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At least 289 records · Page 16Linked to original sources

PubMed1995

[Intrarenal color Doppler ultrasound for exclusion of renal artery stenosis in cases of multiple renal arteries. Analysis of the Doppler spectrum and tardus parvus phenomenon].

PURPOSE: To diagnose possible renal artery stenosis especially in case of multiple renal arteries by intrarenal colour-coded Duplex sonography. METHODS: In 50 hypertensive patients lobar and interlobar arteries were looked for at 3 different levels. Analysis included the determination of the early systolic acceleration time and the assessment of the Doppler waveform, especially the "tardus-parvus" phenomenon. Intraarterial angiography was performed in all patients the next day. RESULTS: In 48/50 patients the sonographic investigations were sufficiently evaluable. Angiography showed haemodynamically relevant stenosis in 13 patients, in 4 patients bilaterally. In 21 patients (42%) multiple renal arteries were found. Sensitivity and specificity in the diagnosis of renal artery stenosis was 77% respectively 46% (threshold value > or = 0.120 s). In 10/17 angiographically verified haemodynamically relevant renal artery stenosis a change of the Doppler waveform was noted; sensitivity in the diagnosis of renal artery stenosis was 69%, specificity 90%. CONCLUSION: Intrarenal colour-coded Duplex sonography cannot be recommended as a screening tool for renal artery stenosis.

Adult↗

PubMed1992

Doppler and color Doppler imaging in acute transplant failure.

Most renal transplants are lost by rejection. A method is required to identify and discriminate between this and acute tubular necrosis and cyclosporin toxicity. The sonogram of the normal renal transplant is characteristic. Early Doppler studies measuring a rise in vascular impedance in acute rejection showed a high sensitivity and specificity. This appears, at least in part, to have been due to patient selection. We conclude that Doppler studies cannot be used to differentiate between the main parenchymal causes of renal transplant failure, although it can be helpful, with other clinical information, in supporting a diagnosis and in monitoring the effects of treatment.

Acute Kidney Injury↗

PubMed1990

Major pitfalls in Doppler investigations. Part II. Low flow velocities and colour Doppler applications.

Many pitfalls result from the limited ability of Doppler instruments to record low flow velocities. These include a misleading resistance or pulsatility index due to diastolic cut-off and taking no signal to equal no flow assuming that no signal means no flow. Comparison of actual flow velocities as measured in an in-vitro system (range: 0.8 to 3.4 cm/s) with the lowest recordable spectral or colour signals in 3 Duplexscanners showed that reduced sensitivity to low flow velocities is not only dependent on the high pass ("wall") filter setting, Doppler frequency or angle of incidence, but also on factors such as vessel diameter, impairing the signal to noise ratio. Characteristic errors of colour flow mapping (misleading vascular anatomy, imitation of pathological findings, erroneous exclusion of flow) are due to partial volume effect, limited temporal and velocity resolution, changing angle of incidence, aliasing and failure to detect low flow velocities.

Adult↗

PubMed1987

Noninvasive evaluation of mid-left ventricular obstruction by two-dimensional and Doppler echocardiography and color flow Doppler echocardiography.

Three patients with midventricular obstruction resulting from three different pathophysiologic mechanisms and differing anatomic bases for the development of obstruction are presented. In the first patient, a membrane-like structure appeared to cause some fixed obstruction, but a superimposed dynamic component to the obstruction was also evident. Papillary muscle hypertrophy with approximation of the papillary muscles during systole was the mechanism in the second patient. In the third patient, apical infarction with hyperdynamic contraction of the mid- and basal portions of the myocardium appeared to be the pathophysiologic mechanism. Color flow Doppler echocardiography was particularly useful in localizing the site of obstruction and allowed further evaluations by pulsed and continuous-wave Doppler techniques to precisely determine pressure gradients.

Blood Pressure↗

PubMedDate not supplied

Doppler spectral characterization of flow disturbances in the carotid with the Doppler probe at right angles to the vessel axis.

This paper reports on a new method intended to detect early flow disturbances generated by small lesions, using conventional clinical instrumentation. In vitro experiments on models of stenotic vessels are presented which prove that ultrasound Doppler, with the beam directed at right angles to the vessel axis can detect vortices and other flow disturbances caused by wall irregularities. These disturbances characterized by small velocity components first toward and then away from the transducer correlate with the spectrum of vortices caused by small artificial lesions. We found these disturbances in flow to be too small to cause detectable broadening in the Doppler spectrum acquired in the traditional way (i.e. with the beam at an angle less than 90 degrees). The detected flow disturbances were found to depend on the surface roughness, the profile of the obstructive lesion and the narrowing of the vessel. Similar flow disturbances to those detected in vitro were demonstrated in vivo for this new beam orientation in regions of the carotid, such as the bulb and the beginning of the common carotid, where vortex-like flows are expected.

Adult↗

PubMed1988

High Doppler-derived cardiac output in the cerebral arteriovenous fistula measured by pulsed Doppler ultrasound.

Cerebral arteriovenous fistula may cause a significant increase in cardiac output. So far, the right ventricular output measurement with conventional cardiac output methods has been difficult in newborn infants because of the shunts through the foramen ovale and patent ductus arteriosus. This difficulty can be avoided by measuring left ventricular output with the pulsed Doppler ultrasound method. In our case, the patient was a newborn infant with large patent ductus arteriosus and an arteriovenous malformation of the great cerebral vein of Galen. The malformation was found by noticing a loud murmur from the infant's head. The diagnosis was later confirmed by ultrasound scanning and a computer tomography. Left ventricular output was enormous with values from 740 to 830 ml/min/kg, when the normal value for the newborn infant at this age is 260 ml/min/kg. Because of constant cardiac failure, the malformation was operated on. The infant died of cardiac failure during this operation. An enormous left ventricle output in an infant with arteriovenous fistula and patent ductus arteriosus predisposes to cardiac failure. The Doppler ultrasound method in newborn infants seems to be a useful tool to determine cardiac function.

Blood Flow Velocity↗

PubMed1990

[Imaging of penile vascular anastomoses using color-coded Doppler ultrasound: comparison with CW Doppler ultrasound and clinical aspects].

In fourteen patients undergoing surgical revascularization (11 with Hauri's, three with Virag's anastomosis) because of erectile dysfunction, the patency of vascular anastomosis was evaluated and visualized by color-coded-Doppler sonography (CCDS). Results were compared with continuous-wave Doppler (CWD) and clinical data. CCDS proved to be superior to CWD with regard to assessment of flow in the penile vessels and to applicability. Strength and direction of flow can be judged visually. Therefore, the nature of the imaged vessel (artery or vein, deep or dorsal artery) can be differentiated. There is a good correlation of CCDS and CWD in their evaluation of the patency of the anastomosis. CCDS showed higher accuracy in detecting deep cavernosal arteries.

Adult↗

PubMed1983

[Ultrasonic Doppler sonography in ophthalmological practice (the Doppler retina)].

This paper presents the case histories of two patients with embolism of the central retinal artery. Non-characteristic headache (lasting longer in one patient than in the other) preceded acute vascular obliteration. In the first case the headache symptom occurred simultaneously with organic findings of stenosis of the carotid artery. The author describes the findings obtained with modified Doppler sonography ("central artery Doppler"). "Retinal hemotachygrams" are analyzed.

Aged↗

PubMed2003

Doppler effect in resonant photoemission from SF6: correlation between Doppler profile and Auger emission anisotropy.

Fragmentation of the SF6 molecule upon F 1s excitation has been studied by resonant photoemission. The F atomiclike Auger line exhibits the characteristic Doppler profile that depends on the direction of the photoelectron momentum relative to the polarization vector of the radiation as well as on the photon energy. The measured Doppler profiles are analyzed by the model simulation that takes account of the anisotropy of the Auger emission in the molecular frame. The Auger anisotropy extracted from the data decreases with an increase in the F-SF5 internuclear distance.

Journal Article↗

PubMed1990

Does pulsed-Doppler ultrasound have mutagenic effects? Application of the Ames mutagenicity assay to test pulsed-Doppler equipment.

Measurement of fetal blood flow has been accepted using pulsed-Doppler ultrasound. Until recently, there has been a lack of investigations concerning the potential risks of this method. The possible mutagenic effect of a pulsed-Doppler system was examined in vitro by applying the Ames test. Tester strains of Salmonella typhimurium indicating point mutations were irradiated (TA 98, TA 100, TA 102, TA 1535, TA 1537, TA 1538). A commercially available duplex system was applied in the experiments emitting an ultrasound beam with a spatial-peak temporal-average of 5.2 mW/cm2 and a spatial-peak temporal-peak of 117 mW/cm2 at a frequency of 2 MHz. The tester strains were sonicated up to 60 minutes, the bacterial suspension being in direct contact with the transducer surface. The ultrasound-exposed bacterial suspensions were compared with nonexposed samples. Reference mutagens were used for checking the sensitivity of the system. The results do not indicate any mutagenic effects.

DNA Damage↗

PubMed1999

Noninvasive Measurement of Left Coronary Blood Flow Reserve by Transthoracic Doppler Echocardiography: Comparison with Doppler Guidewire Ultrasonography.

The development of new ultrasound instrumentation has made epicardial coronary artery blood flow imaging easier with the use of transthoracic coronary Doppler echocardiography (TCDE). This study was performed to investigate the accuracy of coronary blood flow reserve (CFR) measurement by TCDE. In 15 patients with ischemic heart disease in the absence of valvular disease or atrial fibrillation, coronary flow at rest and flow with hyperemia induced by intravenous dipyridamole infusion were recorded by TCDE and Doppler guidewire ultrasonography. The CFR was determined as the ratio of the maximum hyperemic diastolic time-averaged peak velocity to the velocity at rest in the proximal or distal left anterior descending coronary artery. It was found that the CFR of the left anterior descending coronary artery measured by TCDE was comparable in accuracy with CFR measured by invasive methods (r = 0.87, P < 0.0001, n = 15).

Journal Article↗

PubMedDate not supplied

Cerebrovascular evaluation: assessment of Doppler scanning of carotid arteries, ophthalmic Doppler flow and cervical bruits.

In 38 patients who underwent cerebrovascular evaluation followed by angiography the Doppler ultrasound scanning technique was found to be an excellent screening procedure for detecting marked stenosis (greater than 50%) or occlusion of the internal carotid artery (93% correlation). It is noninvasive, easily reproducible and can be performed by a qualified technician. The major problems are: the inability to detect ulcerated plaques without marked stenosis, the requirement for patient cooperation (lying still for periods of 15 minutes), and the fact that it assesses only the extracranial circulation. Screening with just the directional ophthalmic Doppler flow signal yielded a high percentage of false negatives (13%). The presence of a cervical bruit may indicate an underlying stenosis of the internal carotid artery, but may also be due to stenosis of the external carotid artery or other factors such as increased blood flow, vessel tortuosity, etc. (12% false positives). Absence of a cervical bruit does not exclude internal carotid artery disease (ulcerated nonstenotic plaque or occlusion).

Arterial Occlusive Diseases↗

PubMed1992

Closure of the ductus venosus in neonates: findings on real-time gray-scale, color-flow Doppler, and duplex Doppler sonography.

OBJECTIVE: Our objective was to document the anatomy, flow pattern, and time of closure of the ductus venosus in healthy full-term neonates. SUBJECTS AND METHODS: We examined the ductus venosus in 73 neonates by using gray-scale sonography, color flow imaging, and duplex Doppler sonography. Each neonate was examined 1-2 days after birth, 6-7 days after birth, and then every 3-4 days until closure was confirmed or the neonate was 18 days old. The length, width, and color flow and duplex Doppler characteristics of the ductus were noted. Closure of the ductus at 6-7 days after birth was examined with respect to birth weight, hemoglobin level, and gestational age. RESULTS: The ductus venosus, extending from the left portal vein to the inferior vena cava, was identified with all three techniques. The ductus was patent in all 73 neonates 1-2 days after birth. It was still patent in 41 (68%) of 60 neonates reexamined 6-7 days after birth and in two of three neonates (11% [7/60]) reexamined 17-18 days after birth. Blood flow within the ductus was cephalic, in a constant venous waveform. Initial flow velocity ranged from 0.15 to 0.70 m/sec and decreased consistently in subsequent examinations. There was no significant difference in birth weight, hemoglobin level, or gestational age between the group whose ductus was closed and the group whose ductus was open at 6-7 days after birth. CONCLUSION: The ductus venosus in neonates is consistently detectable on sonography. It is patent in a greater percentage of neonates, and for a longer time, than was previously shown with conventional radiographic studies with angiography.

Blood Flow Velocity↗

PubMed1996

[Contrast medium supported imaging of tumorous vessels by color Doppler and power Doppler mode in animal experiments].

PURPOSE: The purpose was to determine tumor neovascularisation via colour-coded Doppler (duplex) sonography and the "power mode", both visually and quantitatively, by means of videodensitometry. MATERIAL AND METHODS: 6 VX2 tumours of 4 to 11 mm size were implanted in 4 rabbits at various sites. The colour-coded duplex sonography and the new sonographic power technique were tested before and after having injected a new contrast medium (SH U 616A). RESULTS: If no contrast medium was injected, tumour neovascularisation was identified in only 50% of the cases. Injection of contrast medium increased signal intensity three to fourfold with all examined tumors. Combined use of the sonographic method by the power technique with injection of contrast medium is outstandingly suitable for tumor vessel imaging even of small tumors, as these initial results seem to show. CONCLUSION: If these results are corroborated by further studies, contrast-medium supported sonographic technique may possibly become established as an alternative method to other imaging procedures.

Adipose Tissue↗

PubMed1999

Neonatal cerebral Doppler: arterial and venous flow velocity measurements using color and pulsed Doppler system.

OBJECTIVE: To contribute to the establishment of reference values of blood flow velocity assessed by cerebral Doppler in healthy infants related to gestational age and birth weight during the first week of life. METHODS: Five arteries and three veins were evaluated respectively in 120 (74 premature) newborns and in 100 (70 preterm) infants. In a quarter of the latter three recordings at 5-minute intervals were made to assess reproducibility. The relation between flow measurements and gestational age was assessed by linear regression, means by analysis of variance (or Kruskall-Wallis test) and paired samples by Student's t test. RESULTS: There was a significant increase of arterial velocities with increasing gestational age and birth weight, but not for venous velocities. Significant higher values were found in the internal carotid artery followed by the medium cerebral artery. The venous velocities were highly reproducible and the main patterns observed were bandlike and sinusoid type. CONCLUSION: The knowledge of normal cerebrovascular physiology is essential to understand the pathogenesis of neonatal brain damage and can help pediatricians in an accurate interpretation of the flow profile in neurological pathology.

Arteries↗

PubMed1994

[Comparison of the results of conventional ultrasonography and color doppler analysis in the evaluation of the nature of adnexal tumors. II. Color duplex doppler ultrasonography].

The author evaluates the possibilities of coloured Doppler vaginosonography for prebioptic evaluation of the nature of ovarian tumours. He investigated the site of vascularization of tumours and qualitatively the blood flow by assessing the vascular resistance (PI, RI) and character of the flow velocity curve. The results revealed a statistically significant (p < or = 0.05) trend of central vascularization of malignant tumours. A new parameter with a 100% sensitivity and 89% specificity proved to be the notch at the beginning of the diastolic part of the velocity curve which was not observed in any carcinomas but was present in 89% of benign lesions. The vascular resistance was significantly lower in malignant tumours. The cut off value of malignity of the pulsatility index PI = 0.7 had a 86% sensitivity and 100% specificity. The cut off value of the resistance index RI is 0.6 with a 100% sensitivity and 75% specificity. Comparison of the predictive values of malignity of conventional and coloured duplex ultrasonography revealed that for evaluation of the nature of ovarian tumours coloured duplex sonography with several parameters is more suitable. PI and RI alone can be considered rather as indicators of active growth.

Adult↗

PubMed1998

Endothoracic sonography with color Doppler availability during video assisted thoracic surgery (videothoracoscopic operative staging with ultrasound color Doppler) for lung cancer staging.

BACKGROUND: The preoperative staging of lung cancer can be problematical when we attempt to evaluate T factor (T2-T3 versus T4) and N factor (N0 versus N1-N2). In some cases, radiology tests (CT scan, magnetic resonance imaging) cannot entirely dispel the possibility that the mediastinal structures have been infiltrated. N factor is evaluated mainly by dimensional criteria. However, mediastinoscopy and mediastinotomy do not allow the full exploration of all mediastinal mode stations. METHOD: Starting in 1995, we submitted 10 consecutive patients to videothoracoscopic operative staging with ultrasound color Doppler (VOS-USCD). In five cases, preoperative staging showed possible infiltration of the pulmonary artery (T4). In nine cases, we found involvement of the mediastinal nodes, seven patients were N2, and two were N3. Videothoracoscopy was performed under general anesthesia using a double-lumen endotracheal tube. The videothoracoscope and sonographic probe were inserted via three thoracoports placed in the axillary triangle. RESULTS: Following the results of VOS-USCD, the staging and subsequently the therapeutic program were modified in seven of 10 cases (70%). CONCLUSIONS: Our preliminary experience indicates that VOS-USCD should be applied to the diagnosis of patients in stage IIIA (N2) and that it is particularly valuable for patients in stage IIIB.

Aged↗

PubMed2006

Real-time three-dimensional color Doppler echocardiography overcomes the inaccuracies of spectral Doppler for stroke volume calculation.

Real-time 3-dimensional echocardiography is increasingly used in clinical cardiology. Studies have been shown that this technique can be accurately used to assess both cardiac mass and chamber volumes. We review the work showing that real-time 3-dimensional Doppler echocardiography can be used to accurately calculate intracardiac flow volumes that can potentially be used to assess cardiac function, intracardiac shunt, and valve regurgitation.

Computer Systems↗