实时灰阶二维血流显像技术的临床应用进展

实时二维灰阶血流成像技术是利用数字编码超声技术对血流、血管壁及周围软组织进行实时观察,并以灰阶方式显示的一种新型影像技术。近年来已越来越广泛地应用于颈部动脉、外周静脉、肝脏、浅表器官及产前等的检查中,成为多普勒血流检测的重要补充。     

Doppler ultrasound in the nonpregnant pelvis

The reproducibility of Doppler ultrasound waveforms within gynecology has not been previously assessed. A study was conducted of Doppler ultrasound signals from the uterine and ovarian arteries in nonpregnant women. The aim of the study was to compare the results of two different observers and also to determine the influence of a time delay (30 minutes later). A second aim was to observe the influence of the menstrual cycle on Doppler ultrasound signals. Pulsatility indices were calculated for each series of Doppler signals. The results show that the technique has a large interobserver difference and its use in the deep pelvic vessels for research purposes is of doubtful value at present.     

下肢动脉超声造影的初步研究

目的 探讨经静脉声学造影剂对下肢动脉彩色血流信号的增强作用,方法,19例患者分为2组;（1）正常组13例;（2）血管病变组6例,超声造影剂经左前臂浅静脉注射。结果 正常下肢动脉经造影剂增强后表现彩色血流信号增多,血流束增宽,4例股,国动脉闭塞者造影增强后管腔内仍无彩色血流信号,在闭塞管腔远侧,见3例胫前和1例胫后动脉内有彩色血流,上段有侧支血流进入,另2例患者胫前和颈后动脉彩色血流信号稀少,经造影增强后彩色血流信号增多并有充盈缺损,X线血管造影亦证实管腔有狭窄存在,结论 经静脉超声造影剂能够显著增强下肢动脉彩色血流信号,有助于肢血管病变的诊断。     

The use of Doppler ultrasonography for the evaluation of cerebral artery flow patterns in infants with congenital heart disease

With the use of a two-dimensional range-gated pulsed-Doppler ultrasound system, Doppler examinations of the aorta and cerebral arteries were performed in 20 normal newborn infants and in 54 infants with various forms of congenital heart disease (i.e. patent ductus arteriosus, coarctation of the aorta, critical aortic stenosis, pulmonary atresia, truncus arteriosus). In the cerebral artery Doppler recordings of the normal infants, there was antegrade flow throughout systole and diastole. In the cerebral artery Doppler recordings of the infants with cardiac disease, various abnormal flow signals (i.e. retrograde or absent diastolic flow signals, increased systolic and diastolic flow signals, etc.) were found. Furthermore, the changes in the cerebral artery Doppler recordings were concomitant with changes in the aortic Doppler flow signals and the arterial blood pressure. Representative examples of the normal and abnormal Doppler flow patterns that were observed in the aorta and cerebral arteries are presented, and the mechanisms that could lead to these flow patterns are discussed.     

Transcranial measurement of blood velocities in the basal cerebral arteries using pulsed Doppler ultrasound: a method of assessing the Circle of Willis

Transcranial pulsed Doppler ultrasound and spectral analysis were used for detection of blood velocities in the basal cerebral arteries. The Doppler transducer was placed superior to the zygomatic arch and during insonation of the middle cerebral artery care was taken to obtain maximum Doppler-shift frequency signals since this allowed a small angle between the ultrasound beam and this artery. Doppler signals were obtained from the middle, anterior, and posterior cerebral arteries in 20 volunteers with the average depth of the Doppler gate at 4.9 (4.6-5.2 cm), 5.2 (4.9-5.4 cm), and 6.3 cm (6.0-6.9 cm), respectively. These measurements were in agreement with those obtained for 15 cadaver studies, in whom the distance from the proposed site of the Doppler transducer to each basal cerebral artery was measured as 4.7 +/- 0.6, 5.3 +/- 0.5, and 5.9 +/- 0.9 cm, respectively. The reproducibility of middle cerebral artery blood velocity values was tested in seven subjects and showed a variation of not more than 8% in any individual. The method was used in combination with common carotid compression to assess four patients who had occlusive extracranial carotid disease; in three the disease was more severe on one side and reversal of blood flow in the proximal ipsilateral anterior cerebral artery was demonstrated, consistent with cross flow from the contralateral side via the anterior communicating artery of the Circle of Willis. In the fourth patient augmentation of posterior cerebral artery blood velocities during common carotid compression indicated the major collateral source was from the vertebrobasilar system.     

Vertebral arteries and neck rotation: Doppler velocimeter interexaminer reliability

The purpose of this study was to test the interexaminer reliability of Doppler ultrasound (US) velocimeter examination of vertebral arteries during contralateral cervical rotation. Vertebral arteries from 20 adults were insonated using a bidirectional Doppler velocimeter at the suboccipital portal (standard technique) and C2 transverse process level (new technique) during contralateral cervical rotation. The data obtained by two examiners, regarding persistence or major reduction in Doppler signals, were compared. There was 93% agreement between the data from the two examiners, and the kappa score was 0.78 at p = 0.05. These results provide evidence to support the interexaminer reliability of bidirectional Doppler velocimeter examination for the purpose of assessing the effects of contralateral rotation on vertebral artery blood flow.     

A method to estimate wall shear rate with a clinical ultrasound scanner

A simple technique to estimate the wall shear rate in healthy arteries using a clinical ultrasound scanner has been developed. This method uses the theory of fully developed oscillatory flow together with a spectral Doppler trace and an estimate of mean arterial diameter. A method using color flow imaging was compared with the spectral Doppler method in vascular phantoms and found to have errors that were on average 35% greater. Differences from the theoretic value for the time averaged wall shear rate using the spectral Doppler method varied by artery: brachial −9 (1) %; carotid −7 (1) %; femoral −22 (4) %; and fetal aorta −17 (10) %. Test measurements obtained from one healthy volunteer demonstrated the feasibility of the technique in vivo. E-mail: (james.blake@ed.ac.uk)     

Abnormal arterial flow pattern in untreated essential hypertension: possible link with the development of atherosclerosis

1. We compared the velocity waveforms in the superficial femoral artery measured by multichannel Doppler ultrasound in 45 subjects: 21 patients with untreated essential hypertension and 24 normal subjects of similar age and sex. 2. The pattern of arterial flow was abnormal in hypertensive patients, with the acceleration time, the duration of reverse flow and the time to maximum flow reversal being abbreviated. The internal arterial diameter, calculated from the velocity profile, was reduced despite raised pressure, suggesting altered arterial wall mechanics in essential hypertension. 3. These abnormalities will influence the wall shear stress, a major determinant of arterial function. The abnormal arterial wall mechanics and abnormal blood flow pattern may contribute to the increased risk of arterial disease in patients with untreated hypertension.     

Color Doppler sonographic mapping of pulmonary lesions: evidence of dual arterial supply by spectral analysis.

OBJECTIVE: Within pulmonary lesions, flow signals of pulmonary arteries can be discriminated from flow signals of central bronchial and peripheral bronchial arteries on color Doppler sonography. Our aim was to evaluate the evidence and frequency of different arterial supplies of pleural-based pulmonary lesions using qualitative and quantitative color Doppler sonography. METHODS: Forty-one patients with roentgenologically confirmed pleural-based pulmonary lesions were investigated by color Doppler sonography. The following parameters were investigated: (1) qualitative color Doppler sonographic evidence of vascularization, (2) quantitative color Doppler sonographic evidence of arterial flow signals (resistive index and pulsatility index), and (3) number of different arterial flow signals in 1 lesion by color Doppler sonographic mapping. RESULTS: We found no vascularization in 5 patients, sparse vascularization in 21, and pronounced vascularization in 15. Quantitative color Doppler sonographic parameters were as follows: mean pulmonary artery resistive index, 1.2; mean central bronchial artery resistive index, 0.5; mean peripheral bronchial artery resistive index, 0.7; mean pulmonary artery pulsatility index, 7.8; mean central bronchial artery pulsatility index, 0.7; and mean peripheral bronchial artery pulsatility index, 1.6. There was a significant difference between all types of flow signals for resistive and pulsatility index values but not between pulmonary and peripheral bronchial arteries (P = .068). In 41 patients, 57 different arterial flow signals were determined; 19 (46%) of these patients had 2 or more different arterial flow signals in a lesion. There was no significant difference between benign and malignant lesions regarding the number of flow signals. CONCLUSIONS: Evidence of at least a dual arterial supply can be found on quantitative color Doppler sonography in almost 50% of pulmonary lesions. A single spectral analysis is not suitable for characterization of the arterial supply of pulmonary lesions.     

Perspectives in vascular ultrasound imaging: tissue characterization, 3D reconstruction and vascular mechanics

Atherosclerosis is a variable morphologic process resulting in heterogeneous plaque components and nonuniform extent and degree of plaque deposition. We and others have developed techniques of arterial imaging, segmental reconstruction and motion analysis to determine regional vascular reactivity in arterial segments having varying and expanding degrees of atherosclerosis. We have developed and validated position registration devices (PRD) for geometric three dimensional reconstruction of coronary and peripheral arteries using intravascular ultrasound. Elaborating upon an algorithm (McKay et al.), we have developed a technique using biplane cine fluoroscopy to identify intravascular ultrasound image catheter coordinates. Initial data demonstrates clinical feasibility for accurate intracoronary three-dimensional ultrasound reconstruction. For intravascular imaging across occlusions, a prototype 20 MHz forward viewing intravascular ultrasound catheter (Cardiovascular Imaging Systems, Sunnyvale, CA) which provides a two dimensional setting distal to the catheter tip, has been developed. Transcutaneous ultrasound has been used for many years to follow atheroma progression. The use of new position registration devices allows for proper orientation such that accurate three dimensional reconstruction of the carotid bifurcation and the ilio-femoral arteries can be performed. Transesophageal echocardiography is used to evaluate different arterial beds and we have shown in familial hyperlipidemic patients undergoing LDL-apheresis, plaque progression, as determined with transesophageal echocardiography, is delayed. The accurate identification of plaque components would allow for better prediction of the effects of lipid modification regimens on plaque progression. We utilized a modified intravascular frequency device for such plaque characterization. Similarly, we are performing Doppler waveform frequency, finite element stress and finite analytic flow analysis. Data obtained from the femoral arteries to determine alterations in shear stress with expanding and eccentric atheroma. Taken together, these techniques should allow for quantitative evaluation of structural and functional characteristics of the arterial wall in different vascular beds.     

25 + 1 channel pulsed ultrasound Doppler velocity meter for quantitative flow measurements and turbulence analysis

A multichannel pulsed ultrasound Doppler instrument designed to measure velocity and volume flow rate quantitatively has been applied for turbulence detection. A 7-MHz transmitting frequency and a phase locked loop technique for the frequency to velocity conversion have been used to obtain high temporal resolution in the single channel mode. To provide for reliable positioning of the single gate within the arterial lumen the device could first be operated in the multichannel mode measuring the velocity profiles with zero crossing detection methods. Measurements of the velocity in the center of the lumen of the common and internal carotid arteries have been recorded on a beat to beat basis. An ensemble average of 16 consecutive pulses was determined. Thereafter, the root mean square of the differences between ensemble average and individual velocity pulses was computed, and a disturbance index was defined by dividing the disturbance velocity by the mean velocity. First clinical results show that the method presented is a valuable complement to the analysis of flow pulse patterns in the transcutaneous examination of carotid arteries.     

Ultrasonographic characterization of the uterine artery in the nonestrus bitch

The canine species is often used as an experimental animal model in medicine. Doppler ultrasound of uterine arteries has important clinical implications in obstetrics and gynecology in women and animal species. To our knowledge, the ultrasonographic features of uterine arteries in the bitch have not been reported. Thus, an ultrasonographic technique to locate the uterine arteries in the bitch is described in this study. A total of 11 nonspayed nonestrus bitches underwent abdominal ultrasound examination. Pulsed-wave, color and power Doppler settings were used to detect the location and characterize the flow of the uterine arteries. Mean values for systolic peak velocity, diastolic peak velocity, diastolic reversal flow and resistive index were calculated. Uterine arteries had a high pulsatility flow in all cases. Future work is needed to fully assess the clinical importance of the uterine artery flow in the bitch, as well as to study possible waveform changes at different estrus phases and throughout gestation. (E-mail: fernandoxy@yahoo.com)     

Doppler Ultrasound in Canine Pregnancy

Objective. The aim of this article is to review the current knowledge of Doppler ultrasound in canine pregnancy. A brief introduction of Doppler principles and their applications in human obstetrics is also included. Methods. A review of the peer‐reviewed published literature was conducted of the articles pertaining to the use of Doppler ultrasound in canine pregnancy, general Doppler principles, and Doppler applications in human obstetrics. Results. In bitches, Doppler ultrasound has been used to assess ovarian, uterine, umbilical, fetal aorta, common carotid artery, and fetal caudal vena cava blood flow during normal gestation. Most of these vessels increase their blood flow during normal pregnancy. The resistive index and systolic/diastolic ratio of the uterine arteries have been recently described in an experimental pharmacologically induced model of abnormal canine gestation. Both indices progressively increase up to abortion, probably because of progesterone deprivation. Moreover, resistive index abnormalities have been found in canine cases of spontaneous abnormal gestations as described in human medicine. Conclusions. Doppler ultrasound is a useful method for assessing development of the placental and fetal circulation during normal and abnormal canine pregnancy. Further studies are still necessary to widely use this technique in clinical practice.     

Transcranial Doppler in stroke.

Transcranial Doppler (TCD) has been extensively used in various clinical situations, and in the last two decades has established its role in the management of patients with cerebrovascular disease and stroke. Based on the Doppler principle, it uses ultrasound waves to insonate the blood vessels supplying the brain to obtain hemodynamic information. Anatomic abnormalities of vascular occlusion, stenosis and spasm can be indirectly derived. Intracranial arterial disease is an important cause of ischemic stroke and TCD can detect these with a fair amount of sensitivity and specificity. In hemodynamically significant extracranial internal carotid artery disease, TCD shows significant abnormalities in flow dynamics of the anterior circulation and abnormalities of cerebral vasomotor reactivity. A distinct advantage of TCD is the ability to monitor blood flow in a blood vessel over prolonged periods of time, which has shown microembolic signals in acute ischemic stroke, carotid artery disease, atrial fibrillation and during angiography. In acute ischemic stroke, TCD can be used to elucidate stroke mechanisms, plan and monitor treatment, and determine prognosis. In an era when stroke is increasingly being recognized as an emergency requiring immediate treatment, TCD may be capable of providing rapid information about the hemodynamic status of the cerebral circulation, within the time frame of the rather small 'therapeutic window'. TCD predicts vasospasm with a high degree of sensitivity and specificity and because of its non-invasive nature repeated assessments can be performed after subarachnoid hemorrhage.     

Spectral composition of Doppler signals.

The spectral content of the Doppler signal (as revealed by spectral analysis) provides useful diagnostic information about local hemodynamic conditions. Changes in these conditions are used to diagnose atherosclerotic lesions in arteries accessible to ultrasound. Extremely high frequencies, as found in and distal to a tight stenosis, indicate the presence of a jet, while Doppler signals with a wide bandwidth are related to regions with wide velocity ranges and/or disturbed flow patterns. However, the random interactions of the scatterers, the dimensions of the sample volume, the velocity of the scatterers and the method of signal processing used affect the displayed spectral composition of the Doppler signal. This article reviews the basic mechanisms and cautions the investigator against a quick and superficial interpretation of the results obtained without a proper appreciation of the random fluctuations due to the methods used to record and process the signals.     

Pancreatic metastasis: sonographic findings

BACKGROUND: Pancreatic metastasis is a relatively rare pathologic condition. Its ultrasound (US) findings have been infrequently reported, and there has been no previous report describing its color Doppler findings. METHODS: We reviewed the US findings of 13 such cases. RESULTS: The pancreatic metastasis consisted of a single hypoechoic nodule in four cases and multiple hypoechoic nodules in nine cases. US showed a slight dilatation of the main pancreatic duct in two cases of pancreatitis, and a marked biliary dilatation in one case of jaundice. The US results prompted introduction of appropriate treatment in these cases. Color Doppler US was useful for confirming the absence of flow abnormalities in the arterial and portal systems around the pancreas. In a patients with renal carcinoma metastasis, it showed many fine blood flow signals in the metastatic lesions. CONCLUSION: The role of US in the diagnosis of pancreatic metastasis consists of associated complications such as biliary dilatation or pancreatitis and detection of isolated lesions. Additional information provided by color Doppler US may increase diagnostic confidence.     

Spectrogram analysis of arterial Doppler signals for off-line automated hits detection.

Recently, a time processing of arterial Doppler signals was proposed to detect automatically high-intensity transient signals (HITS). This technique provided satisfactory detection results, but was not always constantly accurate, particularly with high-resistance blood velocity profiles. A time-frequency processing, based on the spectrogram, is presented to detect the presence of emboli in the arterial Doppler signals. The method uses the narrow-band hypothesis and extracts the detection criterion from the time-frequency representation (TFR). A first database of 560 peripheral arterial Doppler HITS was created to study microemboli and to define the normal limits to be used in our method. A threshold was experimentally defined using this database, and then applied to 38 recordings from 12 patients. Using another database, 6 human expert Doppler users reported 140, 176, 155, 161, 161 and 146 HITS, corresponding to a total of 197 different observed HITS. When an event was detected by at least 6, 5, 4, 3, 2 and 1 of the observers, sensitivity of the automatic detection was 93.9, 91.7, 89.6, 88.7, 84.7 and 73.1%, respectively. The sensitivity of our automatic detection is, thus, highly associated with the number of observers in agreement. A preliminary experiment has been performed to test the method in the case of long recording duration. In 15 patients, 6 h 24 min of recordings have been analyzed. The proposed automated processing provided an overall sensibility of 91.5%. The present work shows that this detection scheme preserves good sensibility and improves the positive predictive value compared with the time-processing recently proposed.     

Doppler ultrasound diastolic flow analysis for the early identification of peripheral arterial disease.

OBJECTIVE: The viscoelastic mechanical compliance properties of the human arterial system were examined in 100 subjects with A-mode Doppler ultrasound diastolic flow analysis. This technique of diastolic flow analysis is utilized to identify early atherogenic peripheral arterial disease. The sensitivity of the commonly utilized standard traditional ultrasound pressure-grade pneumatic cuff examination will be increased when accompanied by the diastolic flow analysis technique. SETTING: Diastolic flow analysis will aid in the early identification of lower extremity vascular claudication when lumbar spinal canal stenosis and elevated cardiovascular risk factors are present. This examination may be performed in the office setting with standard A-mode Doppler ultrasound equipment along with the usual pneumatic cuff procedure. The standard ultrasound cuff examinations are based on pressure gradients to identify lower extremity arterial disease. The low level of sensitivity of this test requires arterial obstruction of at least 50% to be present before positive identification is possible. Pathological alterations of the arterial wall occur during the early stages of atherosclerotic disease, are reflected by reduced wall distensibility and may be quantified by Doppler ultrasound. SUBJECTS: Studied were a total of 100 subjects, 50 with arterial disease risk factors and 50 normal controls. All subjects were screened for aortic coarctation, myocardial infarction, tachyarrhythmia, aortic value stenosis and mitral prolapse. The risk group subjects were all smokers and had a mixed distribution of hypertension, hypercholesterolemia and hyperglycemia. The commonly utilized standard traditional ultrasound pneumatic cuff examination was negative in all subjects. Anthropometric measurements and percent body fat were also obtained. Arterial diastolic antegrade flow analysis was performed with Doppler ultrasound on each subject. RESULTS: This study demonstrated that the elevated vascular risk factor group had a mean arterial distensibility measurement of 4.4 +/- 5.0%, and the control group displayed a mean measurement of 20.0 +/- 6.0%. The 50 elevated risk factor subjects showed approximately 5 times greater arterial stiffness and were identified with significance at an F test level of (p less than .001). CONCLUSION: This arterial compliance evaluation procedure is shown to be a reliable sensitive indicator of early atherosclerotic disease prior to the development of obstructive arterial lesions.     

Pulsed Doppler on a vaginal probe. Necessity,convenience, or luxury?

One hundred twenty-seven pregnancies were studied between 5 and 12 weeks of amenorrhea with Doppler ultrasound coupled with a vaginal probe. These biologically proven pregnancies had no clinical sign of abnormality; however, 29 were detected not to be evolving. Doppler signals were obtained from the embryonic heart, umbilical cord, trophoblastic crown, peritrophoblastic area, and from the uterine and ovarian arteries. In normally evolving pregnancies, no intratrophoblastic flow was detected, whereas it was present in all missed abortions. The peritrophoblastic area always generates a Doppler signal with an important diastolic component. The resistance index (RI) of uterine arteries was constant during the first trimester of pregnancy (RI = .77 +/- .15) and a protodiastolic notch was found in 58% of the cases. The combined use of these two modalities of examination was demonstrated. Although the clinical efficacy of the method has not yet been demonstrated, this combination of techniques opens new perspectives to echography and adds a dynamic dimension to morphologic studies.     

颈动脉体瘤的彩色多普勒超声诊断

用彩色多普勒超声对２６例共２７个颈动脉体瘤进行了研究分析，结果显示颈动脉体瘤在Ｂ型超声上主要表现为有管道的低回声，位于颈动脉分叉处，颈内外动脉间距增大，但其诊断符合率仅为７４％。彩色多普勒应用则显示瘤体内有丰富彩色血流，呈分枝、网状，脉冲多普勒显示多为动脉血流，呈低速低阻型频谱，诊断符合率可达９６％。因此，彩色多普勒超声对颈动脉体瘤的诊断有很大实用价值。