INTRA-UTERINE GROWTH RETARDATION VASCULAR MODEL WITH A SOFTWARE SYSTEM FOR ULTRASOUND QUANTITATIVE AND QUALITATIVE ANALYSIS

Abstract

The use of sonographic examina tion and doppler ultrasound has made it possible to achieve reliable diagnosis of fetal growth retardation. Since the fetal circulation is relatively inaccessible to study, an electrical analogue computer model is developed. The purpose of this model is to investigate the factors that determine the velocity waveform shape in normal and abnormal pregnancy. Thus help in diagnosing the intra-uterine growth retardation and reaching a more solid decision about the fetal physical state. The model, which is based on the transmission line theory, simulates the circulation in the umbilical arteries and vein. The model is used to predict the incident and reflected components of both the flow and pressure waveforms. It also predicts the pulsatile changes of the radius and the velocity waveform. From the velocity waveform the systolic to diastolic· ratio and the pulsatility index are calculated. Also, a new biophysical parameter which is the pulsatile component of the reflected flow waveform is calculated and its clinical value is demonstrated. The param eters of the model were then varied either independently or in combination under realistic ranges. Thus, reproducing changes in the waveform which are associated with pregnancy induced hypertension, fetal heart malfunction and other anatomical changes that may lead to intra-uterine growth retardation.