Objective To predict and assess biomechanical responses and injury mechanisms of the thorax and abdomen for small-sized females in vehicle collisions. Methods The accurate geometric model of the thorax and abdomen was constructed based on CT images of Chinese 5th percentile female volunteers. A thoracic-abdominal finite element model of Chinese 5th percentile female with detailed anatomical structure was developed by using the corresponding software. The model was validated by reconstructing three groups of cadaver experiments (namely, test of blunt anteroposterior impact on the thorax, test of bar anteroposterior impact on the abdomen, test of blunt lateral impact on the chest and abdomen). Results The force-deformation curves and injury biomechanical responses of the organs from the simulations were consistent with the cadaver experiment results, which validated effectiveness of the model. Conclusions The model can be used for studying injury mechanisms of the thorax and abdomen for small-sized female, as well as developing small-sized occupant restraint systems and analyzing the forensic cases, which lays foundation for developing the whole body finite element model of Chinese 5th percentile female.

Objective: To explore the feasibility of real-time three-dimensional ultrasound Xplane imaging in quantifying left and right atrial diastolic maximal volume (LAVmax, RAVmax) and evaluating cardiac diastolic function in fetuses with cardiac disease in second and later trimesters. Methods: One hundred and forty-four fetuses with abnormal heart morphology at 16-34 weeks of gestational age were included and divided into 3 groups according to the influence of pathological changes on atrial volume: group A with symmetrical left and right atrial volume, group B with decreased left atrial volume and increased right atrial volume and group C with increased left atrial volume and decreased right atrial volume, and the fetus were also divided into 2 groups according to the law of fetal development: the middle pregnancy group (16-27^{+ 6} weeks) and the late pregnancy group (28-34^{+ 6} weeks). Using the " Xplane" mode of volume probe, the maximal atrial volume was calculated automatically by tracing method and three-path line method. The correlation between the two methods in quantitative LAVmax was validated by paired sample t test and Pearson correlation analysis. The correlation between LAVmax, RAVmax and gestational age were analyzed by curve fitting. The volumes of bilateral chambers and the average weekly growth rates of E peak, A peak and E/A value of mitral and tricuspid orifices were calculated and compared. Results: There was no significant statistical difference between the maximal volume of the left atrium obtained by the tracing method and the three-diameter line method (P>0.05), and there was high correlation between the two methods in the comparison of the maximal volume of the left atrium (r=0.90, 0.88, 0.85; all P<0.01). The data of group A, B and C showed that LAVmax and RAVmax could increase with the increase of gestational weeks in a certain period of abnormal state, and had a good correlation with them(LAVmax: r=0.78, 0.74, 0.78, all P<0.005; RAVmax: r=0.79, 0.77, 0.78, all P<0.005). The average weekly growth rate of RAVmax showed an advantage in group A, B and C. Especially in group C with reduced right atrium, the growth rate of right atrium was 8.15%, which was higher than that of group B with decreased left atrium by 5.06%. The weekly growth rates of E peak and E/A in tricuspid orifice were also higher than those in mitral orifice. The E peak and E/A values of tricuspid orifice in group C were 4.05% and 0.60%, respectively, higher than those in group B, which were 2.58% and 0.02%. Peak A showed an increase in growth rate in group B and group C with decreased atria, peak A values in group B and group C increased by 4.01% and 2.19%, respectively. Conclusions The right ventricular dominance of fetal heart can still be reflected in certain stages of disease, and the atrial active systolic may play a regulatory role in the filling of cardiac blood flow. Real-time three-dimensional ultrasound Xplane imaging could be used to quantify the atrial volume of fetuses with abnormal heart morphology in second and later trimesters and to preliminary assess atrial function combined with the changes of atrioventricular valve orifice hemodynamics. Real-time three-dimensional ultrasound Xplane imaging technology has obvious advantages of simple, safe, non-invasive, simultaneous and high repeatability in measuring fetal atrial volume.