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Biomedical subjects

N F Güler

Publications and source records attributed to N F Güler.

8 recordsLinked to original sources
PubMed2001

Software development for medical instrumentation.

Computer-assisted medical instrumentation has recently become more common. For accuracy and precision, the computer and interfacing circuit with the associated digital signal processing algorithm can be used for the evaluation of biological signal. The measurement system based on this structure has a very high degree of efficiency and flexibility because different algorithms can be used. In addition, the system can employ some newly developed software packages. This paper will submit a procedure for computer-assisted medical instrumentation, and also will show a specific application on blood flow.

Blood Circulation↗
PubMed1998

The derivation of theoretical ultrasonic Doppler blood flow spectrum.

This paper deals with theoretical aspects of blood flow and the ultrasonic Doppler spectrum. Blood flow in the vessel can be considered as a pipe flow with a circular cross-section. Blood flow is, in general, complex and pulsatile. Navier-Stokes and the continuity equations are the governing equations for the blood flow, and the Navier's equations for the blood vessel. If the flow is pulsatile with a large Womersely number, the velocity profile becomes blunt due to the inertia forces. Since the ultrasonic Doppler flowmeter detects the velocities of blood cells across the vessel, Doppler power spectrum is dependent on the velocity profile. If the velocity profile is blunt, the Doppler power spectrum will be narrow banded. If the flow is sinusoidal, the Womersely number is only a parameter describing the pulsatility. Blood flow waveforms, however, differ from the sinusoidal wave. They consist of a steady flow component and many harmonics with amplitudes and phases. In this study, the influence of the harmonic contents and the Womersely number on velocity profiles and the Doppler power spectrum are examined.

Algorithms↗
PubMed1996

Order determination in autoregressive modeling of diastolic heart sounds.

Previous studies demonstrated that spectral analysis of diastolic heart sounds may provide valuable information for the detection of coronary artery disease. Although parametric modeling methods were successfully used to achieve this goal, and showed considerable performance, the accuracy and precision of the analysis is strongly dependent on the model order selected. In order to investigate the effects of model order selection on the analysis, diastolic heart sound recorded from both normal and diseased patients were analyzed using the AR modeling, which is computationally the most efficient parametric spectral analysis method. The model order were determined by using four different model order selection criteria. The results showed that the four criteria yielded different order for the same data set. On the other hand, different criteria showed different performance in different measurement conditions. Effect of arbitrary order selection was also discussed. As a result, an optimal AR model order that may be used for every case was determined.

Computer Simulation↗
PubMed1996

Application of autoregressive and Fast Fourier Transform spectral analysis to tricuspid and mitral valve stenosis.

Tricuspid and mitral valve flow area was determined from an apical four-chamber view. Doppler signals were recorded from normal subjects and patients with tricuspid and mitral valve stenosis by using a pulsed Doppler unit. The location of sample volume was chosen at the ventricular side of the valve orifice and within the right ventricular tract. This was done with the aid of an integrated cardiac imaging facility. The analog signal at the output of the Doppler unit was sampled and digitized using an analog/digital interface board and transferred to a personal computer. The data were then analyzed using the Fast Fourier Transform (FTT) and autoregressive (AR) modeling methods of spectral analysis and all the sonograms were obtained. Statistical comparison between the FFT and AR methods was made. The results show that the AR method offers a superior performance over the FFT method as regards the assessment of tricuspid and mitral valve stenosis.

Adult↗
PubMed1995

A time domain mean frequency estimation algorithm of two-dimensional real-time Doppler imaging system.

A time domain mean frequency estimator is proposed for use in the two-dimensional real-time Doppler ultrasound blood flow imaging system. Since the frequency domain techniques require a long observation period to resolve the frequency content of the Doppler signal spectrum, it is unsuitable for real-time two-dimensional applications. Performance characteristics of the Doppler mean frequency estimator are obtained using a computer simulation, which models the Doppler signal and the signal processing network.

Algorithms↗
PubMed1995

Comparison of FFT- and AR-based sonogram outputs of 20 MHz pulsed Doppler data in real time.

Real time sonogram outputs of autoregressive (AR) and Fast Fourier Transform (FFT) spectral analysis of 20 MHz pulsed ultrasonic Doppler blood flowmeter are presented. Data obtained from coronary, renal, iliac, digital and mesenteric arteries were processed using AR- and FFT-based spectral analysis techniques and interpretable sonograms were constructed. In comparison with the FFT-based sonogram outputs. AR-based sonogram outputs for 20 MHz pulsed Doppler data provide better results. Hence, the AR modeling is strongly recommended for small vessels with diameters between 1 and 2 mm.

Adult↗
PubMed1995

Autoregressive-based sonogram outputs of 20 MHz pulsed Doppler data.

The sonogram outputs of autoregressive (AR) based spectral analysis of a 20 MHz pulsed ultrasonic Doppler blood flowmeter are presented. The data obtained from coronary and iliac arteries were processed using AR-based spectral analysis technique, and then the interpretable sonograms by the surgeons were constructed. When the sonogram outputs were compared to other sonograms which were analysed using the other techniques such as fast Fourier transform (FFT), it was observed that AR-based sonograms for 20 MHz pulsed Doppler data have provided better results. Therefore, the technique is strongly recommended in the examining of small vessels which are 1 to 2 mm in diameter.

Adult↗