Analysis Of Doppler Signals Research Articles

Real-Time Spectral Analysis of Brachial Doppler Signals in Neonates with Patent Ductus Arteriosus

Twenty-three Doppler examinations of the brachial artery were performed on 10 infants with patent ductus arteriosus (PDA). The continuous-wave (CW) zerocrossing recordings were compared with the waveforms obtained from spectral analysis (SA) of the audio signal from the CW flowmeter by means of the pulsatility index (PI). The CWPI correlated well with the SAPI (r = 0.89, P < 0.001). The patients were easily grouped into those infants who were normal or had clinically insignificant PDA's from those with a significant PDA using the PI. Although spectral analysis can detect and prevent sampling artifacts, the CW zero-crossing detector provided clinically-useful information.

Analysis of ultrasound Doppler velocimeter signals using a personal computer

A method for the rapid on-line analysis of Doppler signals obtained transcutaneously by continuous wave ultrasound is described. The system, which employs a digital spectrum analyser and a personal microcomputer, calculates and displays pulsatility index derived from either the maximum or the mean frequency envelopes. Storing reduced data in the form of standardized waveforms provides for a posteriori analysis.

Effect of quantitated stenoses on arterial sound spectrum analysis

Spectral analysis of carotid Doppler signals has been shown to be accurate in determining the degree of carotid artery stenosis when compared with arteriography. Since the Doppler angle and the amount of gain used during measurement may affect results, an in vitro study was performed measuring peak frequency, mode frequency, and percent window at various Doppler angles and gains to determine if these latter factors could affect results of the test. A spectrum analyzer with an 8 MHz continuouswave Doppler probe was utilized. Seven cross-sectional area stenoses (0 to 100 percent) were applied to an undiseased bifurcated cadaver artery which was suspended in a saline bath and placed in a pulsatile circulatory system. At each stenosis, peak frequency, mode frequency, and percent window were measured at three Doppler angles (45 degrees, 60 degrees, and 75 degrees) at a constant gain and at three different gains (low, medium, and high) at a constant Doppler angle of 60 degrees. Arterial pressure was measured distal to the stenoses. Critical stenoses were present at greater than 82 percent area reduction. At a Doppler angle of 60 degrees and medium gain, correlation coefficients between percentage of stenosis and peak frequency, mode frequency, and percent window were 0.9520, 0.8369, and −0.9861, respectively. However, peak frequency and mode frequency actually decreased at stenotic areas of more than 82 percent and were similar to frequencies seen at stenotic areas of 61 percent. Peak frequency significantly decreased as Doppler angle increased, so there was an even greater overlap of peak frequency values at larger angles. Percent window did not appear to be affected by Doppler angle. At an angle of 60 degrees and different gains, there appeared to be very little overlap of percent window values between any stenoses. Peak frequency and mode frequency did not appear to be affected by gain. This study demonstrates an excellent correlation between percentage of stenosis and peak frequency and percent window. However, peak frequency was significantly affected by changes in Doppler angle and did not differentiate subcritical (61 percent) from critical (96 percent) stenoses. Percent window, however, was not significantly affected by Doppler angle or gain and was able to differentiate between all degrees of stenosis.

Recording Doppler blood flow signals on magnetic tape

A European multi-centre trial of blood flow measurement by ultrasound has been organised under the auspices of the biomedical engineering programme of the European Community (Beneken et al., J. Med., Eng. Tech., vol.9, p.61-8, 1985). The programme includes analysis of Doppler blood flow signals that have been recorded on cassette tapes using standard domestic tape recorders. A pilot study has shown that the standard of the data replayed from tape is very variable and this communication examines the reasons for this, and suggests a solution.

Doppler developments in the last quinquennium

The major advances which have taken place during the last five years in the development of ultrasonic Doppler devices and methods of Doppler signal analysis are reviewed. The following aspects of instrumentation are considered: crossed beam Doppler systems, range measuring Doppler systems, duplex systems, flow mapping systems, transducers and measurements of system performance. Analytical methods are discussed in the following categories: waveform analysis, including the extraction of single-value waveforms and their applications to the diagnosis of vascular disease; spectral analysis, including the derivation of frequency spectra and their application in the study of blood flow; and volume flow estimation. It is concluded that it is likely to be in the study of the information in Doppler frequency spectra, two-dimensional real-time Doppler images and in the measurement of blood flow volume that most progress will be made.

Prediction of carotid disease by ultrasound and digital subtraction angiography.

Ultrasound (US) technology (B-mode real-time imaging and Doppler signal analysis) and digital subtraction angiography (DSAV) were prospectively compared in 90 consecutive patients. Twenty-four endarterectomy specimens became available. The DSAV was uninterpretable in 9.4% of vessels and US, in 8.3%. Estimation of degree of stenosis by both modalities agreed well with endarterectomy specimens. Neither predicted the presence or absence of ulceration accurately. Not considering occlusions (where DSAV is probably more accurate), no clear superiority as a screening test compared against a common standard was demonstrated for either. In all 148 vessels with adequate studies by both, the technologies agreed in categorizing stenosis (less than or equal to 50% v greater than 50% diameter stenosis) in 89%. Correlation was poor for occlusions and ulceration. If DSAV were definitive, US would be an effective screen for surgically relevant stenosis with a negative predictive value of 95%.

The contribution of spectral analysis to the diagnosis of carotid artery disease

Pulsed and continuous-wave Doppler examinations with spectral analysis were performed on 258 carotid arteries in 220 patients and compared with multiplane contrast angiography. Each artery was examined for stenosis and assigned to one of four groups: normal to 19%, 20% to 49%, 50% to 99%, and occlusion. The incidence of disease was 70%. Diagnostic sensitivity with all noninvasive techniques varied from 76% to 90% depending on the degree of stenosis, with an overall accuracy rate of 86%. In an attempt to evaluate the diagnostic contribution of spectral analysis, stenosis classification by peak frequency alone was compared with that of the full laboratory profile, including spectral analysis. In the 147 carotid arteries in which such data were available, diagnostic sensitivity was improved with spectral analysis by 8% to 29% depending on the degree of stenosis. Detection of occlusions was unchanged. The major contribution of spectral analysis was in detecting non-flow-limiting stenoses of 20% to 49%. Spectral analysis added little to the diagnostic ability of peak frequency to detect lesions with >50% stenosis. Spectral analysis of either pulsed Doppler or continuous-wave Doppler signals is an accurate noninvasive method for evaluating carotid bifurcation disease, which particularly improves the detection of non-flow-limiting stenoses.

The contribution of spectral analysis to the diagnosis of carotid artery disease.

Pulsed and continuous-wave Doppler examinations with spectral analysis were performed on 258 carotid arteries in 220 patients and compared with multiplane contrast angiography. Each artery was examined for stenosis and assigned to one of four groups: normal to 19%, 20% to 49%, 50% to 99%, and occlusion. The incidence of disease was 70%. Diagnostic sensitivity with all noninvasive techniques varied from 76% to 90% depending on the degree of stenosis, with an overall accuracy rate of 86%. In an attempt to evaluate the diagnostic contribution of spectral analysis, stenosis classification by peak frequency alone was compared with that of the full laboratory profile, including spectral analysis. In the 147 carotid arteries in which such data were available, diagnostic sensitivity was improved with spectral analysis by 8% to 29% depending on the degree of stenosis. Detection of occlusions was unchanged. The major contribution of spectral analysis was in detecting non-flow-limiting stenoses of 20% to 49%. Spectral analysis added little to the diagnostic ability of peak frequency to detect lesions with greater than 50% stenosis. Spectral analysis of either pulsed Doppler or continuous-wave Doppler signals is an accurate noninvasive method for evaluating carotid bifurcation disease, which particularly improves the detection of non-flow-limiting stenoses.

Blood flow in deep abdominal and pelvic vessels: ultrasonic pulsed-Doppler analysis.

Ultrasonic pulsed-Doppler signals from deep-lying vessels in the normal abdomen and pelvis are described. The signal characteristics combine to produce a Doppler "signature" that is specific for each vessel. The clinical potential of this method of deep flow detection is considered in relation to three areas of Doppler signal analysis: first, qualitative indication of the presence, direction, or absence of flow in a structure; second, more quantitative description of time velocity waveforms and Doppler spectral content; and third, the estimation of absolute volume flow. Limitations of these methods for the abdominal signals obtained are discussed.

The interpretation of continuous wave ultrasonic Doppler blood velocity signals viewed as a problem in pattern recognition

The process of inferring the state of a patient's circulation from ultrasonic Doppler waveforms may be regarded as a problem in pattern recognition. In this article, each stage in the process, as it might be applied to the analysis of Doppler signals, is examined in turn and it is shown how an automatic on-line system for arterial assessment may one day be practical using such principles.

Analysis of femoral artery Doppler signals by LaPlace transform damping method.

The LaPlace transform damping (LTD) method of common femoral artery Doppler waveform analysis is a new method for assessing aortoiliac stenosis. A microcomputer was used to analyze the waveform to determine the value of the damping parameter, which is related to inflow stenosis. The study included 60 limbs with arterial disease and 20 limbs in normal control subjects. With a damping value of 0.60 used as the cutoff point between nonocclusive lesions and iliac stenoses of greater than 50% diameter reduction, we found a sensitivity of 100% and a specificity of 93% (overall accuracy 95%). Unlike Doppler waveform analysis by the pulsatility index method, the accuracy of the LTD method is not affected by occlusion of the superficial femoral artery. The Doppler signal processor and the computer currently used for the LTD analysis are simple to operate and fully suitable for routine use in a clinical vascular laboratory. Our experience indicates that the LTD method of waveform analysis provides the best noninvasive method for detection of significant inflow disease.

Analysis of femoral artery Doppler signals by LaPlace transform damping method

The LaPlace transform damping (LTD) method of common femoral artery Doppler waveform analysis is a new method for assessing aortoiliac stenosis. A microcomputer was used to analyze the waveform to determine the value of the damping parameter, which is related to inflow stenosis. The study included 60 limbs with arterial disease and 20 limbs in normal control subjects. With a damping value of 0.60 used as the cutoff point between nonocclusive lesions and iliac stenoses of greater than 50% diameter reduction, we found a sensitivity of 100% and a specificity of 93% (overall accuracy 95%). Unlike Doppler waveform analysis by the pulsatility index method, the accuracy of the LTD method is not affected by occlusion of the superficial femoral artery. The Doppler signal processor and the computer currently used for the LTD analysis are simple to operate and fully suitable for routine use in a clinical vascular laboratory. Our experience indicates that the LTD method of waveform analysis provides the best noninvasive method for detection of significant inflow disease.

Computerized evaluation of blood flow measurement indices using doppler ultrasound

The study involved computer-assisted analysis of Doppler blood flow signals from an in vitro experimental system utilizing a calibrated occlusive pulsatile pump, vinyl tubings of various dimensions, and human blood. The power spectra of these signals were obtained using the Fast Fourier Transform, and the peak and mean frequencies along with the first moments of the Fourier spectra around the zero-frequency axis were computed. These indices were evaluated using different flow rates and tubal dimensions. It was experimentally verified that the first moment provided a more linear measure of volume flow rate than that estimated by peak and mean velocities. Although the first moment cannot measure the absolute flow rate, it may serve as a better indicator of relative flow changes than the other two indices.

The quantitative analysis of Doppler signals for the measurements of blood flow in the fetus: J. M. Evans, P. N. Burns, J. M. Arnold, R. Skidmore, and P. N. T. Wells, Department of Medical Physics, Bristol General Hospital, Bristol, UK

The quantitative analysis of Doppler signals for the measurements of blood flow in the fetus: J. M. Evans, P. N. Burns, J. M. Arnold, R. Skidmore, and P. N. T. Wells, Department of Medical Physics, Bristol General Hospital, Bristol, UK

Vascular headache in pregnancy

The last two columns of Table I compare results from the Roche Fetasonde instrument adjusted optimally either directionally (seven records) or otherwise (nine records) with results from a fetal scalp clip electrocardiogram obtained simultaneously during labor. The only significant difference was in beat-to-beat variation, which was, on the average, nearly three times that recorded from the electrocardiogram. Signal loss with the Roche Fetasonde ultrasound equipment was a little greater during labor (mean, 7.2%) than antenatally (1.7% to 3.3%). It is also interesting to compare the correlations with simultaneous electrocardiogram (Hewlett-Packard) records in the present study in which the Roche Fetasonde 5 was used and those in a previous study in which the Hewlett-Packard instrument was used.’ With the Roche Fetasonde instrument the correlation coefficients were less (Table II). Hence, with the Hewlett-Packard electrocardiogram used as a standard, the reduced signal loss of the Roche Fetasonde 5 ultrasound instrument may have been achieved at the expense of some variability in results, even though the mean values during labor (last two columns of Table I) are not significantly different. The data also support the view that measurements of beat-to-beat variation by Doppler ultrasound are unlikely to be accurate, and there seems no point in using them as an index of fetal heart rate variation. Beat-to-beat variation is easily filtered out by averaging pulse intervals over 3.75 seconds; the remaining lower frequency but much larger component of heart rate variation provides a more reliable measure (Table I). In conclusion, these results demonstrate no advantage from directional analysis of fetal Doppler signals but a substantial reduction in signal loss when a broad transducer array with range-gating is used to enhance signal: noise ratio. It is evident that analyses of fetal heart rate records are partly dependent on the quality of ultrasound detector systems. It is, therefore, essential that manufacturers should specify the performance of detectors in more detail and that technical standards are agreed upon among users so that comparability is achieved between records obtained with different instruments.

Analysis of ultrasonic Doppler signals from malignant breast tumors

Analysis of ultrasonic Doppler signals from malignant breast tumors

Rotary spectrum analysis of sodar Doppler signals

Rotary spectrum analysis is a proven method for interpretation of geophysical data exhibiting inherent rotational characteristics. Computationally derived using a discrete Fourier transform, it shows the extent to which contributions to the total variance originate from clockwise or counterclockwise rotating components. The technique is well suited to the analysis of Doppler sodar signals which are sampled as the in (I) and quadrature (Q) phase components of a rotating phaser. The Penn State Doppler sodar system may be operated either in a “track” or I and Q mode. This paper demonstrates the advantages of I and Q sampling and rotary spectrum analysis for detailed interpretation of atmospheric wind and turbulence profiles. A comparison of Doppler‐derived and 123‐m tower measured winds will be presented.