Biomedical subjects

C H Tegeler

Publications and source records attributed to C H Tegeler.

At least 19 recordsLinked to original sources

PubMed1999

A new dynamic method for detection of internal jugular valve incompetence using air contrast ultrasonography.

The internal jugular (IJ) valve is the only valve between the heart and the brain, preventing venous reflux into the IJ vein. Internal jugular valve competence has been tested by IJ venography. Doppler ultrasonography of the IJ vein and M-mode ultrasonography of the IJ valve, and color flow imaging (CFI) of the IJ vein. However, interpretation of venous Doppler and CFI is difficult, and venography is invasive. The purpose of this study was to evaluate the feasibility of a new dynamic method to test IJ valve competency, and to review the literature regarding the potential clinical importance of this pathophysiology. Ten patients had intravenous injection of agitated air and saline during Valsalva maneuver with B-mode monitoring and CFI of the right IJ vein. Contrast bubbles were clearly identified refluxing into the right IJ vein in 50% of patients. Air contrast studies more often showed IJ valve incompetence than CFI. Bubbles appeared in the IJ vein within 19.2 sec and persisted up to 282 sec. Bubble aggregation was also observed. There was no correlation between positive bubbles and the presence of spontaneous echo contrast on baseline B-mode imaging. Air contrast ultrasound venography (ACUV) is a new noninvasive method to assess competency of the IJ valves. This technique is feasible, appears to be more sensitive than CFI, and adds a new dimension to the study of the venous system in cerebrovascular disease. Potential clinical application includes evaluation of patients with increased central venous pressure, those with morning headaches, and those on positive end-expiratory pressure ventilators.

Aged↗

PubMed1998

Vagus nerve imaging with ultrasound: anatomic and in vivo validation.

To provide the anatomic basis and demonstrate the reproducibility of ultrasound studies for the identification of the vagus nerve within its course in the carotid sheath in the neck, cadaveric and in vivo imaging studies were conducted. On transverse B-mode images of the neck, there is a centrally hypoechoic and peripherally hyperechoic structure between the common carotid artery and the jugular vein inside the carotid sheath. This structure was also identified in a fresh, nonpreserved cadaver and was marked with a hypodermic needle by means of a transdermal approach. Neck dissection was performed leaving the carotid sheath intact. B-mode imaging yielded detailed anatomic information about the structures in the carotid sheath. Further dissection showed the vagus nerve as the target of the needle. One hundred consecutive transverse carotid scans were reviewed, and the characteristic echo patterns of the vagus nerve were identified in 97 instances. A distinct and reproducible, round, hypoechoic structure was defined adjacent to the common carotid artery and jugular vein as the vagus nerve. On the basis of this study, a new, noninvasive, and highly reproducible method to locate the vagus nerve in the carotid sheath is introduced. This may lead to further clinical application such as presurgical localization or ultrasound-guided needle studies. Stimulation of the vagus nerve has been proposed for seizure therapy. The diagnosis of vagus nerve tumors may be improved.

Humans↗

PubMed1998

Mirror-image artifact can affect transcranial Doppler interpretation.

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.

Aneurysm, Ruptured↗

PubMed1997

[Neuro-ultrasonographic evaluation of ischemic stroke].

INTRODUCTION AND DEVELOPMENT: The development of new management strategies for acute stroke demands better understanding of the ischemic mechanism, cerebrovascular anatomy, and cerebral hemodynamics for individual patients. The use of carotid duplex sonography, transcranial Doppler sonography, and echocardiography allows evaluation of the key areas of interest in a prompt, safe, accurate, and cost effective manner. CONCLUSIONS: Knowledge of these methods is essential for neurologist caring for patients with stroke.

Brain Ischemia↗

PubMed1996

[Volume flow in carotid occlusion. Measurement using ultrasound time domains and color M mode analysis].

AIM: To quantify the volume flow rate- (VFR-) effects of internal carotid disease on the common carotid artery both ipsi- and contralaterally for various degrees of stenosis. METHOD: A non-invasive ultrasonic time domain processing (M-mode) was used. This proved to be reproducible in vivo and accurate in vitro. 109 patients (mean age 66.7 yrs.) having at least 50% stenosis of the internal carotid artery or a cerebral ischaemia were studied. The haemodynamic effect of the stenosis on the entire anterior brain circulation supplied by the carotid artery was assessed. Stenoses were graded in 4 groups. RESULTS: Significant VFR reduction occurred ipsilaterally in high grade (75-94%) stenosis and occlusion of the internal carotid artery, but not with moderate (50-74%) stenosis (p < 0.05). Ipsilaterally to stenoses there was a decrease in VFR, which was more marked in higher than in lower grade stenoses. Contralaterally there was an increase in VFR. These groups differed in a statistically significant way (p < 0.05). CONCLUSION: This ultrasonic VFR method demonstrates the flow effect of carotid stenoses both ipsi- and contralaterally and adds to the understanding of the haemodynamics in individual patients.

Adult↗

PubMed1996

Clinical cerebrovascular applications of arterial ultrasound volume flow rate estimates.

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 arteriovenous malformation fed by the left vertebral and left external carotid arteries, high in the left cervical region, VFR estimates of two to three times normal predicted the feeding vessels, influenced management, and proved helpful in follow-up. In a patient with subclavian steal syndrome, VFR estimates quantified the steal after brachial hyperemia. Finally, in a patient with delayed vasoconstriction after subarachnoid hemorrhage, very low VFR estimates preceded clinical deterioration. Quantification of hemodynamic changes with VFR estimates was useful for the diagnosis, management, and follow-up of these patients with four types of cerebrovascular disease, and should be applicable in many others.

Adult↗

PubMed1996

Middle cerebral artery velocity correlates with nitroglycerin-induced headache onset.

Headache often accompanies treatment with nitroglycerin, but the cerebral hemodynamic effects and the exact mechanism of the headache are incompletely understood. Transcranial Doppler monitoring allows evaluation and monitoring of changes in blood flow velocity in the large intracranial arteries. The objective of this study was to assess middle cerebral artery (MCA) blood flow velocities with transcranial Doppler monitoring in subjects receiving continuous low-dose nitroglycerin intravenously or by patch, and correlate these with clinical headache. Twenty-eight normal adult men received nitroglycerin (0.12 micrograms/kg/min intravenously [n = 14] or 0.6 mg/min by transdermal patch [n = 14]), for up to 120 minutes, with monitoring of clinical headache status (standard 4-point scale), blood pressure, heart rate, end-expiratory PCO2 (CO2), and right MCA velocity. All subjects developed headache (mean time to onset, 34 min), reaching moderate or severe levels in 20. There were no differences in age, weight, mean blood pressure, mean heart rate, or resting end-tidal CO2 between those whose headache reached a moderate to severe level and those whose headache remained mild. MCA velocity decreased from baseline values at all levels of clinical headache (onset, -17%; moderate, -18%; severe, -16%; nitroglycerin stopped, -19%) (p, 0.0001 by t test for each stage of headache). MCA velocity remained decreased at the time of headache resolution (-14%; p < 0.001). Blood pressure, heart rate, and CO2 did not change significantly. There were no differences related to route of nitroglycerin dosing. These data show that continuous low doses of nitroglycerin by patch or intravenously produce headache in normal male subjects. MCA velocities were significantly decreased at headache onset and at all levels of headache severity. Changes in MCA velocity persisted beyond the clinical headache. These results suggest a direct MCA vasodilatory effect of nitroglycerin. This method may also be used to evaluate the intracranial hemodynamic effects of other vasoactive drugs, even in clinical settings.

Administration, Cutaneous↗

PubMed1996

Serial transcranial Doppler monitoring after transient ischemic attack.

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.

Anticoagulants↗

PubMed1995

Experimental aspects of high-intensity transient signals in the detection of emboli.

Experimental studies in the 1960s and 1970s demonstrated the high sensitivity of Doppler ultrasound in detecting gaseous bubbles. More recent studies have shown that microscopic air bubbles, as well as glass microspheres as small as 5 mu to 20 mu, cause characteristic high-intensity signals. Recently it has been demonstrated that less echogenic embolic materials such as thrombus, platelet aggregates, and atheroma can also be detected with a high sensitivity. Such "solid," or formed-element, emboli as small as 200 mu to 400 mu can be detected; the lower size limit of detection was due to an inability to make smaller embolic particles rather than to the sensitivity of the detection process itself. Analysis of the Doppler signals provides some information about embolus size and composition, but accurate characterization in clinical practice is not possible using current technology. Studies in experimental models have allowed the detailed description of embolic signals; they appear as a short-duration, frequency-focused increase in intensity, predominantly unidirectional in the direction of flow, and usually contained within the spectral envelope. In contrast, artifacts appear as a bidirectional, high-intensity increase with maximum intensity at low frequencies. These differences have been exploited to develop automatic embolus detection programs, and an off-line version has been successfully validated in an experimental model.

Animals↗

PubMed1995

Peak velocity overestimation and linear-array spectral Doppler.

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 150 cm/sec and also in a sine wave pattern at 100- or 150-cm/sec amplitude. Angles of insonation were 30, 45, 60, and 70 degrees. The single-frequency, single-crystal transducers (PC Dop 842, 2-MHz pulsed-wave, 4-MHz continuous-wave) provided acceptably accurate velocity estimates at all tested velocities independent of the angle of insonation. All duplex Doppler instruments with linear-array transducers (Philips P700, 5.0-MHz; Hewlett-Packard Sonos 1000, 7.5-MHz; ATL Ultramark 9 HDI, 7.5-MHz) exhibited a consistent overestimation of the true flow velocity due to increasing intrinsic spectral broadening with increasing angle of insonation.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗

PubMed1995

Ultrasonography for diagnosis and management of carotid artery atherosclerosis. A position paper of the American Society of Neuroimaging.

The importance of identifying patients with carotid artery stenosis has attained greater significance in light of recent treatment trials of the efficacy of medical and surgical treatment of both symptomatic and asymptomatic carotid stenosis. Doppler and B-mode ultrasonography can accurately diagnose and quantify stenosis at the cervical carotid artery bifurcation. The development of duplex color-flow instruments has enhanced the sensitivity and specificity of this examination. Ultrasonography should be employed as an initial examination to identify patients with carotid artery stenosis and determine whether further evaluation or treatment is necessary.

Blood Flow Velocity↗

PubMed1995

Left dural to right cavernous sinus fistula. A case report.

Direct carotid-cavernous sinus fistulas that present with signs and symptoms contralateral to the arterial supply of the fistulas are not uncommon. We present a thoroughly documented case of a dural-cavernous sinus fistula with symptoms exclusively contralateral to the arterial source, a rarer entity. The patient presented with a red, proptotic right eye and a history of transient horizontal diplopia and a "feeling of fullness" in that eye. Magnetic resonance imaging (MRI) of the brain and orbits performed at another hospital had shown no abnormalities. Carotid angiography performed on the right side was normal; carotid angiography performed on the left side showed a dural-cavernous sinus fistula, with shunting from branches of the left external carotid artery directly to the right cavernous sinus. Orbital duplex color-flow sonography showed reverse flow in a dilated right superior ophthalmic vein. This unusual manifestation of a dural-cavernous sinus fistula offers insight into the pathophysiology of arteriovenous fistulas involving the cavernous sinus, and is a reminder that bilateral injections are required when performing carotid angiography to characterize these disorders.

Angiography↗

PubMed1994

Carotid stenosis in patients with atrial fibrillation. Prevalence, risk factors, and relationship to stroke in the Stroke Prevention in Atrial Fibrillation Study.

BACKGROUND: Several mechanisms contribute to the increased stroke rate of patients with atrial fibrillation (AF). We assessed the frequency of carotid artery stenosis in patients with AF and its relationship to stroke during aspirin or warfarin therapy. METHODS: Carotid ultrasonography was done in 676 patients with AF enrolled in the Stroke Prevention in Atrial Fibrillation Study to detect cervical carotid stenosis of 50% or more of the luminal diameter. The presence of carotid stenosis was correlated with patient features and subsequent stroke during a mean of 2.6 years of follow-up. RESULTS: In patients with AF who were older than 70 years, the frequency of carotid stenosis was 12% in men and 11% in women. Carotid stenosis was independently associated with systolic hypertension (relative risk, 2.4; P = .002), diabetes (relative risk, 1.8; P = .04), and tobacco use (relative risk, 1.8; P = .02). Carotid stenosis did not add significantly to prediction of stroke when analyzed with other clinical risk factors for stroke in patients with AF (relative risk, 1.3; 95% confidence interval, 0.5 to 3.6; P = .55). CONCLUSIONS: Carotid artery stenosis of 50% or more occurs in about 12% of elderly patients with AF, reflecting the substantial prevalence of hypertension and diabetes in these patients. Carotid stenosis was not usefully predictive of stroke in patients with AF who were given aspirin or warfarin. Routine ultrasonography to detect carotid stenosis does not appear warranted in patients with AF without previous symptoms of brain ischemia.

Aged↗

PubMed1994

Angle correction in transcranial Doppler sonography.

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 degrees. However, there was a wide variability of individual angles of insonation (0-70 degrees) in specific vessels. In 74.5% of all vessels, the angle-corrected flow velocity did not exceed the uncorrected velocity by more than 25%. In 14.5% the angle-corrected velocity was 25 to 50% higher and in 10.8% it was more than 50% higher as compared to the uncorrected velocity. Thus, the angle of insonation was unpredictable and often higher than originally expected. Angle-corrected velocities were higher than uncorrected values, and were more than 25% higher in about one-fourth of the vessels studied. Understanding of the clinical importance of such differences requires further study.

Adult↗

PubMed1994

Control for carbon dioxide-related changes in flow velocity by transcranial Doppler monitoring.

Transcranial Doppler ultrasonography can monitor changes in intracranial blood flow velocity over time in a variety of experimental and clinical settings with excellent temporal resolution. Alterations in arterial carbon dioxide pressure exert a profound influence on blood flow velocity. Such changes exhibit important individual fluctuation depending on respiratory status. This limits the ability of transcranial Doppler to accurately study subtle changes in blood flow velocity, independent of the respiratory state of the subject. Suggested here is a method to control for the respiration artifact on blood flow velocity. The middle cerebral artery of 7 healthy male volunteers was studied with transcranial Doppler under resting conditions, monitoring end-tidal carbon dioxide concentration and blood flow velocity. Hyperventilation was performed both voluntarily and with pharmacological induction by human corticotropin-releasing hormone. These studies were carried out both with and without the use of counterregulation of the end-tidal carbon dioxide concentration via a respiration unit, with an adjustable carbon dioxide-oxygen gas supply preventing significant changes in end-tidal carbon dioxide. The blood flow velocity in the middle cerebral artery during maximal voluntary hyperventilation decreased from baseline values of 100% to 44.4 +/- 4.3% (a 55.6% decrease), and with human corticotropin-releasing hormone-induced involuntary hyperventilation, to 65.1 +/- 5.3% (a 34.9% decrease). With the control method, blood flow velocities during voluntary and pharmacological hyperventilation were 100 +/- 1.6% and 100 +/- 2.8%, respectively. This method allows for control of respiration-induced artifacts during transcranial Doppler monitoring, and can be used to assess the effect of direct or indirect blood flow velocity stimuli independent of respiratory status.

Adult↗

PubMed1993

In vitro validation of color velocity imaging and spectral Doppler for velocity determination.

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 both methods were within the 95% confidence estimates. The range for the CVI 95% confidence limits from the regression line varied from +/-1.07 cm/sec at the lowest speed of 10 cm/sec (11.6%) to +/-7.72 cm/sec at 200 cm/sec (3.87%). Based on in vitro testing, CVI is as accurate as Doppler spectral analysis for the estimation of flow velocity.

Blood Flow Velocity↗

PubMed1993

The transcranial Doppler standardization project. Phase 1 results. The TCD Study Group, American Society of Neuroimaging.

A project to pursue standardization of the performance and interpretation of transcranial Doppler studies was designed. Phase I consisted of a national survey of the current practice of transcranial Doppler in the United States. From 200 ultrasound laboratories surveyed about the use of transcranial Doppler, 60 completed questionnaires were returned. The results show that further standardization of transcranial Doppler performance and interpretation is necessary, and provide the foundation for phases II and III of the project.

Brain Diseases↗

PubMed1993

Transcranial Doppler validation pilot study.

The use of transcranial Doppler sonography (TCD) for the evaluation of patients with ischemic cerebrovascular disease remains controversial. This study was organized to gather preliminary data regarding the sensitivity and specificity of TCD when compared to cerebral angiography in detecting stenosing lesions and collateral flow patterns of the anterior cerebral circulation. Forty-two patients from six medical centers were prospectively enrolled. Each received cerebral angiography and TCD testing within 24 hours of each other. Based on TCD criteria established a priori, the results were first analyzed by a blinded investigator and then by computer. Computerized analyses were then repeated with modified criteria. Collateral flow through the anterior communicating and ophthalmic arteries was detected with sensitivities of 62% and 100%, and specificities of 98% and 92%, respectively. Internal carotid artery proximal and distal severe ( greater than 70%) stenoses were detected with sensitivities of 79% and 100% and specificities of 88% and 97%. Middle and anterior cerebral artery stenoses and middle cerebral artery occlusion were detected with specificities exceeding 98%; however, the data were insufficient to determine sensitivity. Computerized analyses did not permit improvement of sensitivity and specificity of the baseline criteria. The selected TCD criteria are highly specific in detecting intracranial stenoses and collateral flow patterns of the anterior circulation. The criteria have limited but acceptable sensitivity and specificity in detecting internal carotid artery origin severe stenoses, and are highly sensitive in detecting ophthalmic artery retrograde flow. A study with a larger sample is necessary to provide definitive guidelines for diagnosis.

Adult↗