F.M. Greene

Flow velocity patterns in the carotid bifurcations of young, presumed normal subjects

Spectral analysis of pulsed Doppler velocity waveforms has been found useful as a diagnostic technique in the assessment of carotid artery disease. While spectral broadening of the velocity waveform obtained at center stream sites is usually associated with arterial disease, the present study describes spectral patterns resulting from disturbed blood flow in the proximal branches of the carotid bifurcation in young, presumed normal human subjects. In those studied, spectral patterns in the bifurcation region exhibit characteristics similar to those occurring in zones of flow separation in model studies under conditions of steady flow. It is important to distinguish the spectral patterns due to arterial disease from those occurring in the normal bifurcation. This paper describes the types of flow disturbances noted in presumed normal arteries and points out the need to understand the flow velocity patterns that may be found at specific anatomical sites across the carotid bifurcation.

Ultrasonic doppler diagnostic system using pattern recognition

A frequency-analyzed signal from a pulsed Doppler ultrasound examination is processed in a dedicated computer using statistical pattern recognition to assess the presence and extent of arterial disease. The Doppler blood flow signal is derived from a suitable utlrasound scanner, is frequency analyzed with a real-time, fast Fourier Transformer spectrum analyzer, and is processed by the computer to achieve a diagnosis of the degree of stenosis of the carotid artery through pattern recognition between the Doppler signal and a database of known preclassified spectra. The diagnosis ordinarily follows a hierarchical decision making format to objectively classify the condition of the patient.

Computer based pattern recognition of carotid arterial disease using pulsed Doppler ultrasound

A minicomputer based system has been developed for studying carotid artery blood flow data obtained for a combined B-mode, pulsed Doppler ultrasound scanner. The goals of this work are to devise and improve techniques for estimating the extent of atherosclerosis at the carotid artery bifurcation. Features are automatically extracted from spectrum analyzed Doppler blood flow data. Five statistical pattern recognition algorithms are compared, with cross validation being used to improve the estimate of classification accuracy. A data collection protocol has been devised in which four sites are studied along each carotid arterial system. Classification of unknowns is done using a hierarchy of three decisions.

Computer based pattern recognition of carotid artery doppler signals for disease classification: prospective validation

A computer based pattern recognition method has been developed to classify the percent diameter reduction in nonoccluded internal carotid arteries. Using a combined B-mode/pulsed Doppler unit, the system utilizes spectral waveforms obtained from the low common and proximal internal carotid artery locations. The ECG-R wave is used as a time reference to synchronize the averaging of Doppler spectra from 20 heart cycles. An averaged waveform is generated and represents the spectral data from which features are extracted for analysis. A stepwise selection algorithm identifies a feature subset for partitioning the entire range of disease into two states, less than and greater than a decision point. Three such partitions are made, leading to the following categories: Normal, 1-20, 21-50 and 51-99% dia. reduction. A classifier was trained, tested prospectively against unknown data and the results compared to angiography. Of the 170 vessels tested, 141 (82%) were classified in the same category by angiography and the computer system. Agreement for each category was 93% (27/29) for the normals, 81.5% (44/54) for the 1-20% lesions, 78% (29/37) for the 21-50% lesions and 82% (41/50) for the 51-99% lesions. The computer method and angiography differed by more than one category in only one of the 170 tests. The level of agreement corrected for chance (Kappa +/- SE(K] was 0.769 +/- 0.039. Future efforts will be directed toward dividing classification of disease further (especially in the 51-99% category), developing a dedicated microprocessor for on-line analysis of the signals and using the system for prospective epidemiological studies of various populations.

Computer based classification of carotid arterial disease: a prospective assessment.

A minicomputer based pattern recognition method has been used to prospectively classify the category of disease involvement of 105 carotid arteries. The system utilized spectral patterns obtained from a combined B-mode/pulsed Doppler unit. All decisions are based upon comparison of an unknown, averaged waveform with a series of vessels with known severity of disease. The variability in the computer decision as compared to arteriography is discussed.

A method for utilizing diploid/dominance in genetic search

A method is proposed for implementing diploid/dominance in genetic search. Both diploid strings, in a single gene example are evaluated to produce two intermediate phenotypes which then determine dominance. Experimental results indicate that changing global optima are accurately identified and followed. The method is problem independent and can be readily extended to a polyploid chromosome structure.<<ETX>>

Effect of carbon dioxide on flow patterns in normal extracranial arteries

Abstract To evaluate the velocity pattern changes in the extracranial carotid arteries, five normal subjects were studied with a 5-MHz pulse Doppler device combined with spectral analysis prior to and during breathing 6.8% carbon dioxide. Changes in flow were quantified by features derived from the velocity waveform of the common, internal and external carotid arteries. An increase in velocities during diastole correlated well with the expected increase in total blood flow induced by breathing 6.8% carbon dioxide. Increases in spectral width reflected the development of flow disturbances not apparent under basal conditions. These studies suggest that marked increases in flow produced by intracranial vasodilatation can dramatically alter the velocity patterns normally observed.

Computer aided pattern recognition and 3-D reconstruction of carotid stenosis

An inexpensive computer system for signal analysis of ultrasonic Doppler data, pattern recognition, and three-dimensional reconstruction of ultrasonic B-mode images is described. The hardware architecture consists of an IBM PC/AT, a TMS 32025 co-processor, and a DMA interface. Display is output using standard EGA hardware. Test results are presented and discussed.<<ETX>>

Pattern recognition of carotid artery diseases using pulsed Doppler ultrasound

Computer pattern recognition of carotid artery atherosclerosis has been implemented in dedicated systems. Accuracy is equivalent to that of an expert sonographer and is repeatable for different sonographers. The system uses algorithms which were systematically trained from a database of 318 cases having arteriographic confirmation, plus 88 asymptomatic normals. A software language was implemented to aid in maintaining the system.<<ETX>>