The Evaluation Of Dopper Ultrasound In Measuring The Aortic Isthmus Of The Fetuses

Objective:By using the color Doppler ultrasound to measure Doppler indexes of the aortic isthmus, the umbilical artery and the middle cerebral artery, the aim of this paper is to get the normal reference ranges of the Doppler indexes of the aortic isthmus and further to assess all indexes’variation in intrauterine hypoxia and discuss the corresponding clinical value.Method:We performed our study on381normal fetuses with gestational age ranging from21to39+6weeks,19cases of FGR and15cases of Pre-eclampsia with gestational age ranging from28+1to39+5weeks. Apart from measuring the growth index of the fetuses, the Doppler color ultrasound was also used to measure the AoI, UA and MCA Doppler indexes PSV, ESRV, PSV/ESRV, UA-PI, and MCA-PI. Correlation analysis was first applied to discuss the correlation of the AoI Doppler indexes (PSV, ESRV, PSV/ESRV), the gestational age (GA) and the growth indexes (HC/AC/FL). Then, regress the logarithm form of PSV, ESRV, PSV/ESRV on GA to do goodness of fit test and linear prediction, respectively. To assess the difference between the normal fetuses and the fetuses with FGR and Pre-eclampsia on AoI, UA and MCA Doppler indexes, respectively, we first used the two-sample T-test and then applied the analysis of variance (ANOVA), in which we considered the log of each Doppler index as the dependent variable, the indicator based on FGR and pre-eclampsia as a fixed factor, and the log of gestational age as a covariate.Consequence:Correlation analysis based on AoI Doppler indexes of the normal fetus and the gestation ages showed that the indexes are closely related to the gestational ages. The correlation between the log value of AoI Doppler indexes and the gestational ages was also analyzed, respectively, and it demonstrated that PSV, ESRV, and PSV/ESRV are closely related to the gestational ages. Further, based on the sign of correlation coefficients, we can see that both PSV and ESRV grow with the increase of the gestational ages while PSV/ESRV decreases. To find the best regression model in terms of prediction, we regressed the log value of each AoI Doppler index on the gestational ages (GA) under the linear model framework. Hence, the corresponding prediction models are log(PSV(cm/s))=2.86+0.52*log(GA)、 log(ESRV(cm/s))=-0.98+1.23*log(GA). log(PSV/ESRV)=3.84*log(GA). The graphical residual analysis showed the homogeneity of variance and normal distributed property. And further, the goodness of fit test demonstrated that the prediction linear models are appropriate for the data (P<0.01). Consequently, based on the theory of normal distribution, the normal reference ranges were established with the calculation of antilog. For comparison on normal and abnormal fetuses, the two-sample T-test showed that there is no difference in terms of PSV before adjusting the gestational ages, while there is significant difference in terms of both ESRV and PSV/ESRV (P<0.01). Moreover, the analysis of variance showed that there is significant difference (P<0.01) in terms of both ESRV and PSV/ESRV between normal and abnormal fetuses after adjusting the gestational ages. PSV/ESRV of the abnormal ones is lower than that of the normal ones, while ESRV is higher in abnormal ones. For comparison on normal and abnormal fetuses, the two-sample T-test showed that there is no difference in terms of MCA-PI before adjusting the gestational ages, while there is significant difference in terms of UA-PI (P<0.01). Moreover, the analysis of variance showed that there is no significant difference in terms of MCA-PI between normal and abnormal fetuses after adjusting the gestational ages, while there is significant difference in terms of UA-PI (P<0.01) and UA-PI of the abnormal ones is higher than that of the normal ones.Conclusion:The normal reference ranges of the Aol Doppler Indexes have been preliminarily established based on local fetuses data. The AoI Doppler Indexes (ESRV and PSV/ESRV) may significantly change in cases of FGR and Pre-eclampsia. And they may vary in the case of intrauterine hypoxia. Moreover, UA and AoI Doppler Indexes may change earlier than the MCA Doppler index.