Doppler evaluation of fetal hemodynamics

Human umbilical hemodynamics was investigated in 27 pregnant patients with gestational ages from 29 to 43 weeks using a pulsed Doppler flowmeter. The signals were analyzed by Fast Fourier Transform using a minicomputer. Coherent averaging of the signals, along with the computation of maximum velocity, mean velocity and the first moment of Fourier spectra about the zero frequency axis were performed. Hemodynamic indices were measured utilizing a comprehensive feature characterization technique of the blood flow velocity waveform. It was observed that coherent averaging reduced spectral variance thus relatively simplifying the analyses. The Pulsatility Index based on the first moment of the Fourier spectra indicated a higher umbilical flow change during the fetal cardiac cycle, than that predicted by the peak velocity Pulsatility Index. We also observed a high Pulsatility Index in association with three cases of oligohydramnios indicating the possibility of an elevated placental circulatory impedance. Variation in the peak velocity up to 20% was also noted with fetal breathing movements. Further studies are necessary to determine the clinical relevance of these findings.     

A comparison of Doppler ultrasound waveform indices in the umbilical artery--II. Indices derived from the mean velocity and first moment waveforms

Umbilical artery Doppler recordings in both normal pregnancy and cases of fetal growth failure were processed by computer. Representative waveforms for the maximum velocity, mean velocity and first moment were obtained after ensemble averaging and correction for thump filtering. The same set of indices, which included the AB ratio, pulsatility index, rising slope and relative flow rate index, were calculated for each of the waveforms. The results were compared to identify differences which might arise in clinical practice if a waveform other than the usual (maximum velocity) was used. The ratio of the mean to the maximum velocity, which gives an indication of the velocity profile, was shown to be very error prone. The reproducibility of the mean velocity and first moment indices was inferior to that of the maximum velocity indices. The results from the different waveforms were highly correlated for normals for most indices. However, in the growth retarded group there was a tendency for the mean velocity and first moment indices to classify as normal studies classified as abnormal by the maximum velocity index. The values of indices derived from the first moment waveform were generally larger than the maximum and mean velocity values. For the relative flow rate index, where results were often different to the general trend, the values were more nearly equal.     

A Doppler flowmeter for use in theatre

We have developed a Doppler flowmeter based on a 10 MHz pencil probe and mean frequency estimator which overcomes many of the limitations of existing electromagnetic and ultrasonic flowmeters. The output of the flowmeter, which is proportional to the first moment of the Doppler power spectrum and hence mean blood velocity is linear from 1.3 to over 50 cm s-1 for pulsatile flow. Variation in vessel diameter and angle of insonation, which are the common sources of error in Doppler flowmetry, are minimised by constraining the vessel in a plastic cuff which fixes the probe angle at 50 degrees. A simple gauge is used to compress the vessel flat, before the cuff is applied, to measure the wall thickness to within 0.25 mm. The vessel internal diameter and hence blood flow can then be calculated using an experimentally determined calibration factor to compensate for non-even insonation. A range of sterilizable cuffs from 3-12 mm diameter have been built and the flowmeter is now being used routinely during all arterial reconstructive surgery. The accuracy and reproducibility of the system was tested for range of different sized silastic tubes on a hydraulic model and found to be less than 12% for vessels greater than 2 mm internal diameter. Satisfactory signals were easily obtained from all prosthetic materials with the exception of PTFE. The instantaneous output was compared to an electromagnetic flowmeter using a fast Fourier transform algorithm; the moduli of the harmonics were virtually identical but the Doppler system produced a smaller phase shift with increasing harmonics.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparison of the Doppler spectra from human blood and artificial blood used in a flow phantom.

A comparison between the Doppler signals from human blood and artificial blood used in a flow phantom is described. The artificial blood used was a suspension of Sephadex particles in a glycerol solution. The Doppler power was measured as a function of Sephadex concentration and found to peak at a concentration of about 40% by volume. The power from blood was less by a factor of 150-250 than the power from Sephadex of a similar concentration. The first and second order statistics of the Doppler spectra from Sephadex were independent of particle concentration, and were very similar to those of spectra from blood.     

Influence of skin blood flow on near-infrared spectroscopy signals measured on the forehead during a verbal fluency task

Brain activity during a verbal fluency task (VFT) has been the target of many functional imaging studies. Most studies using near-infrared spectroscopy (NIRS) have reported major activation in the frontal pole, but those using PET or fMRI have not. This led us to hypothesize that changes in the NIRS signals measured in the forehead during VFT were due to changes in skin blood flow. To test this hypothesis, we measured NIRS signals and the Doppler tissue blood flow signals in the foreheads of 50 participants. The measurements were performed while each participant produced words during two 60-s periods with an interval of 100 s. In addition to a conventional optode separation distance of 30 mm (FAR channels), we used a short distance--5mm (NEAR channels)--to measure NIRS signals that originated exclusively from surface tissues. The oxygenated hemoglobin (oxyHb) concentration in the FAR and NEAR channels, as well as the Doppler blood flow signal, increased in a similar manner during the two periods of word production; the signal increase in the first period was twice as high as that in the second period. Accordingly, the mean changes in oxyHb concentration in the FAR channels were correlated closely with the changes in the NEAR channels (R(2) = 0.91) and with the integrated Doppler skin blood flow signal (R(2) = 0.94). Furthermore, task-related NIRS responses disappeared when we blocked skin blood flows by pressing a small area that covered a pair of optodes. Additionally, changes in the FAR channel signals were correlated closely with the magnitude of pulsatile waves in the Doppler signal (R(2) = 0.92), but these signals were not highly correlated with the pulse rate (R(2) = 0.43). These results suggest that a major part of the task-related changes in the oxyHb concentration in the forehead is due to task-related changes in the skin blood flow, which is under different autonomic control than heart rate.     

Prediction of brain blood flow using pulsed Doppler ultrasonography in newborn lambs

The purpose of this study was to evaluate the ability of pulsed Doppler ultrasonography to predict brain blood flow by comparing measurements made in basal cerebral arteries using a pulsed Doppler system with measurements of brain blood flow using radioactive microspheres in lambs. We measured the instantaneous maximum velocity during peak systole and end diastole and the mean velocity over the pulse cycle in basal cerebral arteries, calculated Pourcelot's index of resistance and Gosling's pulsatility index, and used regression analysis to compare the pulsed Doppler measurements with brain blood flow measured with radioactive microspheres. Pulsed Doppler measurements of the peak systolic, end diastolic, and mean flow velocity in basal cerebral arteries were directly related to brain blood flow. In contrast, no linear relationship was detected between the resistance or pulsatility indices and brain blood flow measured by microspheres (p greater than 0.14). Prediction of brain blood flow for individual subjects lacks the quantitative precision necessary for use as a clinical tool. However, the direct relationship between brain blood flow and the peak systolic, end diastolic, and mean flow velocities in basal cerebral arteries supports the use of these measurements in clinical research for the qualitative assessment of change in brain blood flow.     

Discrimination of Anterograde From Retrograde Atrial Electrograms for Physiologic Pacing

The morphology of bipolar electrograms recorded in the right atrium was examined in nine patients in an attempt to discriminate retrograde from anterograde atrial signals to an extent that would be useful for physiologic pacing. Peak-to-peak amplitude, duration, square root of energy (energy), maximum slew rate, mean slew rate, and polarity were examined in the time domain. Maximum frequency, half-power frequency, Fourier amplitude peak, and frequency of peak were measured in the frequency domain. There was a significant difference between anterograde and retrograde signals for all variables related to amplitude; these variables are peak-to-peak amplitude, energy, Fourier amplitude peak, maximum slew rate and mean slew rate. In seven of nine patients there was at least one variable sufficiently discriminating to insure reliable detection of anterograde signals while systematically rejecting retrograde signals. However, no individual variable was able to effect this discrimination in more than four patients and at least three variables were needed for all seven patients: maximum frequency, one of either energy and Fourier amplitude peak, and one of either frequency of peak or half-power frequency (six possible combinations). Thus, although differences between anterograde and retrograde atrial activity can be demonstrated in most patients, no single parameter displays sufficient discriminating power to facilitate physiologic pacing in patients exhibiting retrograde activity.     

人体心脏运动对多普勒血流速度频谱测定的影响

目的 观察多普勒血流速度频谱上的心脏运动性多普勒频移信号的幅度是否有真正代表心脏局部运动的速度,进而为纠正血流速度频谱中血流速度测量误差提供方法。方法 以心尖部为探测点,主动脉瓣环处M型超声心动图不同相位的最大运动速度为标准,观察主动脉瓣口多普勒血流速度频谱中相应相位的心脏运动性多普勒频移信号的峰值速度是否与M型测得者相关。结果 心脏运动性多普勒频谱领带不同相位的峰值运动速度与M型超声心动图所测得的相应相位的最大运动速度相关非常显著,r＝0．99。结论 根据本研究和体外模拟实验研究,血液通过各瓣口的真实峰值血流速度为血流速度频谱显示的最大血流速度与心脏运动性多普勒频移信号的峰值速度之和。     

Comparison of visually evoked peak systolic and end diastolic blood flow velocity using a control system approach.

Transcranial Doppler sonography measures blood flow velocity in basal cerebral vessels with high accuracy. For quantification, time averaged mean blood flow velocities are used most because the peak systolic and end diastolic blood flow velocities mark the velocity extremes of one heart cycle. It is known, from hemodynamic measurements of the neurovascular coupling mechanism, that the end diastolic velocity is more sensitive for change in hemodynamics than the peak systolic velocity. Thus, we used a recently introduced control system approach to compare both indices for their use in functional transcranial Doppler tests focusing on hemodynamics of blood flow velocity change. We enrolled 65 healthy young volunteers without a medical history of cardiovascular risk factors, and performed a visual stimulation test. Peak systolic and end diastolic maximal blood flow velocities were used after transformation to relative data for control-system analysis. Due to Doppler artefacts, 95% of peak systolic and 86% of end diastolic data sets were analyzed. Results showed statistically significant differences for resting blood flow velocity and the control system parameter gain, attenuation and rate time, whereas the parameters' natural frequency and time delay were equal. Increase in relative blood flow velocity in the posterior cerebral artery due to visual-cortical stimulation was higher in end diastolic values than peak systolic data. Using a complex visual stimulation paradigm, the higher sensitivity of the end diastolic index is of no practical use. Being less influenced by Doppler artefacts, the peak systolic velocity index is more feasible for control-system analysis of dynamic blood flow regulation.     

Comparison of peak and modal aortic blood flow velocities with invasive measures of left ventricular performance

The purpose of this study was to determine the accuracy of Doppler-derived modal and maximum velocity and peak and mean acceleration of ascending aortic blood for the assessment of left ventricular systolic function. Studies were performed in six anesthetized open-chest dogs. Doppler-derived modal velocity, maximum velocity, and peak and mean acceleration were compared with left ventricular dP/dt, maximum aortic blood flow, and rate of blood flow measured with an electromagnetic flow probe under varying inotropic states. Maximum Doppler velocity showed better correlation (r = 0.94, y = 0.34 + 3.95) with maximum aortic blood flow than the modal velocity (r = 0.85, y = 1.49 + 3.85x). Peak acceleration also correlated better with the rate of blood flow (r = 0.92, y = 12.3 + 4.92x) than the mean acceleration (r = 0.83, y = 12.2 + 4.27x). Modal and maximum velocity and mean and peak acceleration correlated well with left ventricular dP/dt. We conclude that peak modal and peak maximum velocity and peak and mean acceleration are accurate measurements of left ventricular function. Maximum velocity and peak acceleration are more accurate than modal velocity and mean acceleration.     

超声造影鉴别诊断原发性肝癌和肝血管瘤及肿瘤发生转移的危险因素

目的研究超声造影（CEUS）对病灶内部、周围血流信号对原发性肝癌（PHC）以及肝血管瘤（HCH）的鉴别诊断能力，并分析PHC患者肿瘤发生转移的危险因素。方法选择2019年2月~2020年12月的65例肝脏肿瘤患者作为研究对象，PHC患者35例，HCH患者30例。分别对两组患者进行CEUS检查，比较两组患者肿瘤病灶部位内部以及周围血流信号，以及相关超声指标包括增始时间、峰值时间、峰值增强强度、增强速率以及50%倾斜率的差异。比较PHC患者中不同转移情况组患者的临床资料、肿瘤病灶部位内部以及周围血流信号，以及相关超声指标差异，采用多因素logistic分析肿瘤发生转移的危险因素。结果PHC组和HCH组患者肿瘤病灶部位内部以及周围血流信号上的差异有统计学意义（P < 0.05）。PHC患者的增始时间、峰值时间、增强速率高于HCH患者，峰值增强强度以及50%倾斜率低于HCH患者（P < 0.05）。转移组与未转移组在患者的年龄、肿瘤数量、肿瘤分期上的差异有统计学意义（P < 0.05），在性别、BMI、肿瘤直径上差异无统计学意义（P > 0.05）。转移组患者与未转移组患者的血流信号的差异有统计学意义（P < 0.05）；转移组患者的增始时间、峰值时间、增强速率高于未转移组患者，峰值增强强度以及50%倾斜率低于未转移组患者，差异有统计学意义（P < 0.05）。年龄、肿瘤数量、肿瘤分期、血流信号、倾斜率、峰值增强强度、增始时间、峰值时间、增强速率均为PHC患者肿瘤发生转移的独立危险因素。结论通过对患者的超声造影检查，可有效对PHC以及HCH进行鉴别诊断，同时，年龄、肿瘤数量、肿瘤分期以及超声造影指标均可影响患者的肿瘤转移风险。      

The characterization of flow signals from tubal and ovarian arteries using intraoperative continuous wave Doppler.

Ovarian vascular Doppler is a promising screening test for early ovarian cancer detection. However, disagreements on flow indices used, flow signal shapes and ovarian vessel localization cause continuing controversy. We aimed at clarifying some of this confusion by directly measuring the adnexal arterial blood flow during laparotomy. A 10-MHz continuous Doppler probe was used to examine adnexal vessels in 24 patients undergoing laparotomy for benign gynecological pathology. Resistance (RI) and pulsatility (PI) indices were calculated for each vessel and the shape of the flow signals was noted. The tubal arteries showed a low-velocity flow pattern with relatively high end-diastolic flow when compared to the ovarian artery signals obtained from the infundibulopelvic ligament.The mean RIs for the tubal artery and ovarian artery in the infundibulopelvic ligament were 0.59 +/- 0.02 and 0.73 +/- 0.02, respectively. The mean PIs for the tubal and ovarian artery in the infundibulopelvic ligament were 1.11 +/- 0.09 and 1.53 +/- 0.1, respectively. The tubal artery showed a significantly lower RI and PI when compared to the ipsilateral ovarian artery at the infundibulopelvic ligament (p < 0.001 and p = 0.002, respectively) and its hilar branches (p = 0.03 for RI and p = 0.03 for PI). We conclude that tubal artery flow signals, which are measured directly for the first time in this study, are characteristic and are distinct from the ovarian artery signals. Tubal artery signals might be erroneously picked up during transvaginal color Doppler sonography of the ovaries, especially in the presence of conditions causing a decreased impedance to blood flow in the pelvis, such as ovarian tumors. Recognizing the flow signal from the tubal artery may help in differentiating ovarian and tubal vessels detected during color Doppler sonography.     

Normal values of fetal ductus venosus blood flow waveforms during the first stage of labor.

OBJECTIVE: To present normal values of fetal ductus venosus blood flow waveforms during the first stage of labor during and between contractions. MATERIALS AND METHODS: Seventy-eight women between the 37th and 41st weeks of gestation were included in the study. At distinct stages of cervical dilation, blood flow velocity waveforms of the fetal ductus venosus during and between contractions were visualized in fetuses with a normal non-stress test. The pulsatility index for veins, peak velocity index for veins and fetal heart rate were calculated off-line. The means +/- standard deviations (SD) during and between contractions were compared using the Wilcoxon test. RESULTS: Ductus venosus blood flow velocity waveforms were visualized during 331 contractions and 375 episodes of uterine quiescence in 74 of 78 fetuses (95%) during normal labor. The mean +/- standard deviation values of pulsatility and peak velocity indices for veins during contractions were 1.66 +/- 0.85 (median: 1.56, range: 0.29-4.69) and 1.46 +/- 0.65 (median: 1.34, range: 0.26-3.13), respectively. Between contractions the values were 0.48 +/- 0.19 (median: 0.46, range: 0.14-1.00) for the pulsatility index and 0.44 +/- 0.18 (median: 0.42, range: 0.14-1.00) for the peak velocity index for veins. These differences during and between contractions were highly significant (P-value < 0.0001), whereas the fetal heart rate showed no significant differences. CONCLUSION: There are significant differences in fetal ductus venosus blood flow waveforms during and between labor contractions. Further studies should evaluate whether these normal values of the fetal ductus venosus are beneficial for risk evaluation in fetuses with an abnormal non-stress test and/or intrauterine growth restriction.     

A vector based approach to age-related changes of Doppler velocity waveforms in the brachial artery

The shape of blood flow velocity wave has been correlated with age. The continuous wave Doppler ultrasound technique was used to obtain the blood flow velocity from the brachial arteries in 40 subjects of different age. The blood flow velocity was analysed by means of the Fourier method. The changes of relative values of harmonics were observed according to age. The second harmonic was maximum for the young and the first one for the old. To quantify these changes the vector formed from the first eight moduli was introduced. The angle between the vector so defined and a certain reference vector was accepted as a measure of the Fourier transform. Continuous alteration of wave shape described by angle has been observed according to age. The correlation between angle and age was r = 0.79 (p less than 0.001).     

Utility of color Doppler indices of dominant follicular blood flow for prediction of clinical factors in in vitro fertilization-embryo transfer cycles.

OBJECTIVE: To investigate the relationship between color Doppler indices of dominant follicular blood flow and clinical factors in in vitro fertilization-embryo transfer cycles. SUBJECTS AND METHODS: This was a prospective study involving 26 patients completing a total of 33 in vitro fertilization cycles. Dominant follicular blood flow indices, peak systolic velocities, the resistance index and the pulsatility index were evaluated using transvaginal color Doppler. The indices were compared to the clinical outcomes of in vitro fertilization-embryo transfer. RESULTS: There was a significant correlation between dominant follicular peak systolic velocities and the number of oocytes retrieved, as well as the number of mature oocytes obtained. There was no significant correlation between dominant follicular resistance index or pulsatility index and the number of follicles > 10 mm in diameter, the number of oocytes retrieved or the number of mature oocytes. There were no significant differences between dominant follicular peak systolic velocities, resistance index or pulsatility index, and fertilization rate or the ratio of good quality embryos. However, significant differences were found between the number of oocytes retrieved, as well as the number of mature oocytes for those patients in which the peak systolic velocity was below 25 cm/s. CONCLUSIONS: Doppler assessment of dominant follicle blood flow alone is useful for predicting the number of retrievable oocytes. However, morphological quality of the embryo produced or the pregnancy rate cannot be predicted by this method.     

Effects of dobutamine on coronary flow velocity response and their relations to age

The purpose of this study was to assess the effects of low-dose dobutamine on left ventricular (LV) functional and coronary flow reserves using transthracic echocardiography. The study group consisted of 30 children aged from 5 months to 16 years (mean 4.8 +/- 4.4 years). Echocardiographic studies were repeated before and during dobutamine infusion (5 microg/kg per minute). The peak diastolic velocity in the left descending coronary artery (LAD) was recorded by pulsed-Doppler under the guidance of color Doppler flow mapping. The coronary flow velocity (CFV) response was calculated as the ratio of LAD peak flow velocity at dobutamine infusion to basal LAD peak flow velocity. Left ventricular contractility was calculated by two-dimensionally directed M-mode echocardiography. The rate-corrected mean velocity of circumferential fiber shortening (mVcfc) and LV end-systolic wall stress (ESS) were used as indices of contractility. Adequate spectral Doppler recordings of the LAD peak flow velocity for the assessment of CFV response were obtained in 26 of 30 patients (87%). The LAD peak flow velocity at dobutamine infusion increased significantly compared with the basal values. The CFV response in the younger children was low and increased significantly with age. The CFV response did not show significant correlations with the changes in heart rate, systolic blood pressure, rate-pressure product, nor ESS during dobutamine infusion. However, a significant relationship between the CFV response and the percent change of mVcfc was observed. In the present study using high frequency transthoracic echocardiography, we demonstrated the age-related changes in CFV response and LV functional reserve by dobutamine infusion. Responses of LV contractility and coronary flow to dobutamine are less sensitive in youngerchildren and increased with increasing age.     

Quantitative spectral analysis of carotid Doppler signal: evaluation as a method for measurement of drug effects

Hemodynamic theories of atherogenesis suggest that the endothelial injury that initiates the process, as well as complications such as dissection and embolism, may be caused by arterial flow disturbances. Although treatment of high blood pressure prevents arteriolar complications such as brain haemorrhage and nephrosclerosis, little progress has been made in prevention of atherosclerotic events such as myocardial infarction. It is therefore desirable to develop methods for measuring the effects of antihypertensive drugs on the occurrence of such flow disturbances. We have evaluated quantitative spectral analysis of carotid Doppler signals in normals and in patients with carotid stenosis, in crossover studies of metoprolol vs placebo. Twenty healthy volunteers and 20 patients with carotid stenosis were treated in two double-blind placebo-controlled complete crossover studies, in which each subject took metoprolol 100 mg per os, and matching placebo, 1 hr before carotid scanning. In normals, peak frequency, mean frequency, and window index (WI) were measured at each of 2 sites in the left common, external and internal carotid arteries. Spectral broadening index (SBI), the ratio (peak-mean)/mean, was computed for comparison with window index (WI), the ratio of the area under the first 100 msec of the 25th percentile velocity curve to the area under the 75th percentile curve. Peak frequency, SBI and WI measure the extent of disturbance of arterial flow patterns, i.e. the extent to which flow has become non-laminar. Heart rate was reduced significantly by metoprolol, and in the external carotid artery, metoprolol significantly reduced both peak and mean frequency. Window index was not significantly changed.(ABSTRACT TRUNCATED AT 250 WORDS)     

血流切变率的多普勒估计方法

目的：研究血液动力学的一个重要参数—血流剪切率。方法：本文提出了一种利用超声多普勒技术估计血流剪切率的方法，这种方法先估计多普勒信号的平均频率曲线和最大频率曲线，然后计算血流的速度剖面，最后得到时变的血流剪切率。结果：文中还给出这方面研究的实验及结果。结论：本文提出的方法是无损估计血流剪切率的有效方法。     

Relationship between portal blood flow measured by image-directed doppler ultrasonography and hepatic blood flow measured by indocyanine green constant infusion in patients with cirrhosis

The validity of portal blood flow measurement in image-directed Doppler ultrasound (PBF-IDU) is still under debate. In this study PBF-IDU has been compared with hepatic blood flow measured by the indocyanine green constant infusion technique (HBF-ICG), which is the reference invasive method with which to measure total hepatic blood flow in man (ie, the sum of hepatic artery and portal vein blood flow). In 27 cirrhotic patients with hepatopetal portal blood flow, PBF-IDU was measured by multiplying the portal vein cross-sectional area by the averaged mean velocity of blood in the vessel. About 1 hour later HBF-ICG was measured during hepatic vein catheterization performed to evaluate portal hypertension. In 19 of 27 patients, intra-hepatic arterial resistance indices were also measured. PBF-IDU and HBF-ICG were 1.010 ± 0.555 L/min (M ± SD) and 1.496 ± 0.731 L/min, respectively. Blood flow measured by the two methods showed a close correlation (r = 0.80, p < 0.001). The regression line showed that HBF-ICG was systematically higher than PBF-IDU (mean difference + 29 ± 30%). The hepatic artery component of HBF-ICG probably accounted for the difference. An inverse correlation was found between the differences between the two procedures and intrahepatic arterial resistance indices (r = ?0.52, p = 0.04), which may be considered indirect parameters of arterial supply. It can be concluded that image-directed Doppler ultrasound is a sufficiently accurate method to measure portal blood flow in cirrhotics. © 1995 John Wiley & Sons, Inc.     

彩色多普勒血流参数对原发性与转移性肝癌的鉴别价值

【目的】探讨彩色多普勒（CDFI）血流参数对鉴别原发性肝癌（HCC）与转移性肝癌（MHC）的价值。【方法】对30例HCC和26例MHC进行CDFI检测，从两者的血流分布和血流参数方面进行对比研究。【结果】两者在血流分布上HCC肿块内部血流显示率高，两者比较差异有显著性（P〈0．05）；在血流参数上，HCC峰值血流速、阻力指数（RI）高于MHC，门静脉血流速HCC低于MHC，两者差异有显著性（P〈0．05）。【结论】CDFI血流参数在诊断和鉴别诊断HCC和MHC有较大价值。