Biomedical subjects

P Zuech

Publications and source records attributed to P Zuech.

3 recordsLinked to original sources

PubMedDate not supplied

An in vitro model and its application for the study of carotid Doppler spectral broadening.

A new in vitro model has been developed for studying the changes in the ultrasound Doppler spectrum that occur in the region of a stenosis. Pulsatile flow in rigid acrylic tubes was produced by means of a modified hemodialysis pump. The Doppler spectral waveforms were measured using a continuous wave Doppler system, a probe of a known field pattern, a real-time high resolution frequency analyzer, and a video display and recording system. The flow velocity waveforms were found to be nearly identical to those seen in the human carotid. Measurements were made to determine the critical stenosis and the results are similar to those reported from in vivo studies. In a preliminary study, the extent of spectral broadening was found to be dependent on the recording site in relation to the stenosis, the severity of the stenosis, and the flow rate. Using qualitative methods it was not possible to determine either the influence of the shape of the stenosis or the phase of the cardiac cycle on spectral broadening.

Carotid Arteries↗

PubMedDate not supplied

In vitro comparison of alternative methods for quantifying the severity of Doppler spectral broadening for the diagnosis of carotid arterial occlusive disease.

Quantitative analysis of continuous wave Doppler recordings is of clinical value in the noninvasive diagnosis of carotid arterial disease. Peak frequency measurements are useful and accurately detect severe stenoses but do not reliably diagnose minor or moderate stenoses because the measurement is dependent upon the probe to vessel angle, which cannot be measured accurately. Recent investigations have focused on efforts to overcome this limitation by quantifying the degree of spectral broadening that occurs as the result of flow disturbances downstream from a stenosis. In this study, an in vitro model was used to determine the optimum method for quantifying the instantaneous Doppler spectrum. The model generates blood flow velocity waveforms that are virtually identical to those found in the human internal carotid artery. Doppler recordings were made from normal tubes and distal to stenoses (39-87% cross-sectional area reduction). The spectra were quantified by the following angle-independent measurements: spectral broadening index and three standard statistical shape descriptors, namely the coefficients of variation, skewedness and kurtosis. Using this model, the results demonstrate an excellent relationship between the severity of the stenosis and each of spectral broadening index (r = 0.99), coefficient of variation (r = 0.96), and coefficient of skewedness (r = 0.99). The calculation of each of the measurements can be implemented quite easily, and a prospective trial is warranted to evaluate their clinical diagnostic accuracy.

Arterial Occlusive Diseases↗

PubMedDate not supplied

[What's bugging him?].

The purpose of this study is to report the case of a 34 year old patient, from Zaïre for whom a wrong diagnosis could have been fatal. Recent events in his affective and professional life, associated with typical symptoms, suggested a major depression. However after two months of being admitted a psychiatric ward, the resistance to treatment together with some biological data suggested further investigations. They revealed a subacuse meningo-encephalitis of parasitological etiology. The psychiatric aspects of trypanosomiasis commonly known by clinicians in Africa justifies, in patients from that continent, a systematic test for trypanosomiasis.

Acute Disease↗