Angle Of Insonation Research Articles

Angle dependence and transit time effect in Doppler flow measurement

Objective: In clinical practice, obvious differences exist between the Doppler theory which does not allow a frequency shift at right angles of insonation, and the fact that a frequency is generated. Possible technical and physical causes were evaluated in our study. Methods: A laminar, non-pulsatile flow model was insonated between 35° and 155° with pulsed wave (pw) Doppler sonography incorporated in a duplex scanner. Results: For all angles tested the maximum frequencies were higher than predicted by the Doppler formula. The frequency shift observed at perpendicular insonation cannot be explained by the Doppler theory. Conclusions: The results obtained can be explained by intrinsic spectral broadening (ISB) caused by the transit time effect or equivalently by the geometry of the ultrasonic beam. These effects have to be considered when the maximum frequency is employed to quantify flow volume or when spectral broadening is used as an indicator of disturbed flow.

Angle dependence and transit time effect in Doppler flow measurement

Objective: In clinical practice, obvious differences exist between the Doppler theory which does not allow a frequency shift at right angles of insonation, and the fact that a frequency is generated. Possible technical and physical causes were evaluated in our study. Methods: A laminar, non-pulsatile flow model was insonated between 35° and 155° with pulsed wave (pw) Doppler sonography incorporated in a duplex scanner. Results: For all angles tested the maximum frequencies were higher than predicted by the Doppler formula. The frequency shift observed at perpendicular insonation cannot be explained by the Doppler theory. Conclusions: The results obtained can be explained by intrinsic spectral broadening (ISB) caused by the transit time effect or equivalently by the geometry of the ultrasonic beam. These effects have to be considered when the maximum frequency is employed to quantify flow volume or when spectral broadening is used as an indicator of disturbed flow.

Measurement of volumetric flow with no angle correction using multiplanar pulsed Doppler ultrasound.

In this paper we show that by scanning at points on the surface of a sphere that the normal angle correction used in pulsed Doppler flow measurements is no longer necessary. Thus, it is possible to measure three-dimensional (3-D) flow using multiplanar ultrasound even though we only get one-dimensional (1-D) velocity information from pulsed Doppler ultrasound. The technique handles the three basic problems in flow measurements using ultrasound Doppler: The variations of the cross-sectional area, the time dependent changes in the velocity field, and the dependency of the angle of insonation. The technique is tested in a flow phantom using different angles of insonation to validate the angle independence of this new technique. Using six different angles of insonation in the range 0 degree to 69 degrees with flowrates in the range of 0-170 ml/s a linear dependence was found to be: measured (color Doppler) = 0.98 real flow (reference) + 1.36 ml/s, with a 95% confidence interval of +/- 13.9 ml/s.

Effect of the insonification angle on the Doppler backscattered power under red blood cell aggregation conditions

It has been reported that power color Doppler ultrasound has important advantages over conventional color Doppler flow imaging. Some of these advantages are the aliasing free capability, the increased sensitivity to flow, and the angular independence. This last characteristic of power Doppler ultrasound was evaluated to verify if it was still valid in some well-defined flow conditions where porcine whole blood, calf red cells suspended in saline solution, and carbon fibers suspended in a water-glycerol mixture were used as scattering particles. Experiments were conducted under steady flow conditions (mean shear rates across the tube between 8.5 and 102 s/sup -1/) for insonification angles between 40 and 80/spl deg/. Different hematocrit values (5, 10, 20, and 40%) were specifically tested for porcine whole blood. Results indicated no angular dependence for the saline suspension of calf red cells while a strong anisotropy was observed for the carbon fibers. In this last situation, the Doppler power in decibels increased linearly with the insonification angle. The maximum found at 800 suggests that the fibers were aligned with the direction of the flow. For porcine whole blood, an angular dependence was observed at some specific shear rate conditions. At 40% hematocrit, the anisotropy was about 5 dB for shear rates between 17 and 51 s/sup -1/, while for a lower (8.5 s/sup -1/) or higher shear rate (102 s/sup -1/), the anisotropy was reduced to approximately 2 dB. In all of these situations, the maximum Doppler power was observed for an insonification angle between 45 and 60/spl deg/, For hematocrit values of 5, 10, and 20%, the anisotropy was respectively on the order of 2, 3, and 4 dB or less, depending on the shear rate conditions. Among the possible mechanisms that may explain the anisotropic effect observed in the present study, the structure of the red cell aggregates is believed to be the determinant factor. A hypothesis concerning the structure of the aggregates under flowing conditions in large diameter tubes is proposed.

Development of quantitative Doppler indices for uteroplacental and fetal blood flow during the third trimester

The aim of our study was to describe the development of uteroplacental and fetal blood flow during the third trimester. Doppler examination was carried out on 393 uncomplicated pregnancies with uncomplicated term delivery. Using a pulsed color Doppler, we calculated the maximum systolic, mean and maximum end-diastolic velocity after correcting the angle of insonation. Patients under tocolysis or other medication influencing blood flow parameters were excluded from this cross-sectional study. Summarizing the results gained by Doppler ultrasound investigation of the uteroplacental and fetal blood vessels, we created quantiles as quantitative Doppler indices for the maximum systolic, mean (TAMX = time averaged maximum velocity) and maximum end-diastolic velocity. The following conclusions could be drawn: (1) resistance to the blood flow in the maternal portion of the placenta does not change during the third trimester; (2) resistance to the blood flow on the fetal side of the placenta decreases up to week 42 of gestation; (3) cerebral vascular resistance decreases constantly up to gestational week 42; and (4) vascular resistance to the blood flow of the kidney decreases only slightly during the third trimester. This study offers clinically important values for quantitative Doppler flow velocimetry for the first time. We hope that our findings improve the usefulness of Doppler ultrasound as a diagnostic tool in obstetrical management.

Comparative Study of Power-Based Versus Mean Frequency-Based Transcranial Color-Coded Duplex Sonography in Normal Adults

Power-based transcranial color-coded duplex sonography (p-TCCD) is a new ultrasonic method that has advantages compared with frequency-based TCCD (f-TCCD), since it is essentially independent of the angle of insonation, not subject to aliasing, and has a better signal-to-noise ratio. The purpose of this study was to evaluate the ability of p-TCCD to visualize flow in cerebral parenchyma and to compare the advantages, limitations, and reliability of velocity measurements of p-TCCD versus f-TCCD in the major basal cerebral arteries of normal subjects. Two investigators performed 15 p-TCCD and 15 f-TCCD studies in 30 normal subjects with adequate ultrasonic windows. Each investigator did a p-TCCD or f-TCCD study in every patient, and each was blinded in every case to the results of the other. Peak systolic (Vs) and end-diastolic (Vd) velocities were determined in the anterior, middle, and posterior cerebral, basilar, and vertebral arteries. The reliability of p-TCCD velocimetry was evaluated by calculating both the correlation coefficient (r) of the difference between p-TCCD versus f-TCCD measurements and the coefficient of variation (CV), defined as the difference between the mean values for p-TCCD and f-TCCD divided by the mean values for f-TCCD measurements, expressed as percent. p-TCCD did not display flow in cerebral parenchyma but depicted arteries with a course perpendicular to that of the ultrasound beam and showed good reliability of velocity measurements in all examined arteries: for Vs, r was .84 to .93 (P < .001) and CV was 7.7% to 10.8%; for Vd, r was .87 to .90 (P < .001) and CV was 10.3% to 13.7%. The lack of directional and velocity information and tissue motion artifacts were unimportant limitations in p-TCCD. Compared with f-TCCD, p-TCCD had no important advantages but had several unimportant limitations in a study of normal adults with adequate ultrasonic windows.

Transcranial color-coded duplex sonography in cerebral arteriovenous malformations.

It is well known that significant changes in cerebral hemodynamics may occur during the treatment of cerebral arteriovenous malformations with the complication of intracerebral hemorrhage and parenchymal edema. We used transcranial color-coded duplex sonography to study alterations in blood flow velocities during staged embolization. Forty-one patients aged 40 +/- 13 years (mean +/- SD) with angiographically proven cerebral arteriovenous malformations were studied. The blood flow velocities of the anterior, middle, and posterior cerebral arteries were measured in 16 patients with supratentorial arteriovenous malformations, both before the first and then after each successive embolization (three to seven treatments). In 29 of 41 patients (71%), transcranial color-coded duplex sonography satisfactorily revealed the malformations and their main feeders. After the final embolization, we found a reduction in the peak flow velocity in treated feeders of 23 +/- 28% compared with the values before the first embolization. The untreated feeders showed an increase in peak flow velocities of 12 +/- 23% as an expression of increased collateral flow. After the treatment of the supplying feeders, we observed a reduction in flow velocity of 25 +/- 13% in seven patients, with cross-filling of the arteriovenous malformation through the contralateral anterior cerebral artery and the anterior communicating artery. The technical advantage of transcranial color-coded duplex sonography compared with transcranial Doppler sonography is that it allows the exact identification of different feeding arteries in arteriovenous malformations. Repeated measurements during stepwise embolization with corrected insonation angle are easily achieved, and noninvasive quantification of hemodynamic changes is possible. The method may be helpful in the planning of the different steps of embolization.

Beat-by-beat forearm blood flow with Doppler ultrasound and strain-gauge plethysmography

Simultaneous Doppler ultrasound estimates of brachial artery mean blood velocity (MBV) and venous occlusion strain-gauge plethysmography measures of forearm blood flow (FBF) were performed to determine the beat-by-beat relationship between the two methods and provide a method for flow calibration of Doppler MBV estimates. Such a calibration of Doppler MBV eliminates the need for knowledge of vessel cross-sectional area and angle of insonation while allowing for the quantification of limb blood flow. Six healthy subjects (5 men and 1 woman) performed 40 s of isometric forearm contraction at 35% maximal voluntary contraction with arterial inflow occluded. This resulted in elevated blood flow on relaxation and cuff deflation, and simultaneous beat-by-beat Doppler MBV and strain-gauge FBF measurements were then made over a period of 2-3 min as flow gradually decreased to resting levels. The r2 values for the fitted regression lines over a wide range of flows ranged from 0.87 to 0.98, and the mean square error terms ranged from 0.88 to 3.07 ml.100 ml-1.min-1. Significant day-to-day variation of the fitted regression parameters within subjects indicated that quantitative estimates of FBF from Doppler MBV require a calibration to be performed for each experiment. The finding of a strong linear relationship between Doppler MBV and venous occlusion strain-gauge plethysmography, as well as the marked beat-by-beat effect of cuff inflation on blood flow, confirms the importance of calibration on the same beats, not on adjacent segments of beats.

Doppler spectrum shape analysis based on the summation of flow-line spectra

A method of evaluating the shape of the Doppler spectrum in pulsed wave (PW) Doppler flowmeters in the presence of velocity gradients is presented and is demonstrated for a circular geometry transducer insonating a uniform distribution of isotropic scatterers moving in paraxial conditions. The method computes the spectrum shape by adding the power spectra of individual flow lines present in the sample volume of the moving fluid being analyzed and can be applied to any focused transducer aperture for which the flow-line spectra are known. With a parabolic velocity profile insonated by a focused circular transducer, several computed spectra are compared with experimental ones for different insonation angles; it is also shown how changes in the spectral shape, due to variations of sample volume size, can be evaluated. The results should help to provide a better understanding of PW Doppler spectrum broadening and its use in medical ultrasound diagnostics.

Experimental evaluation of velocity and power estimation for ultrasound blood flow imaging, by means of a two-dimensional autocorrelation approach

This paper evaluates experimentally the performance of a novel axial velocity estimator, the 2D autocorrelator, and its Doppler power estimation counterpart, the 2D zero-lag autocorrelator, in the context of ultrasound color flow mapping. The evaluation also encompasses the well-established 1D autocorrelation technique for velocity estimation and its corresponding power estimator (1D zero-lag autocorrelator), to allow performance comparisons under identical conditions. Clutter-suppressed in vitro data sets from a steady-flow system are used to document the effect of the range gate and ensemble length, noise level and angle of insonation on the precision of the velocity estimates. The same data sets are used to examine issues related to the estimation of the Doppler signal's power. The first-order statistics of power estimates from regions corresponding to flow and noise are determined experimentally and the ability of power-based thresholding to separate flow signals from noise is characterized by means of ROC analysis. In summary, the results of the in vitro evaluation show that the proposed 2D-autocorrelation form of processing is consistently better than the corresponding 1D-autocorrelation techniques, in terms of both velocity and power estimation. Therefore, given their relatively modest implementation requirements, the 2D-autocorrelation algorithms for velocity and power estimation appear to represent a superior, yet realistic, alternative to conventional Doppler processing for color flow mapping.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Intraoperative Transcranial Doppler Monitoring

Professor of Anesthesiology and Neurological Surgery, University of Washington School of Medicine, Department of Anesthesiology, Harborview Medical Center, 325 Ninth Avenue, ZA-14, Seattle, Washington 98104.To the Editor:--Transcranial Doppler ultrasonography allows continuous noninvasive monitoring of cerebral blood flow velocity and represents an important advance in our ability to monitor intra-cranial hemodynamics. [1]There are practical limitations to its routine intraoperative application, one of which is the constancy of the angle of insonation, i.e., the angle between the direction of the probe and the direction of the artery segment being insonated. Many commercial fixation devices are available, all of which are based on a head-band or head-strap design. Although these devices are functional, they preclude use of the monitor in neurosurgical procedures, which is arguably the area where it can be most useful.We wish to report our experiences with a custom-designed attachment system (in collaboration with DWL, Electronics, Sipplingen, Germany) using car inserts and a foam-padded nose rest to anchor the system, leaving the head unencumbered (Figure 1and Figure 2). The side-mounted transducers are equipped with swivel locks to fix the position, and the thumb wheel mounted on the nose rest allows alteration of tension to achieve optimal signals. With the exception of neurosurgical procedures using subtemporal incisions, its deployment causes no interference. We have used this system successfully for intraoperative monitoring in 12 cases with good results.Arthur M. Lam, M.D.; Professor of Anesthesiology and Neurological Surgery; University of Washington School of Medicine; Department of Anesthesiology; Harborview Medical Center; 325 Ninth Avenue, ZA-14; Seattle, Washington 98104.(Accepted for publication March 13, 1995.)

Critical closing pressure in preterm neonates: Towards a comprehensive model of cerebral autoregulation

In preterm neonates, intraventricular haemorrhage is linked to the dysfunction of cerebral autoregulation (AR). We aimed at tracing the critical closing pressure (CCP) in order to quantify AR and to reveal its inner workings. In an observational study, 10 preterm neonates (median, range: ga 28 weeks, 25 to 32 weeks; bw 1070, 685 to 1730 g; age 2d, 1 to 7 d) were continuously Doppler traced (a. carotis interna) for > 10 min. Systemic blood pressure (BP, a. umbilicalis, a. radialis, a. temporalis) was recorded simultaneously (> 1200 cardiac cycles each). Systolic BP was on average 11 mmHg above CCP. There was a striking parallel between both variables, even in cases of sudden spontaneous BP fluctuations > 30% (r = 0.72, 0.41 to 0.99), while systolic cerebral blood flow velocity remained largely unaffected (r = -0.15, -0.75 to 0.53), indicating a properly functioning AR. CCP was 28 mmHg, 14 to 38 mmHg. Based on our data, a physiological model of AR is developed, integrating anatomy, metabolic and neuronal pathways with former physiologic findings--including low frequency cycling of cerebral blood flow velocity. Tracing of CCP is thought to have the potential to identify infants with impaired AR. Since this method is noninvasive and independent of angle of insonation (thus rendering it uncritical in probe fixation), it is a promising tool for sustained monitoring of cerebral haemadynamics in the clinical setting.

An in vivo model for studying the local haemodynamics of end-to-side anastomoses

To develop an in-vivo model to study the anastomotic flow patterns. Prospective, open, animal study. Polyurethane grafts with an internal diameter equal to the abdominal aorta (8 mm) of 90 kg pigs were implanted as bypass grafts from the supra-renal to the infra-renal level. A novel technique for constructing anastomoses with different anastomosis angles and only slight dilatation was used. The proximal outflow segment was occluded and the flow rate through the graft controlled by clamping the iliac arteries. Visualisation of the flow-fields at the distal end-to-side anastomosis was achieved by a comprehensive colour Doppler mapping protocol. The angulation of the anastomoses was controllable and reproducible. Gross haemodynamic parameters were stable within physiological ranges and were typical for peripheral bypass grafts. The flow fields at the distal end-to-side anastomosis were visualised and found to be in accordance with those reported by in vitro studies. Using different angles of Doppler insonation the same flow field characteristics were found. The model is an appropriate tool for studies of the effects of anastomotic geometry on local flow fields in vivo.

Measurement of blood flow velocity in the basal cerebral circulation: Advantages of transcranial color‐coded sonography over conventional transcranial doppler

Unlike conventional transcranial Doppler (TCD), transcranial color-coded sonography (TCCS) enables imaging of the basal cerebral arteries using color-flow ultrasonography and correction for the angle of insonation when determining blood flow velocities. We present hemodynamic data from 20 normal subjects, each studied with TCD and TCCS. Velocities derived using TCCS with angle correction were significantly greater than those derived using TCD in all vessels (mean velocities [cm/sec; mean with 95% confidence intervals)--anterior cerebral artery: TCD 48 (45-50), TCCS 62 (58-66), p < .0001; middle cerebral artery: TCD 61 (58-64), TCCS 70 (66-74), p < .0001; posterior cerebral artery: TCD 43 (41-46), TCCS 54 (50-57), p < .0001; basilar artery: TCD 40 (34-45), TCCS 45 (38-52), p < .01. Pulsatility index values were significantly greater in all arteries when determined by TCCS, and resistance index values were significantly greater except in the basilar artery. Correcting for the angle of insonation using TCCS may enable estimation of blood flow velocities closer to the "true" values than those derived using conventional TCD.

Quantification of atherosclerotic plaques in carotid arteries by three-dimensional ultrasound

The aim of this study was to develop three-dimensional (3D) ultrasound imaging of the carotid arteries in order to reduce intraexaminer and interexaminer variabilities of volume measurements in follow-up scans of atherosclerotic plaques. The non-invasive quantification of human atherosclerosis by 3D ultrasound was performed using a three-dimensional computer based image reconstruction. The linear movements of the transducer were driven by a motor triggered by electrocardiography. The method included an option to change angle of insonation and a correction of skin contact adaptation. Repeated measurements were performed at weekly intervals in 70 patients. Variabilities and ranges of three newly developed evaluation procedures of plaque volumes (manual tracing, threshold procedure, watershed algorithm) were used. Intraexaminer variability varied between 2.8% (watershed algorithm) and 4.1% (threshold procedure). Interexaminer variability ranged from 4.2% (manual tracing) to 7.6% (threshold procedure), follow-up measurements from 5.2% (watershed algorithm) to 9.4% (threshold procedure). Pearson correlation coefficients of interexaminer agreement and also those between all three measurement procedures were highly significant (p < 0.01). We conclude that the newly developed 3D computer based image reconstruction allows repeated quantification of moderate atherosclerosis with a high reliability.

Quantitative Measurements of Blood Flow Velocity in Basal Cerebral Arteries with Transcranial Duplex Color‐Flow Imaging: A Comparative Study with Conventional Transcranial Doppler Sonography

Transcranial duplex color-flow imaging is a new diagnostic method that allows visual display of blood flow in the basal cerebral arteries. This method allows determination of and correction for the Doppler angle of insonation. Conventional transcranial Doppler sonography has no imaging component and assumes a 0-degree Doppler angle for the calculation of flow velocities. The magnitude of the angle of insonation and the effect on flow velocity estimates have not been clearly defined. In order to evaluate the angle of insonation and the effect of angle correction on velocity readings, 50 patients referred for evaluation of cerebrovascular disease were studied. The mean age was 45 years (range, 24-62 yr). All were examined with conventional transcranial Doppler and transcranial duplex color-flow imaging. Specific vessels of the circle of Willis were identified by location, course, and direction of flow on color-flow images and by depth, direction of flow, and transducer orientation with conventional Doppler sonography. Visually controlled measurements of the Doppler angle of insonation were made by color-flow imaging. The data show that the mean angle of insonation was 33 degrees (+/- 15) in the middle cerebral artery, 35 degrees (+/- 17) in the anterior cerebral artery, 45 degrees (+/- 18) in the posterior cerebral artery, and 15 degrees (+/- 14) in the basilar artery. Angle-corrected peak systolic flow velocities were higher in all vessel segments (middle cerebral = 15%, anterior cerebral = 18%, posterior cerebral = 30%, and basilar = 3%), compared to uncorrected velocity readings by conventional Doppler sonography.(ABSTRACT TRUNCATED AT 250 WORDS)

Transcranial color-coded sonography of the basal cerebral circulation. Reference data from 115 volunteers.

Transcranial color-coded sonography is a new development in noninvasive cerebral vascular imaging. Reference data using this technique are described. Blood velocities and pulsatility and resistance indices were determined in the anterior cerebral, middle cerebral, posterior cerebral, vertebral, and basilar arteries in 115 volunteers after correction for the angle of insonation. Of 1265 basal arterial segments, 1053 were insonated (83%). The vertebral (98%), basilar (92%), middle cerebral (84%), and posterior (P1) cerebral arteries (84%) were the most successfully insonated, with the anterior (73%) and posterior (P2) cerebral arteries (72%) the least successfully insonated. Mean and end-diastolic blood velocities decreased significantly with age in all vessels (middle cerebral artery mean velocity: 20 to 39 years, 74 cm/s [71-76]; > 60 years, 58 cm/s [55-61], P < .0001; mean with 95% confidence intervals), and peak systolic velocity decreased significantly except in the posterior (P2) cerebral artery. Blood velocities were higher in women except in the > 60-year group. Velocities showed the least interhemispheric asymmetry in the middle cerebral artery (r = .85 and r = .83, peak and mean velocities, respectively) and the greatest asymmetry in the posterior (P2) cerebral artery (r = .58 and r = .59, peak and mean velocities, respectively). Pulsatility and resistance indices increased significantly with age in all vessels (middle cerebral artery pulsatility index: 20 to 39 years, 0.84 [0.82-0.87], > 60 years, 0.97 [0.93-1.02], P < .0001; middle cerebral artery resistance index: 20 to 39 years, 0.55 [0.54-0.56], > 60 years, 0.62 [0.60-0.64], P < .0001). Transcranial color-coded sonography can image the basal cerebral arteries and distinguish vertebral from basilar artery flow and enables pulsed Doppler interrogation with correction for the angle of insonation.

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.

A validation study on the intraobserver reproducibility of transcranial color-coded duplex sonography velocity measurements

Transcranial color-coded duplex sonography (TCCD) is a new method for the measurement of angle-corrected intracranial blood velocities. The insonation angle represents the most important technical variable affecting Doppler velocimetry. The present study was designed to evaluate the intraobserver reproducibility of TCCD for repeated examinations of blood velocity in the anterior, middle and posterior cerebral, basilar and vertebral arteries. Three examinations were performed by the same examiner in each of 20 healthy volunteers within 10 days, with a minimal interval of 2 days between two subsequent examinations. The observer was blinded to previous results. The reproducibility was evaluated by calculating the correlation coefficient ( r) and the coefficient of variance (CV) of the difference between the values obtained from the second and the third examination vs. the first examination. The results showed good reproducibility of TCCD velocity measurements in all examined arteries: for maximal systolic velocity r was 0.80–0.94 ( p < 0.001), and CV was 5.5–9.4%; for maximal enddiastolic velocities r was 0.89–0.94 ( p < 0.001), and CV was 6.6–12.2%.

Detection of superior mesenteric and coeliac artery stenosis with colour flow Duplex imaging

Measurements of blood velocity in the coeliac axis (CA) and the superior mesenteric artery (SMA) before and after a standard meal in normal people have been studied by several authors. However, information about the ability to detect stenotic lesions is lacking. The aim of our study was to determine the accuracy of Duplex scanning in detecting angiographically proven lesions. Twenty normal volunteers (13 males and seven females) and 24 patients (19 males and five females) with visceral artery stenosis on angiography were examined in the supine position (angle of insonation 60.5) with colour flow Duplex imaging (CFDI) (3.5 MHz probe), in the fasting state and after a standard meal at 15, 40, 60 and 90 min. Peak systolic velocity (PSV) and end diastolic velocity (EDV) were determined in both CA and SMA. The PSV was the best indicator of stenosis. After the meal, there was an increase in both PSV and EDV but neither of the postprandial measurements improved the accuracy of the test. The results indicate that CFDI can detect the presence of significant stenosis (> 50% in the CA and SMA with a sensitivity and specificity of > 80%.