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Biomedical subjects

D E Strandness

Publications and source records attributed to D E Strandness.

At least 325 records · Page 18Linked to original sources
PubMedDate not supplied

Peripheral arterial duplex scanning.

Recent improvements in duplex ultrasound technology now permit the application of duplex ultrasound to the assessment of arterial occlusive disease from the level of the aorta to the popliteal trifurcation. In our laboratory we have developed duplex waveform criteria for classifying peripheral arterial stenosis into one of five categories: normal, 1%-19% stenosis, 20%-49% stenosis, 50%-99% stenosis and occlusion. When prospectively compared with angiography the duplex examination has a 77% sensitivity and a 98% specificity in determining the presence of a hemodynamically significant lesion (greater than 50% stenosis). The examination can be used clinically to give hemodynamic information about specific arterial lesions, as a screening procedure prior to angiography or angioplasty and as a means of following the results of peripheral arterial surgery and dilatations.

Arterial Occlusive Diseases↗
PubMedDate not supplied

Techniques for high-resolution MR imaging of atherosclerotic plaque.

Atherosclerotic cardiovascular disease is the most common cause of death in the United States. Investigation of atherosclerotic plaque morphology and composition is important because the findings may be useful in predicting prognosis or response to therapy. This study presents high-resolution magnetic resonance (MR) imaging techniques developed on a 1.5-T whole-body imager with a custom-built surface coil, for characterizing the composition and morphology of plaque removed at carotid endarterectomy. The initial comparison of MR imaging and histologic results showed good correlation. In conjunction with MR angiography, these techniques could be used in in vivo imaging to define the size, location, and contents of atherosclerotic plaque at the carotid bifurcation.

Artifacts↗
PubMedDate not supplied

Phased-array magnetic resonance imaging of the carotid artery bifurcation: preliminary results in healthy volunteers and a patient with atherosclerotic disease.

A high resolution MR imaging technique using a custom designed flexible phased-array surface coil was developed to examine the wall of the carotid artery bifurcation in vivo. The phased-array consisted of two overlapping coils which increased the image signal-to-noise ratio at the depth of the carotid artery by approximately 70%, relative to a similarly sized single loop coil. The imaging protocol included a 2D T1-weighted (T1W) spin-echo scan and cardiac gated T2-weighted and proton density-weighted (PDW) fast spin-echo (FSE) scans. Images were obtained of six healthy volunteers and of one patient with known atherosclerotic disease several days before carotid endarterectomy. On T1W and PDW images of the healthy volunteers, the carotid arterial wall appeared to be comprised of two concentric rings; a high signal inner ring and a lower signal outer ring. The MR images of the patient revealed a calcified carotid bifurcation plaque which was confirmed during surgery. The endarterectomy specimen was imaged in vitro with MR and then sectioned histologically for correlation with the patients in vivo images. Our preliminary findings indicate that a high resolution technique may provide a noninvasive technique to study atherosclerosis of the carotid bifurcation.

Arteriosclerosis↗
PubMedDate not supplied

Atherosclerosis of the carotid artery: evaluation by magnetic resonance angiography.

Carotid artery atherosclerotic plaques (APs) can lead to brain ischemia, an event shown to correlate with both the degree of stenosis and the composition of the AP. Currently, accurate estimates of stenosis can be obtained by either x-ray angiography or three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA). Our purpose was to determine whether three-dimensional TOF MRA images could also provide information on plaque location, morphology, and composition. Seven pre-endarterectomy patients underwent three-dimensional TOF MRA. After endarterectomy, plaque histology was evaluated. Three-dimensional TOF MRA images contained sufficient soft tissue contrast to differentiate the plaques from the surrounding tissues in all cases. Estimation of plaque morphology had 80% correlation with histology. Finally, intraplaque hemorrhage and calcification were deplicted as regions of moderately high and very low intensity, respectively. These preliminary results suggest that three-dimensional TOF MRA may be useful in studying the development and progression of carotid atherosclerosis.

Aged↗
PubMedDate not supplied

Flow velocity patterns in the carotid bifurcations of young, presumed normal subjects.

Spectral analysis of pulsed Doppler velocity waveforms has been found useful as a diagnostic technique in the assessment of carotid artery disease. While spectral broadening of the velocity waveform obtained at center stream sites is usually associated with arterial disease, the present study describes spectral patterns resulting from disturbed blood flow in the proximal branches of the carotid bifurcation in young, presumed normal human subjects. In those studied, spectral patterns in the bifurcation region exhibit characteristics similar to those occurring in zones of flow separation in model studies under conditions of steady flow. It is important to distinguish the spectral patterns due to arterial disease from those occurring in the normal bifurcation. This paper describes the types of flow disturbances noted in presumed normal arteries and points out the need to understand the flow velocity patterns that may be found at specific anatomical sites across the carotid bifurcation.

Adult↗
PubMedDate not supplied

Evaluating carotid artery disease. The concordance between pulsed Doppler/spectrum analysis and angiography.

The results of ultrasonic pulsed Doppler duplex scanning with spectral analysis and computer pattern recognition are compared with the results of contrast arteriography in patients screened for extracranial carotid artery disease. The intraangiographer variability (one radiologist reading the same films twice) and the interangiographer variability (two radiologists reading the same film independently) were also studied. To calculate degrees of agreement corrected for chance, the Kappa statistic was computed for all the evaluation methods employed. At the present time, the concordance between spectral analysis and cerebral contrast angiography reaches a Kappa value of 0.682 +/- 0.064. This level of agreement compares favorably with the interangiographer agreement level (K = 0.568 +/- 0.058) and the intraangiographer agreement (K = 0.711 +/- 0.054). The computer pattern recognition program predicted the degree of stenosis by angiography with an agreement of K = 0.721 +/- 0.059. This concordance compares favorably to that observed when the radiologists are compared with themselves and is greater than that reached by two different radiologists. The continuous improvement in precision and accuracy of duplex scanning offers the promise of its usefulness in clinical and epidemiological studies.

Blood Flow Velocity↗
PubMedDate not supplied

Post-endarterectomy carotid ultrasonic duplex scanning concordance with contrast angiography.

The results of ultrasonic duplex scanning combined with spectral analysis are compared with the results of contrast angiography in patients after endarterectomy in which recurrence of carotid arterial disease was suspected. Thirty-six patients underwent a duplex scan study within 3 months of their post-operative angiogram, performed at their physician's discretion (44 studies). The overall accuracy of the method was 80%. Our ability to predict a greater than 50% diameter reduction along with total occlusion was 94%. The measure of agreement corrected for chance between arteriography and duplex scanning as expressed by the Kappa statistic was 0.675 +/- SE (K) 0.096. This level of agreement compared favorably to that of inter- and intra-observer variability in reading cerebral angiograms. The accuracy reported justifies the clinical use of ultrasonic duplex scanning in the detection of recurrent stenosis after carotid endarterectomy.

Blood Flow Velocity↗
PubMedDate not supplied

Computer based pattern recognition of carotid artery Doppler signals for disease classification: prospective validation.

A computer based pattern recognition method has been developed to classify the percent diameter reduction in nonoccluded internal carotid arteries. Using a combined B-mode/pulsed Doppler unit, the system utilizes spectral waveforms obtained from the low common and proximal internal carotid artery locations. The ECG-R wave is used as a time reference to synchronize the averaging of Doppler spectra from 20 heart cycles. An averaged waveform is generated and represents the spectral data from which features are extracted for analysis. A stepwise selection algorithm identifies a feature subset for partitioning the entire range of disease into two states, less than and greater than a decision point. Three such partitions are made, leading to the following categories: Normal, 1-20, 21-50 and 51-99% dia. reduction. A classifier was trained, tested prospectively against unknown data and the results compared to angiography. Of the 170 vessels tested, 141 (82%) were classified in the same category by angiography and the computer system. Agreement for each category was 93% (27/29) for the normals, 81.5% (44/54) for the 1-20% lesions, 78% (29/37) for the 21-50% lesions and 82% (41/50) for the 51-99% lesions. The computer method and angiography differed by more than one category in only one of the 170 tests. The level of agreement corrected for chance (Kappa +/- SE(K] was 0.769 +/- 0.039. Future efforts will be directed toward dividing classification of disease further (especially in the 51-99% category), developing a dedicated microprocessor for on-line analysis of the signals and using the system for prospective epidemiological studies of various populations.

Adult↗
PubMedDate not supplied

Hemodynamics of the normal human carotid bifurcation: in vitro and in vivo studies.

The spatial and temporal characteristics of blood flow in the normal adult human carotid bifurcation are investigated by two different methods: in vitro pulsatile flow model experiments using laser Doppler anemometry and in vivo studies employing pulsed Doppler velocity measurements obtained with an ultrasound duplex scanner. Glass and Plexiglas models based upon arteriographic measurements were evaluated with laser Doppler anemometer methods for pulsatile flow. A similarity approach permits the model study to be geometrically and hydrodynamically accurate with respect to the human carotid bifurcation. These parallel but separate approaches were originally performed by the principal authors without knowledge of each others' work. Normal flow patterns in the proximal internal carotid artery are demonstrated to include: unidirectional, helical, transient reversal, and low velocity regions of flows. The characterization of these complex temporal and spatially variant flow fields required the high sample volume resolution afforded by the model study. Pulsed Doppler ultrasound and a novel method of positioning the sample volume permitted a qualitative description of the complex flow velocity fields in the normal human bifurcation. Results of the two methods are compared and a striking similarity between the two methods is observed for the primary and secondary flow features. The problem of associating blood flow velocity disturbances with the presence of intralumenal disease is addressed in the discussion. It is suggested that the flow disturbances associated with the normal carotid bifurcation are different from those associated with intraluminal disease and further, that the secondary flow structures can be usefully employed to establish normalcy.

Adult↗
PubMedDate not supplied

Sources of variability in carotid duplex examination: a prospective study.

Interobserver and intraobserver variability of ultrasonic, duplex carotid artery examinations was studied in a prospective, randomized, and blinded clinical trial. Forty-eight patients were examined by two technologists, yielding 96 carotid artery examinations. The kappa statistic was calculated to determine the degree of agreement corrected for chance. The kappa value between examinations by different technologists was 0.476. Variability occurred at both steps in the examination procedure: (1) obtaining the velocity waveforms (kappa = 0.536); and (2) using these waveforms to classify the extent of carotid disease (kappa = 0.609 for interobserver variability in reading waveforms). Minimal to moderate disease categories accounted for most of the variability. There was little disagreement in categorizing lesions as greater than or less than 50% diameter reduction. Intraobserver variability in rereading spectral waveforms was minimal (kappa = 0.842 and 0.894). Recognition of disturbed flow patterns in normal carotid bulbs may reduce variability.

Carotid Artery Diseases↗
PubMedDate not supplied

Noninvasive mapping of lower limb arterial lesions.

Thirty patients with peripheral arterial disease were evaluated using an ultrasonic duplex scanner. A total of 338 arterial segments from the level of the iliac to the popliteal artery were studied and compared with the results of arteriography read independently by two radiologists who were unaware of the results with the scanner. The results demonstrate that this method is not only suitable for clinical use but is as good as arteriography in defining both the location and extent of the arterial involvement.

Adult↗
PubMedDate not supplied

Pseudocolor displays in B-mode imaging applied to echocardiography and vascular imaging: an update.

Cardiac and vascular ultrasound systems incorporting colorized gray-scale display options to supplement the standard B-mode gray-scale image have recently reappeared on the market from several manufacturers. As yet, the clinical benefit of this "new" technology is unknown, and recommendations and protocols for its best application are not available. This article reviews the limitations of the gray-scale displays currently used, the rationale of the color-supplemented B-mode image, and some of the potential applications to cardiac and vascular ultrasound.

Color↗
PubMedDate not supplied

Prevalence of severe arteriosclerosis obliterans in patients with diabetes mellitus. Relation to smoking and form of therapy.

Noninvasive methods were used to determine the prevalence and severity of arteriosclerosis obliterans associated with diabetes in 674 subjects including 153 recruited as controls. A resting ankle systolic blood pressure that was less than 90% of the arm pressure indicated severe arteriosclerosis obliterans. Of the 71 subjects with severe disease, 64 (90%) had a history of smoking, which is significantly greater than the 60% overall smoking rate (p less than 0.001). In non-insulin-dependent diabetic smokers, the diet-treated subjects had 2.5 times the prevalence of severe arteriosclerosis obliterans as those treated with insulin (p = 0.01); the sulfonylurea-treated subjects had twice the prevalence of severe disease as those treated with insulin (p = 0.015).

Adult↗
PubMedDate not supplied

Prospective study of atherosclerotic disease progression in the renal artery.

BACKGROUND: The aim of this study was to determine the incidence of and the risk factors associated with progression of renal artery disease in individuals with atherosclerotic renal artery stenosis (ARAS). METHODS AND RESULTS: Subjects with >/=1 ARAS were monitored with serial renal artery duplex scans. A total of 295 kidneys in 170 patients were monitored for a mean of 33 months. Overall, the cumulative incidence of ARAS progression was 35% at 3 years and 51% at 5 years. The 3-year cumulative incidence of renal artery disease progression stratified by baseline disease classification was 18%, 28%, and 49% for renal arteries initially classified as normal, <60% stenosis, and >/=60% stenosis, respectively (P=0.03, log-rank test). There were only 9 renal artery occlusions during the study, all of which occurred in renal arteries having >/=60% stenosis at the examination before the detection of occlusion. A stepwise Cox proportional hazards model included 4 baseline factors that were significantly associated with the risk of renal artery disease progression during follow-up: systolic blood pressure >/=160 mm Hg (relative risk [RR]=2.1; 95% CI, 1.2 to 3.5), diabetes mellitus (RR=2.0; 95% CI, 1.2 to 3.3), and high-grade (>60% stenosis or occlusion) disease in either the ipsilateral (RR=1.9; 95% CI, 1.2 to 3.0) or contralateral (RR=1.7; 95% CI, 1.0 to 2.8) renal artery. CONCLUSIONS: Although renal artery disease progression is a frequent occurrence, progression to total renal artery occlusion is not. The risk of renal artery disease progression is highest among individuals with preexisting high-grade stenosis in either renal artery, elevated systolic blood pressure, and diabetes mellitus.

Aged↗
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Carotid artery velocity patterns in normal and stenotic vessels.

Duplex scanning provides real time B-mode images of the carotid bifurcation vessels along with a single gate pulsed Doppler flow velocity detector. By using the B-mode output of the duplex system to measure the Doppler angle and spectrum analysis to measure the frequency content of the Doppler signal, instantaneous flow velocity can be calculated. Mean velocity at peak systole was calculated retrospectively in 68 common (CCA) and internal (ICA) carotid arteries of 39 patients who had undergone prior angiography and prospectively in 30 arteries of 15 healthy young controls. The ratio of mean peak ICA velocity to mean peak CCA velocity at systole (VICA/VCCA) was below 0.8 in all 36 normal arteries and above 1.5 in all 21 high-grade stenoses of 60% or greater diameter reduction. Sixty-one percent of 41 vessels with less than 10 to 55% diameter reduction had a velocity ratio between 0.8 and 1.5. Only 10% of all ICA's with any stenotic lesion were incorrectly classified as normal. VICA/VCCA appears to be an accurate indicator of the degree of ICA stenosis.

Adult↗