A combined ultrasonic linear array scanner and pulsed Doppler velocimeter for the estimation of blood flow in the foetus and adult abdomen--I: Technical aspects.

A method is proposed for estimating the volume blood flow of deep lying vessels in the foetus and in adult portal vein and renal vessels. The equipment combines a 3.5 MHz linear array scanner with a 2 or 4 MHz pulsed Doppler. The pulsed Doppler tranducer is connected to the linear array by two movable arms. A real time spectrum analyser is used to process the Doppler signals. A water bath was used to perform an in vitro calibration of the complete system and to adjust the registration of the Doppler sample volume with the echo picture. Several possible inaccuracies in vessel diameter measurement are discussed and the mean of several caliper measurements described by Eik-Ness (1982) is used. Time Motion is thought to be the better method but is more complicated in practice.

A combined ultrasonic linear array scanner and pulsed Doppler velocimeter for the estimation of blood flow in the foetus and adult abdomen--II: Clinical evaluation.

A combined pulsed Doppler and linear array scanner is used to measure volume blood flow in 75 aortas and 45 umbilical veins of foetuses in the 3rd trimester. The mean aortic flow was 277 ml/min/kg and the mean umbilical venous flow was 122 ml/min/kg. Mean flow in the portal veins of normal subjects was found to be between 0.6 and 2.0 l/min. Clear signals were obtained from the adult kidney but no volume flow calculation has yet been attempted. The use of a spectrum analyser is considered fundamental to the accurate interpretation and processing of the Doppler signals. Medical and electronic artefacts are described which would not be detected without the use of an analyser.

New doppler technique for assessing uteroplacental blood flow.

Gated, pulsed, doppler ultrasound was used to study blood flow velocity profiles in the uterine vessels (arcuate arteries) during the second and third trimesters of pregnancy. A frequency index profile nomogram was constructed from 30 normal pregnancies; this demonstrated high diastolic velocity and low pulsatility. Among 31 pregnancies with complications 14 showed waveform changes suggesting raised vascular resistance; these pregnancies were complicated with a high frequency of proteinuric hypertension, poor fetal growth, and fetal hypoxia. This non-invasive technique may give early warning of impaired uteroplacental perfusion and can be used to evaluate methods of improving uterine blood flow.

[Methods for discriminating flow direction with continuous wave Doppler equipment]. / Methoden der Richtungstrennung bei Dauerschall-Dopplergeräten.

The application of ultrasound Doppler units for the localization of incompetent venous valves, the examination of extracranial vessels, and the evaluation of the hemodynamic effect of certain cardiac dysfunctions requires directional models with the possibility of recording Doppler wave forms. Various techniques are used to determine flow direction all of them presenting specific advantages and disadvantages in practical use. After briefly explaining the basic Doppler technique, the three most commonly used methods, the two-channel filter technique, the McLeod system, and the outphaser system, are described. The characteristics of the various signal processing techniques are discussed, particularly in the case of complex hemodynamic conditions.

Intraoperative Doppler coronary artery finder.

Time-consuming difficulty is occasionally encountered in finding coronary arteries or previously placed vascular grafts during coronary revascularization procedures. A catheter-tipped, continuous-wave Doppler ultrasonic probe with simple audio output has been shown to be capable of expediting the search for these vessels.