Characterization of volumetric flow rate waveforms in the normal internal carotid and vertebral arteries

Knowledge of normal cerebrovascular volumetric flow rate (VFR) dynamics is of interest for establishing baselines, and for providing input data to cerebrovascular model studies. Retrospectively gated phase contrast magnetic resonance imaging was used to measure time-resolved VFR waveforms from the two internal carotid arteries (ICA) and two vertebral arteries (VA) of 17 young, normal volunteers (16M:1F) at rest in a supine posture. After normalizing each waveform to its respective cycle-averaged VFR, the timing and amplitude of feature points from the individual waveforms were averaged together to produce archetypal ICA and VA waveform shapes. Despite significant inter-individual differences in cycle-averaged VFR within the ICA compared to VA (275+/-52 versus 91+/-18 mL min-1), the respective waveform shapes were qualitatively similar overall. The VA waveform shape did, however, exhibit significantly higher amplitudes (e.g., peak:average VFR of 1.78+/-0.30 versus 1.66+/-0.16; p<0.05) and significantly higher variability both between and within subjects. A significant correlation was observed between peak and cycle-averaged VFR, suggesting that the representative waveform shapes presented here-when scaled by an individual's cycle-averaged VFR-may be used to characterize normal ICA and VA flow rate dynamics. This capability may be of particular utility for studies where cerebrovascular flow dynamics are required, but only average flow rates are available.     

Changes in Doppler waveforms can predict pressure reduction across internal carotid artery stenoses

Cerebral ischemia can result from either embolism or be due to hemodynamic failure. The purpose of this study was to evaluate whether Doppler waveforms, obtained distal to an internal carotid artery (ICA) stenosis, could predict the degree of hemodynamic compromise in terms of reduction in cerebral perfusion pressure. Forty-nine patients were examined consecutively with ultrasound Doppler prior to carotid endarterectomy. Pulsatility index (PI), pulse rise-time (RT), and systolic width (SW) were related to angiographic degree of stenosis and the ratio of distal ICA blood pressure to common carotid artery (CCA) blood pressure (ICA/CCA pressure ratio). The latter was determined during surgery. All three waveform parameters were significantly correlated with the ICA/CCA pressure ratio when calculated from the mean frequency curve (p less than 0.001). A reduction in ICA pressure of 20% could be predicted with an accuracy of 90-95%. Correlating the waveform parameters with arteriography was less convincing, reaching the level of statistical significance for PI only. ICA Doppler waveforms, obtained as distal in the neck as possible can accurately predict the degree of hemodynamic compromise. It is recommended as a simple adjunct to routine Doppler evaluation of carotid stenoses.     

Doppler sonography of normal fetal vertebral and internal carotid arteries during pregnancy

PURPOSE: The aim of this study was to determine the resistance index (RI) in the fetus in both the vertebral artery and the internal carotid artery and to evaluate the relationship of those RIs with that of the umbilical artery. METHODS: In this prospective study, color Doppler examinations of the vertebral, internal carotid, and umbilical arteries were performed in fetuses with normal growth between 17 and 41 weeks' gestational age. For every week, the 10th, 50th, and 90th percentiles of the RIs in the 3 arteries plus the ratios of the RIs of the vertebral and umbilical arteries and of the internal carotid and umbilical arteries were calculated. RESULTS: In 225 examinations in 114 women, the vertebral and internal carotid arteries showed similar RI patterns, with higher RIs at mid gestation. The only difference was that the RIs in the internal carotid artery reached maximum values at a slightly later gestational age (26-28 weeks) than did those in the vertebral artery (24-25 weeks). Also, the RIs in the vertebral artery were slightly higher than were those in the internal carotid artery. RI values in the umbilical artery decreased progressively throughout gestation. Conversely, the ratios of the RIs in the vertebral and umbilical arteries and those of the RIs in the internal carotid and umbilical arteries increased slightly until the end of pregnancy, with the former ratios always higher than the latter ones. CONCLUSIONS: In normal fetuses, the pattern of blood flow resistance in the vertebral artery resembles that in the internal carotid artery. However, compared with the internal carotid artery, the vertebral artery shows higher absolute RIs with maximum values appearing earlier in the course of pregnancy.     

彩色多普勒超声鉴别诊断颈部神经鞘瘤和颈动脉体瘤

目的 探讨彩色多普勒超声对颈部神经鞘瘤和颈动脉体瘤的鉴别诊断价值.方法 回顾性分析18例经手术病理证实的颈部神经鞘瘤和颈动脉体瘤的彩色多普勒超声表现.结果 神经鞘瘤均为单发的实质性低回声肿物,可伴有囊性变,呈类圆形,边界清晰,有包膜,内部可探及点状或线状血流信号,呈高阻型动脉血流频谱;颈动脉体瘤为单侧或双侧发生的位于颈总动脉分叉处的实质性低回声肿物,使颈内外动脉间间距增大,包绕颈总动脉和(或)颈内外动脉,内部血流极为丰富,呈低阻型动脉血流频谱.结论 彩色多普勒超声对颈部神经鞘瘤和颈动脉体瘤的鉴别诊断具有重要的临床应用价值.     

Doppler waveforms in the renal arteries of normal children

Blood velocity waveforms in peripheral arteries vary such that decreasing vascular resistance results in a relative increase in diastolic velocity at steady state. We measured blood velocity in renal arteries of 20 children (age: 119 months ± 37 months; weight: 38 kg ± 15 kg) to establish normal values, and to explore the relationship between these waveforms and central hemodynamics. Using image-directed pulsed Doppler echocardiography, M-mode measurements and cardiac index were recorded. Renal hila were visualized via the flank for Doppler sampling. Peak systolic velocity (A) and minimal diastolic velocity (B) were determined. The results (mean ± SD) were as follows: Renal artery A/B = 2.9 ± 0.74 (range 1.9 to 5.1). Characteristic waveforms were identical bilaterally and had continuous diastolic foward flow: A/B was independent of central hemodynamics within the resting normal range, varying inversely with age and size.     

Color Doppler characteristics in normal lower extremity arteries.

The purpose of this study was to determine the normal characteristics of the lower extremity arterial system as seen with color Doppler. A total of 420 arterial segments from the level of the proximal abdominal aorta to the distal tibial and peroneal vessels were examined with a color ultrasound scanner in 10 normal volunteers. Each arterial segment was examined for the presence of triphasic flow, wall irregularities, calcification, bruits, collaterals, and post-stenotic flow patterns. Standard duplex spectral waveform data were also obtained at each site. As expected, triphasic flow was present and detected by color Doppler in the majority of arterial segments. Color patterns suggesting the presence of bruits, collaterals, or post-stenotic flow were absent in all cases.     

Color Doppler artifact from metallic carotid clamp.

The presence of mirror artifacts in color Doppler has been noted by others. In that report, the artifact arose from scattering at the smooth vessel wall and appeared as signal outside the lumen of the vessel, but with no change in flow direction. As experience increases, recognition of the artifacts of color Doppler will lead to a better understanding and more precise evaluation. This case shows that a band of metal around the carotid artery causes registration errors in color-coded Doppler, and perhaps other metal foreign bodies in the soft tissues have similar potential. The specific appearance of the artifact will depend sensitively on the geometrical configuration of the metal body itself and on its orientation relative to the surrounding anatomy and the ultrasound probe. Appropriate placement of the transducer will reduce such artifact.     

Flow-area relationship in internal carotid and vertebral arteries

Subject-specific computational and experimental models of hemodynamics in cerebral aneurysms require the specification of physiologic flow conditions. Because patient-specific flow data are not always available, researchers have used 'typical' or population average flow rates and waveforms. However, in order to be able to compare the magnitude of hemodynamic variables between different aneurysms or groups of aneurysms (e.g. ruptured versus unruptured) it is necessary to scale the flow rates to the area of the inflow artery. In this work, a relationship between flow rates and vessel areas is derived from phase-contrast magnetic resonance measurements in the internal carotid arteries and vertebral arteries of normal subjects.     

Examination of carotid arteries with quantitative color Doppler flow imaging.

The results of conventional duplex scanning were compared with QCDFI. A total of 224 consecutive patients comprising 442 unilateral carotid systems were examined by conventional duplex techniques. MPSV, as determined by QCDFI, were recorded for each of the 442 carotid segments and grouped according to the previously determined degrees of stenosis. The predictive value of QCDFI was confirmed by angiography with an overall accuracy of 91%. Results obtained by duplex scanning correlated with angiography 89% of the time. Based on QCDFI data, a scale to grade carotid stenosis was developed.     

Agenesis of the internal carotid artery: Color Doppler,CT, and MR angiography findings

Agenesis of the internal carotid artery (ICA) is a rare finding that can lead to the false diagnosis of an ICA occlusion. We present the case of a young woman with agenesis of the left ICA. Diagnosis was made noninvasively by color Doppler imaging (CDI) in combination with high-resolution CT of the base of the skull. Magnetic resonance angiography confirmed the diagnosis. CDI in combination with CT of the base of the skull allows the diagnosis of ICA agenesis without the use of invasive procedures. © 1998 John Wiley & Sons, Inc. J Clin Ultrasound 26:213–216, 1998.     

胎儿脐、肾血流的彩色多普勒检测

本文利用彩色多普勒对５４例中、晚孕胎儿脐、肾动脉血流频谱进行了观察及分析，结果表明：随着孕龄的增加，胎儿的脐、肾动脉的血流参数及二者的比值有一定的变化规律，妊高症及胎儿宫内发育迟缓者则出现异常。     

B-flow imaging in low cervical internal carotid artery dissection.

OBJECTIVE: Generally, the vascular ultrasonographic examination is the first method in evaluation of internal carotid artery (ICA) dissection. B-flow imaging (BFI), conversely, is a newer method of vascular ultrasonography. The objective of this study was to assess the accuracy and efficacy of BFI for the diagnosis of low cervical ICA dissection. METHODS: Seventeen consecutive patients with 18 angiographically confirmed low cervical ICA dissections and 16 nondissected ICAs were studied with BFI and color Doppler ultrasonography (CDU). The results were compared with those of digital subtraction angiography. RESULTS: The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of BFI in diagnosis of low ICA dissection were 94%, 94%, 94%, 94%, and 95%, respectively. Corresponding results for CDU were 83%, 94%, 94%, 83%, and 88%. B-flow imaging more precisely showed the intimal flap and the visualization of flow within the true and false lumens. In dissected carotid arteries, 6 intimal flaps were diagnosed with CDU, and 15 intimal flaps were diagnosed with BFI. The agreement between the observers in determining low cervical ICA dissection by BFI was found to be excellent (kappa = 0.80 for intramural hematoma; kappa = 0.93 for intimal flap). CONCLUSIONS: B-flow imaging seems to be a new reliable vascular ultrasonographic technique for evaluation of low cervical ICA dissection.     

Doppler sonography evaluation of flow velocity and volume of the extracranial internal carotid and vertebral arteries in healthy adults

PURPOSE: To measure with Doppler sonography the velocity and volume of blood flow in the extracranial internal carotid artery (ICA) and vertebral artery (VA) of healthy adults and to calculate total cerebral blood flow volume (tCBFV). METHODS: Bilateral ICA and VA were examined sonographically in 180 healthy adults. Angle-corrected peak systolic (Vps), end-diastolic (Ved), and time-averaged maximum blood flow velocity (TAV) were measured in pulsed Doppler mode, and the resistance index (RI) and pulsatility index (PI) were calculated. The cross-sectional area (A) was measured on gray-scale images. Volume flow was calculated as FV = TAV x A, and tCBFV was calculated as the sum of the right and left ICA and VA volume flow. RESULTS: tCBFV was 651 +/- 96 ml/min for the entire population. There was a significant decrease in Vps, Ved, TAV, and tCBFV with age in all arteries. RI and PI values initially declined and then increased with age. Cross-sectional area increased with age in ICA but not in VA. PI and RI were higher in men than in women. Blood flow velocity and volume were higher, and RI was lower in the left than in the right VA. CONCLUSION: The Doppler sonographic assessment of extracranial ICA and VA blood flow volume may be useful for the study of cerebral hemodynamic changes in patients with cerebrovascular disorders. Age-dependent changes should be considered, for instance, in the management of intensive care patients with impaired cerebral perfusion.     

Continuous and simultaneous ultrasound Doppler velocimetry of the internal carotid and vertebral arteries: preliminary observations of cerebral blood flow changes with common carotid compression.

We have developed a new technique for simultaneous assessment of the four cervical cerebral arteries. Using a cervical brace with four freely adjustable Doppler probes attached, we studied four healthy young males and observed their cerebral blood flow changes during common carotid compression. The results indicated various reactivity in these subjects. We observed that carotid compression sometimes affects or stops the ipsilateral vertebral flow according to the intensity and location of compression. Also, the flow of the contralateral internal carotid artery (ICA) and vertebral artery (VA) showed remarkable increases greater than those due to ICA obliteration alone. This indicates the possibility that using only one probe during compression may often result in unknown obliteration of the ipsilateral VAs flow and could also produce other incomplete data. Moreover, with our technique, we would be able to assess the cerebral reserve more precisely and clearly in patients with carotid or vertebral occlusive diseases.     

Color Doppler ultrasonography in occlusive diseases of the brachiocephalic and proximal subclavian arteries.

OBJECTIVE: The purpose of this study was to investigate the capability of color Doppler ultrasonography (CDU) in showing the brachiocephalic and proximal subclavian arteries and to determine the accuracy of CDU for diagnosis of occlusive diseases of those arteries. METHODS: Two groups of patients were examined. The first group was examined with CDU to determine whether the brachiocephalic and subclavian artery origins could be seen. The second group, including patients with occlusive arterial disease, was examined with CDU before digital subtraction angiography (DSA). Results of CDU and DSA were compared. RESULTS: In the first group, the origins of 42 (84%) of 50 brachiocephalic arteries, 48 (96%) of 50 right subclavian arteries, and 25 (50%) of 50 left subclavian arteries could be displayed by CDU. In the second group, 8 (89%) of 9 lesions on the right and 23 (96%) of 24 lesions on the left were diagnosed correctly. Color Doppler ultrasonography had sensitivity, specificity, positive predictive value, negative predictive value, and accuracy values of 88%, 94%, 78%, 97%, and 94%, respectively, for detecting major stenosis and 100%, 98%, 94%, 100%, and 99% for detecting occlusion. Agreement between the CDU and DSA findings was substantial for stenosis (kappa = 0.78) and almost perfect for occlusion (kappa = 0.96). CONCLUSIONS: The percentage of proximal left subclavian arteries shown on CDU was considerably lower compared with the right subclavian and brachiocephalic arteries. However, there was no significant difference between the two sides in diagnosing occlusive arterial diseases. With CDU, occlusion can be diagnosed more accurately than stenosis.