guidelines. All surgeries were done under local anaesthesia. Shunts were inserted in 22 cases (5.68%).
Journal of Clinical and Experimental Research in Cardiology, 2014
Objective: Longer duration of residence among immigrants to the United States, a proxy measure of... more Objective: Longer duration of residence among immigrants to the United States, a proxy measure of acculturation, has been associated with higher subclinical atherosclerosis. South Asian immigrants are the second fastest growing immigrant group in the U.S. but little is known about the effects of acculturation with atherosclerosis in this high cardiovascular risk population.
The Journal of Clinical Pharmacology, 1991
Dietary supplementation with omega-3 fatty acids reduces platelet aggregation in subjects who usu... more Dietary supplementation with omega-3 fatty acids reduces platelet aggregation in subjects who usually eat a diet low in these fatty acids. Aspirin also has an antiplatelet effect. The clinical effects of the concomitant administration of these agents were examined in this double-blind controlled crossover trial. Twelve healthy adults were randomized to supplement their diet for 21 days with 8 g of omega-3 fatty acids or identical-looking olive oil capsules. At the end of each treatment period, bleeding times were obtained before and after the administration of one 325-mg aspirin tablet. Overall, percent change in bleeding time after omega-3 fatty acid supplementation was significantly prolonged compared with olive oil supplementation before aspirin administration but not after. Bleeding times were influenced significantly by the order of randomization in the two treatment groups. Changes in post-aspirin bleeding time varied in subjects after they received olive oil. Post-aspirin bleeding times after omega-3 fatty acid supplementation were prolonged compared with baseline values but not significantly prolonged when compared with those after olive oil administration. The authors concluded that the concomitant administration of a single dose of aspirin does not prolong bleeding time in subjects who eat a diet enriched by omega-3 fatty acids versus a diet enriched by olive oil.
Circulation Cardiovascular Quality and Outcomes, Apr 1, 2012
Journal of Neuroimaging
ABSTRACT
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1997
To investigate the association of gender, ethnicity, and several cardiovascular risk factors with... more To investigate the association of gender, ethnicity, and several cardiovascular risk factors with carotid artery plaque and plaque with acoustic shadowing in a population-based sample, high-resolution B-mode ultrasonography was used to characterize lesions in the common and internal carotid arteries, and at the carotid bifurcation in 12,796 US men and women, aged 45 to 64 years, participating in the Atherosclerosis Risk in Communities Study (ARIC) baseline survey. In multiple logistic regression analyses, male gender (odds ratio and 95% confidence interval: 1.52 [1.39-1.67]) and increased total (1.47 [1.32-1.63]) and low-density-lipoprotein cholesterol (1.49 [1.34-1.65]) levels were statistically significantly associated only with the presence of plaque. In contradistinction, smoking (2.22 [1.79-2.75]) and hypertension (1.54 [1.30-1.82]) were additionally associated with acoustic shadowing. Hyperfibrinogenemia (1.33 [1.12-1.59]) was associated only with lesions accompanied by acoust...
American journal of medical quality : the official journal of the American College of Medical Quality, Jan 11, 2014
Stroke patients have a high rate of 30-day readmission. Understanding the characteristics of pati... more Stroke patients have a high rate of 30-day readmission. Understanding the characteristics of patients at high risk of readmission is critical. A retrospective case-control study was designed to determine factors associated with 30-day readmission after stroke. A total of 79 cases with acute ischemic or hemorrhagic strokes readmitted to the same hospital within 30 days were compared with 86 frequency-matched controls. Readmitted patients were more likely to have had ≥2 hospitalizations in the year prior to stroke (21.5% vs 2.3% in controls, P < .001), and in the multivariate model, admission National Institutes of Health Stroke Score (NIHSS; odds ratio [OR] = 1.072; 95% confidence interval [CI] = 1.021-1.126 per 1 point increase; P = .005), prior hospitalizations (OR = 2.205; 95% CI = 1.426-3.412 per admission; P < .001), and absence of hyperlipidemia (OR = 0.444; 95% CI = 0.221-0.894; P = .023) were independently associated with readmission. The research team concludes that ad...
Acta neurologica Belgica, 2005
Although abnormalities in course and geometry (tortuosity, kinking, and coiling) of the internal ... more Although abnormalities in course and geometry (tortuosity, kinking, and coiling) of the internal carotid arteries (ICA) are commonly identified, their etiology and relationship with stroke and stroke risk factors remain unclear This study assessed the clinical and ultrasonographic features of the patients with abnormalities in course and geometry of the ICA. Carotid color duplex ultrasound studies of 345 consecutive patients referred to the Neuroultrasound Lab were prospectively evaluated. Abnormalities in direction and course of the ICA were classified according to the criteria of Weibel-Fields and Metz modified by the authors. Kinking was categorized as mild (> 60 degrees), moderate (30 degrees-60 degrees), and severe (< 30 degrees). Carotid abnormalities (CA) were found in 85/345 (24.6%), 60/85 (70.6%) were female. More CA were seen in females older than 60 y/o (p < 0.001), but there was no gender difference in patients 60 y/o or younger CA were bilateral in 41 patients ...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 2000
In this update, the main clinical applications of transcranial Doppler ultrasonography are reasse... more In this update, the main clinical applications of transcranial Doppler ultrasonography are reassessed. A specific format for technology assessment, personal experience, and an extensive review of the literature form the basis of the evaluation. The document is approved by the American Society of Neuroimaging and the Neurosonology Research Group of the World Federation of Neurology.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1991
Cardioembolic mechanisms cause 15 to 20% of all strokes and may account for the high incidence of... more Cardioembolic mechanisms cause 15 to 20% of all strokes and may account for the high incidence of neurological dysfunction associated with cardiopulmonary bypass. Accurate identification of high-risk subjects and/or surgical techniques would allow more effective testing and implementation of preventive or therapeutic measures to help reduce morbidity and mortality. This article reports on validity and reliability testing of a new emboli detection device that allows continuous monitoring of the common carotid artery. The instrument appears to be capable of detecting accurately particles of 193 mu or less in diameter and is highly reliable both within and between observers. In preliminary clinical use, the instrument also detected embolic signals in all patients monitored during cardiopulmonary bypass, while none were detected in healthy control subjects. These results establish the validity and reliability of a new emboli detection device and suggest its potential application to embo...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1993
Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow im... more Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow imaging. Using information contained in the two-dimensional B-mode, gray-scale image to determine velocity, CVI offers potential advantages over Doppler color flow imaging methods. In order to be used clinically, velocity determination with CVI must be validated by other current methods. A Doppler string phantom was studied with a Philips CVI ultrasound system. Velocity measurements were obtained by both CVI and duplex Doppler spectral analysis for constant string speeds from 10 to 200 cm/sec, at intervals of 10 cm/sec. Twenty separate estimates were obtained with each method, at each string speed. Linear regression assessed the relationship between estimated and actual string velocities, with CVI and spectral Doppler analysis yielding highly valid results (CVI = -0.713 + 1.000997 x phantom; r 2 = 0.9979). At all string speeds tested, the averaged estimated and the actual velocities for bo...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1998
Transcranial Doppler ultrasonography (TCD) allows evaluation of blood-flow velocity in intracrani... more Transcranial Doppler ultrasonography (TCD) allows evaluation of blood-flow velocity in intracranial arteries detection and monitoring of vasospasm in patients with subarachnoid hemorrhage. Spectral Doppler artifacts can affect TCD data. A 1-month series of TCD findings showed marked fluctuation in blood-flow velocity values in both the middle and anterior cerebral arteries of a patient with subarachnoid hemorrhage. A mirror-image artifact of the Doppler fast Fourier transform velocity spectrum resulted in erroneous interpretation of higher flow velocity in certain vessels. This artifact may cause misinterpretation of TCD flow-velocity data and lead to improper diagnosis of the condition and treatment of patients.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1998
The case of a patient with temporal lobe hemorrhage is presented. This is the first report of use... more The case of a patient with temporal lobe hemorrhage is presented. This is the first report of use of a new three-dimensional data acquisition system that entails free-hand scanning with three-dimensional transcranial duplex sonography. Three-dimensional image reconstruction reduced the spatial asymmetry inherent in oblique two-dimensional ultrasonography, making evaluation of the precise location, size, and anatomic relations of intracranial hemorrhage easier.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1996
The natural course of ultrasonically detectable microembolism in patients with a symptomatic extr... more The natural course of ultrasonically detectable microembolism in patients with a symptomatic extracranial atherosclerotic lesion is not completely understood. Furthermore, the potential impact of therapeutic management on microemboli detection is anecdotal. A 58-year-old man who experienced a left-hemisphere transient ischemic attack presented with an extracranial ipsilateral high-grade carotid stenosis. He was studied 12 times in 12 months during different medical management, during which time he was symptom free, even though transcranial Doppler evidence of microemboli continued for 5 months.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1996
A variety of disorders affect cerebral hemodynamics. Volume flow rate (VFR) estimates now allow a... more A variety of disorders affect cerebral hemodynamics. Volume flow rate (VFR) estimates now allow accurate quantification of the effect of cerebrovascular lesions on the conduit vessels, with excellent in vivo and in vitro correlation. Four selected cases with VFR data and angiographic correlation are presented to illustrate potential clinical uses of this method. The VFR estimates were obtained with a color M-mode-based velocity imaging technique, which uses time-domain processing (P-700 Color Velocity Imaging System, Philips Ultrasound International, Irvine, CA). In a patient awaiting coronary artery surgery, with unilateral internal carotid artery occlusion and contralateral angiographic stenosis (50-80%, reader variation), the baseline and acetazolamide-challenged common carotid artery VFRs showed excellent conduit function ipsilateral to this stenosis. Thus, the angiographic stenosis did not have significant hemodynamic effects and endarterectomy was avoided. In a patient with an...
Stroke; a journal of cerebral circulation, 1993
The relation between anterior ischemic optic neuropathy and carotid artery atherosclerotic diseas... more The relation between anterior ischemic optic neuropathy and carotid artery atherosclerotic disease is unclear. We studied patients with anterior ischemic optic neuropathy to determine if they had an increased occurrence of carotid artery stenosis. Fifteen consecutive patients with anterior ischemic optic neuropathy were evaluated prospectively for cervical carotid artery stenosis and compared with 30 age- and sex-matched asymptomatic patients and also with 11 age- and sex-matched patients experiencing transient monocular blindness. There was no difference in the mean stenosis of the internal carotid artery between patients with anterior ischemic optic neuropathy (mean carotid stenosis, 19%) and asymptomatic patients (mean carotid stenosis, 9%; p > 0.05), whereas patients with transient monocular blindness had significantly more stenosis (mean, 77%) in the cervical carotid arteries than both control subjects (p < 0.0001) and patients with anterior ischemic optic neuropathy (p &...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1994
A 19-year-old woman with insulin-dependent diabetes mellitus developed pain and tenderness in the... more A 19-year-old woman with insulin-dependent diabetes mellitus developed pain and tenderness in the medial aspect of the left thigh and calf, followed 1 week later by similar symptoms in the right leg. Technetium 99m pyrophosphate (PYP) radionuclide scans showed increased flow and uptake in the medial thigh muscles. Magnetic resonance imaging (MRI) of the thigh showed increased signal on proton density and T2-weighted images in the medial and lateral thigh compartments. High-resolution B-mode ultrasound showed hyperechoic changes in the anteromedial thigh muscles, with loss of normal myofascial interfaces, and a mixed appearance, bilaterally. Two months later, after the symptoms had begun to resolve, the images had improved. This case documents bilateral diabetic thigh infarction identified by abnormal technetium 99m PYP flow studies, MRI signal, and B-mode ultrasound imaging.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1994
Since the introduction of transcranial Doppler sonography in the early 1980s, flow velocity estim... more Since the introduction of transcranial Doppler sonography in the early 1980s, flow velocity estimates have assumed a 0- to 30-degree angle of insonation. Based on limited radiological and anatomical studies, such as assumption appeared justified, and seemed to confer only minimal potential for error due to the cosine function in the Doppler formula. The introduction of transcranial color duplex sonography allows the direct evaluation of this assumption and the effect on flow velocities. Fifteen healthy volunteers were studied bilaterally using a unilateral transtemporal approach from the right. Velocity measurements were taken from the middle, anterior, and posterior cerebral arteries. Flow velocities were obtained with and without angle correction (0 degree). After completion of the color duplex study, velocities were obtained with a conventional, "blind" Doppler transducer at corresponding depths. For all insonated vessels the average angle of insonation was around 30 de...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1995
Ultrasound instruments are used to evaluate blood flow velocities in the human body. Most clinica... more Ultrasound instruments are used to evaluate blood flow velocities in the human body. Most clinical instruments perform velocity calculations based on the Doppler principle and measure the frequency shift of a reflected ultrasound beam. Doppler-only instruments use single-frequency, single-crystal transducers. Linear- and annular-array multiple-crystal transducers are used for duplex scanning (simultaneous B-mode image and Doppler). Clinical interpretation relies primarily on determination of peak velocities or frequency shifts as identified by the Doppler spectrum. Understanding of the validity of these measurements is important for instruments in clinical use. The present study examined the accuracy with which several ultrasound instruments could estimate velocities based on the identification of the peak of the Doppler spectrum, across a range of different angles of insonation, on a Doppler string phantom. The string was running in a water tank at constant speeds of 50, 100, and 1...
Acta Neurochirurgica, 2010
In this article, we present our experience with such operations performed under local anaesthesia... more In this article, we present our experience with such operations performed under local anaesthesia. From January 1997 to November 2007, there were 387 patients operated on for asymptomatic carotid stenosis. Patient data were retrospectively evaluated. Thirty-day neurological morbidity and mortality from six different subgroups were analysed and compared. The numbers of perioperative transient ischaemic attacks, as well as surgical and other perioperative complications were also evaluated. Overall morbidity and mortality was 1.8% (seven patients). Stroke was noted in 1.3% (five patients). Transitory ischaemic attacks within the first 30 days were observed in 1.6% (six patients). Only those patients who had intraluminal shunt insertion were found to have significantly higher morbidity and mortality. (p = 0.000018). Myocardial infarction was observed in 0.5% (two patients), one fatal. We have achieved acceptable morbidity and mortality rates (1.8%) according to the parameters set by previous studies such as Asymptomatic Carotid Atherosclerosis Study and Asymptomatic Carotid Stenosis Trial as well as American Heart Association and European Stroke Organisation guidelines. All surgeries were done under local anaesthesia. Shunts were inserted in 22 cases (5.68%).
Journal of Clinical and Experimental Research in Cardiology, 2014
Objective: Longer duration of residence among immigrants to the United States, a proxy measure of... more Objective: Longer duration of residence among immigrants to the United States, a proxy measure of acculturation, has been associated with higher subclinical atherosclerosis. South Asian immigrants are the second fastest growing immigrant group in the U.S. but little is known about the effects of acculturation with atherosclerosis in this high cardiovascular risk population.
The Journal of Clinical Pharmacology, 1991
Dietary supplementation with omega-3 fatty acids reduces platelet aggregation in subjects who usu... more Dietary supplementation with omega-3 fatty acids reduces platelet aggregation in subjects who usually eat a diet low in these fatty acids. Aspirin also has an antiplatelet effect. The clinical effects of the concomitant administration of these agents were examined in this double-blind controlled crossover trial. Twelve healthy adults were randomized to supplement their diet for 21 days with 8 g of omega-3 fatty acids or identical-looking olive oil capsules. At the end of each treatment period, bleeding times were obtained before and after the administration of one 325-mg aspirin tablet. Overall, percent change in bleeding time after omega-3 fatty acid supplementation was significantly prolonged compared with olive oil supplementation before aspirin administration but not after. Bleeding times were influenced significantly by the order of randomization in the two treatment groups. Changes in post-aspirin bleeding time varied in subjects after they received olive oil. Post-aspirin bleeding times after omega-3 fatty acid supplementation were prolonged compared with baseline values but not significantly prolonged when compared with those after olive oil administration. The authors concluded that the concomitant administration of a single dose of aspirin does not prolong bleeding time in subjects who eat a diet enriched by omega-3 fatty acids versus a diet enriched by olive oil.
Circulation Cardiovascular Quality and Outcomes, Apr 1, 2012
Journal of Neuroimaging
ABSTRACT
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1997
To investigate the association of gender, ethnicity, and several cardiovascular risk factors with... more To investigate the association of gender, ethnicity, and several cardiovascular risk factors with carotid artery plaque and plaque with acoustic shadowing in a population-based sample, high-resolution B-mode ultrasonography was used to characterize lesions in the common and internal carotid arteries, and at the carotid bifurcation in 12,796 US men and women, aged 45 to 64 years, participating in the Atherosclerosis Risk in Communities Study (ARIC) baseline survey. In multiple logistic regression analyses, male gender (odds ratio and 95% confidence interval: 1.52 [1.39-1.67]) and increased total (1.47 [1.32-1.63]) and low-density-lipoprotein cholesterol (1.49 [1.34-1.65]) levels were statistically significantly associated only with the presence of plaque. In contradistinction, smoking (2.22 [1.79-2.75]) and hypertension (1.54 [1.30-1.82]) were additionally associated with acoustic shadowing. Hyperfibrinogenemia (1.33 [1.12-1.59]) was associated only with lesions accompanied by acoust...
American journal of medical quality : the official journal of the American College of Medical Quality, Jan 11, 2014
Stroke patients have a high rate of 30-day readmission. Understanding the characteristics of pati... more Stroke patients have a high rate of 30-day readmission. Understanding the characteristics of patients at high risk of readmission is critical. A retrospective case-control study was designed to determine factors associated with 30-day readmission after stroke. A total of 79 cases with acute ischemic or hemorrhagic strokes readmitted to the same hospital within 30 days were compared with 86 frequency-matched controls. Readmitted patients were more likely to have had ≥2 hospitalizations in the year prior to stroke (21.5% vs 2.3% in controls, P < .001), and in the multivariate model, admission National Institutes of Health Stroke Score (NIHSS; odds ratio [OR] = 1.072; 95% confidence interval [CI] = 1.021-1.126 per 1 point increase; P = .005), prior hospitalizations (OR = 2.205; 95% CI = 1.426-3.412 per admission; P < .001), and absence of hyperlipidemia (OR = 0.444; 95% CI = 0.221-0.894; P = .023) were independently associated with readmission. The research team concludes that ad...
Acta neurologica Belgica, 2005
Although abnormalities in course and geometry (tortuosity, kinking, and coiling) of the internal ... more Although abnormalities in course and geometry (tortuosity, kinking, and coiling) of the internal carotid arteries (ICA) are commonly identified, their etiology and relationship with stroke and stroke risk factors remain unclear This study assessed the clinical and ultrasonographic features of the patients with abnormalities in course and geometry of the ICA. Carotid color duplex ultrasound studies of 345 consecutive patients referred to the Neuroultrasound Lab were prospectively evaluated. Abnormalities in direction and course of the ICA were classified according to the criteria of Weibel-Fields and Metz modified by the authors. Kinking was categorized as mild (> 60 degrees), moderate (30 degrees-60 degrees), and severe (< 30 degrees). Carotid abnormalities (CA) were found in 85/345 (24.6%), 60/85 (70.6%) were female. More CA were seen in females older than 60 y/o (p < 0.001), but there was no gender difference in patients 60 y/o or younger CA were bilateral in 41 patients ...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 2000
In this update, the main clinical applications of transcranial Doppler ultrasonography are reasse... more In this update, the main clinical applications of transcranial Doppler ultrasonography are reassessed. A specific format for technology assessment, personal experience, and an extensive review of the literature form the basis of the evaluation. The document is approved by the American Society of Neuroimaging and the Neurosonology Research Group of the World Federation of Neurology.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1991
Cardioembolic mechanisms cause 15 to 20% of all strokes and may account for the high incidence of... more Cardioembolic mechanisms cause 15 to 20% of all strokes and may account for the high incidence of neurological dysfunction associated with cardiopulmonary bypass. Accurate identification of high-risk subjects and/or surgical techniques would allow more effective testing and implementation of preventive or therapeutic measures to help reduce morbidity and mortality. This article reports on validity and reliability testing of a new emboli detection device that allows continuous monitoring of the common carotid artery. The instrument appears to be capable of detecting accurately particles of 193 mu or less in diameter and is highly reliable both within and between observers. In preliminary clinical use, the instrument also detected embolic signals in all patients monitored during cardiopulmonary bypass, while none were detected in healthy control subjects. These results establish the validity and reliability of a new emboli detection device and suggest its potential application to embo...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1993
Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow im... more Color velocity imaging (CVI) is a new non-Doppler ultrasound technique for vascular color flow imaging. Using information contained in the two-dimensional B-mode, gray-scale image to determine velocity, CVI offers potential advantages over Doppler color flow imaging methods. In order to be used clinically, velocity determination with CVI must be validated by other current methods. A Doppler string phantom was studied with a Philips CVI ultrasound system. Velocity measurements were obtained by both CVI and duplex Doppler spectral analysis for constant string speeds from 10 to 200 cm/sec, at intervals of 10 cm/sec. Twenty separate estimates were obtained with each method, at each string speed. Linear regression assessed the relationship between estimated and actual string velocities, with CVI and spectral Doppler analysis yielding highly valid results (CVI = -0.713 + 1.000997 x phantom; r 2 = 0.9979). At all string speeds tested, the averaged estimated and the actual velocities for bo...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1998
Transcranial Doppler ultrasonography (TCD) allows evaluation of blood-flow velocity in intracrani... more Transcranial Doppler ultrasonography (TCD) allows evaluation of blood-flow velocity in intracranial arteries detection and monitoring of vasospasm in patients with subarachnoid hemorrhage. Spectral Doppler artifacts can affect TCD data. A 1-month series of TCD findings showed marked fluctuation in blood-flow velocity values in both the middle and anterior cerebral arteries of a patient with subarachnoid hemorrhage. A mirror-image artifact of the Doppler fast Fourier transform velocity spectrum resulted in erroneous interpretation of higher flow velocity in certain vessels. This artifact may cause misinterpretation of TCD flow-velocity data and lead to improper diagnosis of the condition and treatment of patients.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1998
The case of a patient with temporal lobe hemorrhage is presented. This is the first report of use... more The case of a patient with temporal lobe hemorrhage is presented. This is the first report of use of a new three-dimensional data acquisition system that entails free-hand scanning with three-dimensional transcranial duplex sonography. Three-dimensional image reconstruction reduced the spatial asymmetry inherent in oblique two-dimensional ultrasonography, making evaluation of the precise location, size, and anatomic relations of intracranial hemorrhage easier.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1996
The natural course of ultrasonically detectable microembolism in patients with a symptomatic extr... more The natural course of ultrasonically detectable microembolism in patients with a symptomatic extracranial atherosclerotic lesion is not completely understood. Furthermore, the potential impact of therapeutic management on microemboli detection is anecdotal. A 58-year-old man who experienced a left-hemisphere transient ischemic attack presented with an extracranial ipsilateral high-grade carotid stenosis. He was studied 12 times in 12 months during different medical management, during which time he was symptom free, even though transcranial Doppler evidence of microemboli continued for 5 months.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1996
A variety of disorders affect cerebral hemodynamics. Volume flow rate (VFR) estimates now allow a... more A variety of disorders affect cerebral hemodynamics. Volume flow rate (VFR) estimates now allow accurate quantification of the effect of cerebrovascular lesions on the conduit vessels, with excellent in vivo and in vitro correlation. Four selected cases with VFR data and angiographic correlation are presented to illustrate potential clinical uses of this method. The VFR estimates were obtained with a color M-mode-based velocity imaging technique, which uses time-domain processing (P-700 Color Velocity Imaging System, Philips Ultrasound International, Irvine, CA). In a patient awaiting coronary artery surgery, with unilateral internal carotid artery occlusion and contralateral angiographic stenosis (50-80%, reader variation), the baseline and acetazolamide-challenged common carotid artery VFRs showed excellent conduit function ipsilateral to this stenosis. Thus, the angiographic stenosis did not have significant hemodynamic effects and endarterectomy was avoided. In a patient with an...
Stroke; a journal of cerebral circulation, 1993
The relation between anterior ischemic optic neuropathy and carotid artery atherosclerotic diseas... more The relation between anterior ischemic optic neuropathy and carotid artery atherosclerotic disease is unclear. We studied patients with anterior ischemic optic neuropathy to determine if they had an increased occurrence of carotid artery stenosis. Fifteen consecutive patients with anterior ischemic optic neuropathy were evaluated prospectively for cervical carotid artery stenosis and compared with 30 age- and sex-matched asymptomatic patients and also with 11 age- and sex-matched patients experiencing transient monocular blindness. There was no difference in the mean stenosis of the internal carotid artery between patients with anterior ischemic optic neuropathy (mean carotid stenosis, 19%) and asymptomatic patients (mean carotid stenosis, 9%; p > 0.05), whereas patients with transient monocular blindness had significantly more stenosis (mean, 77%) in the cervical carotid arteries than both control subjects (p < 0.0001) and patients with anterior ischemic optic neuropathy (p &...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1994
A 19-year-old woman with insulin-dependent diabetes mellitus developed pain and tenderness in the... more A 19-year-old woman with insulin-dependent diabetes mellitus developed pain and tenderness in the medial aspect of the left thigh and calf, followed 1 week later by similar symptoms in the right leg. Technetium 99m pyrophosphate (PYP) radionuclide scans showed increased flow and uptake in the medial thigh muscles. Magnetic resonance imaging (MRI) of the thigh showed increased signal on proton density and T2-weighted images in the medial and lateral thigh compartments. High-resolution B-mode ultrasound showed hyperechoic changes in the anteromedial thigh muscles, with loss of normal myofascial interfaces, and a mixed appearance, bilaterally. Two months later, after the symptoms had begun to resolve, the images had improved. This case documents bilateral diabetic thigh infarction identified by abnormal technetium 99m PYP flow studies, MRI signal, and B-mode ultrasound imaging.
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1994
Since the introduction of transcranial Doppler sonography in the early 1980s, flow velocity estim... more Since the introduction of transcranial Doppler sonography in the early 1980s, flow velocity estimates have assumed a 0- to 30-degree angle of insonation. Based on limited radiological and anatomical studies, such as assumption appeared justified, and seemed to confer only minimal potential for error due to the cosine function in the Doppler formula. The introduction of transcranial color duplex sonography allows the direct evaluation of this assumption and the effect on flow velocities. Fifteen healthy volunteers were studied bilaterally using a unilateral transtemporal approach from the right. Velocity measurements were taken from the middle, anterior, and posterior cerebral arteries. Flow velocities were obtained with and without angle correction (0 degree). After completion of the color duplex study, velocities were obtained with a conventional, "blind" Doppler transducer at corresponding depths. For all insonated vessels the average angle of insonation was around 30 de...
Journal of neuroimaging : official journal of the American Society of Neuroimaging, 1995
Ultrasound instruments are used to evaluate blood flow velocities in the human body. Most clinica... more Ultrasound instruments are used to evaluate blood flow velocities in the human body. Most clinical instruments perform velocity calculations based on the Doppler principle and measure the frequency shift of a reflected ultrasound beam. Doppler-only instruments use single-frequency, single-crystal transducers. Linear- and annular-array multiple-crystal transducers are used for duplex scanning (simultaneous B-mode image and Doppler). Clinical interpretation relies primarily on determination of peak velocities or frequency shifts as identified by the Doppler spectrum. Understanding of the validity of these measurements is important for instruments in clinical use. The present study examined the accuracy with which several ultrasound instruments could estimate velocities based on the identification of the peak of the Doppler spectrum, across a range of different angles of insonation, on a Doppler string phantom. The string was running in a water tank at constant speeds of 50, 100, and 1...