Application of spatio-temporal image correlation combined with high-difinition flow in demonstration of fetal azygos vein during the second gestation

Objective To evaluate the feasibility of demonstrating the fetal azygos vein by spatio-temporal image correlation(STIC) combined with high-difinition flow(HD) imaging during the second gestation. Methods Two hundred fetuses between March 2013 to November 2013 were divided into 2 groups. In study group, STIC and HD were applied to demonstrate the azygos vein on the fetal thoracoabdominal para-midsagittal view, the relationship between the azygos vein and thoracic aorta, the shape, location and modality of archof azygos vein which joins the superior vena cava were observed after post processing.And two-dimensional ultrasound and color Doppler flow imaging(CDFI) was applyed in the control droup. Results 96/100 of the azygos vein was successfully demonstrated in the study group with the rate of 96%,while 85/100 was successfully demonstrated in the control group with the rate of 85%. According to the relationship of the azygos vein with the spine,the proportion of the right type,middle type and left type of the azygos vein was 26.0%,33.9%,40.1%. The azygos vein parallels with the thoracic aorta upside to the level of superior vena cava,and bends forward and joins the superior vena cava. In one case with hepatic segment of inferior vena cava interruption, wthe azygos vein was dilated with similar diameter to the thoracic aorta. Conclusion It is feasible to demonstrate the azygos vein by STIC combined with HD. The diameter, shape, location and manner of azygos vein can be observed.It can hint the diagnosis of disease that results in expansion of azygos vein. It is better than two-dimensional ultrasound combined.