The application of CCD transversal filters for real-time spectral analysis of Doppler ultrasound arterial signals

A method of Doppler spectral analysis, based on the use of charge-coupled device (CCD) transversal filters, is described in this paper. A brief discussion of current methods of real-time spectral analysis is included, followed by a review of the theoretical basis of CCD spectral analysis. The system is detailed and the results of performance and clinical tests are presented. Carotid artery Doppler waveforms produced using the analyser illustrate the effects of flow abnormalities on the blood flow velocity waveform.     

A critical study of ultrasound Doppler spectral analysis for detecting carotid disease

The results of in vitro and in vivo studies to determine the application and limitations of frequency analysis for CW Doppler ultrasound assessment of carotid stenoses are reported. In the in vitro study, the peak Doppler frequency and a new spectral broadening index were determined proximal to, at, and distal to axisymmetric and asymmetrical model stenoses. Good correlations with percent area stenoses were found. In the clinical study, 162 cases were examined using a 4 MHz Doppler system and by standard four-vessel arteriography. Peak frequencies of greater than 3.8 KHz were diagnostic of internal carotid stenoses of 3.2 mm minimum lumen diameter or less, with a sensitivity of 92% and a specificity of 94%. Spectral broadening, evaluated by subjective grading, yielded similar results.     

A comparison of digital and analog methods of Doppler spectral analysis for quantifying flow

Ultrasonic methods can be used for calculating flow when the mean Doppler frequency is representative of spatial average velocity. We have examined the capabilities of two commercially available methods of Doppler spectral analysis for providing measurements of spatial average velocity and flow. In a steady state flow model, Doppler audio spectra were recorded using a 5-MHz duplex scanner. Fast Fourier transform (FFT) spectral analysis was used to determine mean (M), mode (MO), and maximum (MAX) frequencies. An analog method (offset zero crossing detector = ZC) was used to determine root mean square (RMS) frequencies. The results of comparing Doppler flow estimates (QM, QMO, QMAX and QRMS) with direct flow measurements (n = 10; range = 128-1098 ml/min) were (1) QM = 0.67Q + 23 ml/min (SEE = 36 ml/min); (2) QMO = 0.96Q + 152 ml/min (SEE = 32 ml/min); (3) QMAX = 1.19Q + 171 ml/min (SEE = 23 ml/min); and (4) QRMS = 0.93Q + 76ml/min (SEE = 92 ml/min). Estimates of flow using M and RMS frequencies were adversely affected by experimental conditions likely to result in turbulence. We conclude that application of commercially available FFT determined M frequencies could result in significant errors in calculations of spatial average velocity and flow. Alternatively, FFT determined MO frequencies and ZC determined RMS frequencies resulted in accurate estimates of flow in this model. This study demonstrates the importance of evaluating the capabilities of commercially available methods of Doppler spectral analysis when using ultrasound for determining velocity and flow.     

Normal pericardial fluid in the fetus: color and spectral Doppler analysis.

OBJECTIVES: To estimate the incidence of sonographic identification of pericardial fluid in normal fetuses and to evaluate the flow pattern of pericardial fluid by using color and spectral Doppler techniques. METHODS: We evaluated 27 normal fetuses for the presence of pericardial fluid by using gray-scale two-dimensional and M-mode ultrasound, and color and spectral Doppler techniques. RESULTS: Pericardial fluid was detected in 52% of cases by two-dimensional and M-mode ultrasound and in 81% of cases by color Doppler. The pericardial fluid moved towards the ventricles during systole and towards the atria during diastole. In 9 of 22 fetuses with pericardial fluid identified by color Doppler, spectral waveforms were obtained. The waveforms confirmed the bidirectional flow pattern identified at color Doppler. In six cases there was monophasic systolic and biphasic diastolic flow. In the remaining three cases, the flow was monophasic during both systole and diastole. CONCLUSIONS: Pericardial fluid can be identified with color Doppler in the majority of normal fetuses. It characteristically shows bidirectional flow as it moves with ventricular systole and diastole. Spectral waveforms can be obtained from the pericardial fluid. The presence of pericardial fluid per se should not be considered as abnormal. Color-coded pericardial fluid should not be mistaken for coronary artery blood flow.     

Quantitative analysis of carotid artery Doppler spectral waveforms: Diagnostic value of parameters

Continuous-wave ultrasonic Doppler recordings made at the carotid bifurcation have been processed by spectrum analysis and off-line microprocessor software. Data reduction algorithms were defined and tested prior to incorporation in an integrated, hard-wired device. Subsequent analysis of waveforms in real-time provided measures of peak and mode frequencies and degree of spectral broadening.Correlation of results with 123 angiographically visualized internal carotid arteries showed that peak and mode frequencies generally increased with degree of stenosis while the systolic window decreased. Ratios of peak and mode frequencies in the proximal to the distal internal carotid artery and the systolic window at the distal internal carotid artery were retrospectively found to have diagnostic value with a combination of these three parameters providing the best overall accuracy     

Selection of the order of autoregressive models for spectral analysis of Doppler ultrasound signals

Autoregressive modelling includes a model identification procedure, that is, it is necessary to choose the order of the autoregressive (AR) process that best describes the given finite record (frame) of the signal. Four previously suggested procedures to choose the "best order" of AR processes have been tested: The "first zero crossing" of the autocorrelation function (FZC), the "final prediction error" (FPE), "Akaike's information criterion" (AIC), and the "criterion autoregressive transfer-function" (CAT). It was found that: (i) For more than 98% of the 1280 frames of Doppler signals analyzed the order selected by the various criteria was ten or less. (ii) For the same records of Doppler signals, FPE, AIC and CAT behave in a very similar manner, but the FZC criterion underestimates the order in relation to the others. (iii) For true AR processes, the order selected is frequently different from the true AR order when frames of 64 samples are used. When more samples are used FPE, AIC and CAT tend to select the correct order. (iv) The effect on the spectral estimate of using too high a model order is usually insignificant, while using too low an order can change the estimate more dramatically, that is, overestimating the model order is better than underestimating it.     

Transvaginal imaging: applied physical principles and terms

In this article the properties of ultrasound in tissues and the factors governing image quality are discussed. Particular emphasis is placed on the vaginal probe. The virtues of transvaginal scanning both in gynecology and obstetrics are well described in subsequent articles in this symposium. Only by understanding the properties of ultrasound can the capabilities and limitations of this technique be appreciated. A comprehensive knowledge of the basic physical principles is mandatory for the clinician as well the investigator to attain the highest quality results. The technical aspects of operating ultrasound instruments, e.g., machine controls, electronic image formation, scan converters and techniques for preprocessing and postprocessing, are not discussed.     

频谱多普勒超声诊断椎基底动脉供血不足的价值

目的 探讨椎基底动脉系统脑血流量和椎基底动脉收缩期峰值流速在频谱多普勒超声诊断椎基底动脉供血不足(VBI)中的价值.方法 将107例临床怀疑椎基底动脉供血不足患者分为三组:重度VBI组、轻一中度VBI组和非VBI组.分别检测椎动脉和基底动脉二维图像和血流频谱,比较椎动脉、基底动脉收缩期峰值流速和椎基底动脉系统脑血流量在诊断椎基底动脉供血不足中的差异.结果 椎动脉和基底动脉收缩期峰值流速在重度VBI组患者中明显低于轻-中度VBI组,差异有统计学意义(P＜0.05);在轻-中度VBI组患者中低于非VBI组,但差异无统计学意义(P＞0.05).结论 脑血流量在判定患者是否为椎基底动脉供血不足及程度上有诊断价值,可以作为超声诊断VBI的有效指标.     

Ultrasound Doppler spectral analysis in the diagnosis of occlusive lesions of the carotid arteries.

To evaluate the accuracy of Ultrasound Doppler Spectral Analysis (USDA), 432 carotid arteries were examined [group I consisted of 145 cases of normal ICA (internal carotid artery), group II--187 cases of ICA stenosis and group III--100 cases of ICA occlusion]. The maximal systolic peak (Smax), maximal diastolic peak (Dmax), the spectral broadening index (SB) and the pulsativity index (PI) were calculated and related to the degree of stenosis as determined by contrast arteriography. Our results indicate that the change of the value of Smax is the main diagnostic criterion: for carotid arteries' stenoses, it increases to over 3.2 kHz. A Smax over 6.0 kHz is a veritable index of ICA stenosis above 50%: in such cases as the stenosis increases by 10%, this corresponds to an approximately 1 kHz increase of Smax. In ICA occlusion, the main criterion was the absence of blood flow in the distal ICA segment. The UDSA sensitivity in hemodynamically insignificant stenosis is 73.9% which is far higher than in the periorbital Doppler examination; in hemodynamically significant stenosis and ICA occlusions, the sensitivity is 98.6 and 99%, respectively.     

乳腺癌多普勒血流频谱特征及与微血管密度和肿块转移的相关性

目的探讨乳腺癌多普勒血流频谱特征及其与微血管密度(MVD)和肿块转移的相关性.方法术前1周对144个乳腺良恶性肿块患者的原发灶行彩色多普勒超声扫查,观察肿块多普勒血流频谱特征,并测定血流动力学参数:收缩期血流峰值流速(PV)及加速时间(AT).采用免疫组织化学两步法对获取的乳腺癌标本行免疫组化研究,并检测MVD.结果乳腺癌病变的收缩期血流频谱表现为PV增快、AT缩短及峰值前移;舒张期频谱形态变化较大,根据舒张期流速降幅及持续时间把90例乳腺癌病变的舒张期多普勒血流频谱分为Ⅰ型(30例)、Ⅱ型(20例)、Ⅲ型(17例)、Ⅳ型(23例).4型乳腺癌患者的肿块内MVD呈上升趋势,Ⅲ型和Ⅳ型明显高于Ⅰ型.在转移组和未转移组,4型舒张期多普勒血流频谱类型在构成上存在差异,未转移组以Ⅰ型、Ⅱ型为主,转移组中4型所占比例相似.结论乳腺肿块多普勒血流频谱特征在鉴别乳腺肿块良恶性及判断是否转移有重要意义.     

Use of colour and spectral Doppler ultrasound examination in gynaecology

Objective: To review and sum up the published literature on gynecological Doppler ultrasound examination. Methods: Publications on gynecological Doppler ultrasound examination already known by the author, publications found in the bibliographic database Medline, and publications found in the reference lists of available studies were read, and relevant information was extracted and summarized. Results: Reference data representative of normal findings at transvaginal color and spectral Doppler ultrasound examination of the uterine and ovarian arteries have been established in healthy pre- and post-menopausal women and in normal early pregnancies. Blood flow velocities in the uterine and ovarian arteries change during the normal menstrual cycle and are very different in pre- and post-menopausal women. Lower blood flow velocities and higher pulsatility index (PI) values have been recorded in the ovarian arteries after the menopause. Uterine artery blood flow velocities increase and uterine artery PI values and resistance index (RI) values decrease with gestational age in the first trimester. There is not yet an established role of the gynecological Doppler ultrasound examination in clinical practice. It remains unclear whether the gynecological Doppler ultrasound examination contributes substantially to the clinical management of early pregnancy complications or infertility problems, to the differential diagnosis of pelvic masses or uterine pathology. Conclusions: Large prospective studies—preferably randomized controled trials—are needed to determine the clinical value of the gynecological Doppler ultrasound examination.     

乳腺肿块的彩色多普勒血流频谱形态与病理对照研究

目的 探讨乳腺肿块的彩色多普勒血流频谱形态与其病理性质之间的相关性，以提高超声对乳腺肿块的诊断符合率。方法 对116例乳腺良、恶性肿块进行彩色多普勒超声检测，检测结果与病理结果进行对照分析。结果 ①乳腺恶性肿块彩色多普勒血流频谱形态常表现为：收缩期峰值速度前移，常出现于收缩期的前三分之一时段；收缩期上升及下降速度均较快，表现为上升波和下降波陡直；舒张期起始波常出现于收缩期下降波的中点以下，舒张末期常无血流或出现反向血流频谱。②乳腺良性肿块彩色多普勒血流频谱形态为收缩期峰值速度常居中，出现于收缩期的中三分之一时段；收缩期上升及下降速度均较慢，表现为上升波和下降波倾斜；舒张期起始波常出现于收缩期下降波的中点以上，舒张末期常出现血流频谱。结论 彩色多普勒血流频谱形态是鉴别乳腺良、恶性肿块的一项值得重视的指标。     

Implementation of spectral width Doppler in pulsatile flow measurements

In this paper, we present an automatic beam-vector (Doppler) angle and flow velocity measurement method and implement it in pulsatile flow measurements using a clinical Doppler ultrasound system. In current clinical Doppler ultrasound flow velocity measurements, the axis of the blood vessel needs to be set manually on the B-scan image to enable the estimation of the beam-vector angle and the beam-vector angle corrected flow velocity (the actual flow velocity). In this study, an annular array transducer was used to generate a conical-shaped and symmetrically focused ultrasound beam to measure the flow velocity vectors parallel and perpendicular to the ultrasound beam axis. The beam-vector angle and flow velocity is calculated from the mode frequency (f(d)) and the maximum Doppler frequency (f(max)) of the Doppler spectrum. We develop a spectrum normalization algorithm to enable the Doppler spectrum averaging using the spectra obtained within a single cardiac cycle. The Doppler spectrum averaging process reduces the noise level in the Doppler spectrum and also enables the calculation of the beam-vector angle and flow velocity for pulsatile flows to be measured. We have verified the measurement method in vivo over a wide range of angles, from 52 degrees to 80 degrees, and the standard deviations of the measured beam-vector angles and flow velocities in the carotid artery are lower than 2.2 degrees and 12 cm/s (about 13.3%), respectively.     

Rapid spectral analysis for spectral imaging

Spectral imaging requires rapid analysis of spectra associated with each pixel. A rapid algorithm has been developed that uses iterative matrix inversions to solve for the absorption spectra of a tissue using a lookup table for photon pathlength based on numerical simulations. The algorithm uses tissue water content as an internal standard to specify the strength of optical scattering. An experimental example is presented on the spectroscopy of portwine stain lesions. When implemented in MATLAB, the method is ~100-fold faster than using fminsearch().     

Display of spatially-registered Doppler spectral waveforms and three-dimensional vein graft geometry

A method has been developed to display Doppler spectral waveforms in lower extremity vein grafts in conjunction with 3-D vessel geometry. Doppler spectral waveforms and cross-sectional images of the vein graft are collected with a custom 3-D ultrasound imaging system. Computer processing generates a display of the Doppler sample volumes registered in 3-D space with a surface reconstruction of the vein graft lumen. An interactive computer interface displays spectral waveforms at user-selected sites in the graft. Summary displays combining spectral waveforms, maximum velocity and cross-sectional area provide a pictorial record of the state of the vein graft along its full length. The method is demonstrated for two patient studies, each at two time points after graft revisions. The graphic display of both hemodynamics and geometry allows rapid assessment of vein graft changes over time.     

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)