Assessment of fetal lung development by quantitative ultrasonic tissue characterization: a methodical study.

Abstract

This study was performed to evaluate the quantitative ultrasonic tissue characterization of the normal fetal lung development by using acoustic raw data captured after preprocessing. One hundred and sixty-two patients with completed gestational ages between 22 and 37 weeks were enrolled in this study. Longitudinal and transverse sections of the fetal thorax and upper abdomen were imaged. A region of interest of constant size was defined and the tissue-specific gray scale was determined by using an interactive software. A total of 162 patients met the inclusion criteria. The echogenicity of the fetal lung showed a particular changing pattern during pregnancy: the mean gray value of the fetal lung (MGV) is almost the same as the MGV of the fetal liver at 22 and 23 weeks, decreases between 22 and 31 weeks and increases between 31 and 37 weeks. The MGV of the fetal liver decreases significantly from 24 weeks to 31 weeks and increases significantly again toward 37 weeks. We stated that the MGV of the lung is smaller than the MGV of the liver during 31 weeks of gestation and the relation reverses in late gestation. At term, the MGV of the liver is greater than the MGV of the lung. The lung-to-liver ratio is <1 between 24 and 29 weeks and >1 between 30 and 35 weeks. The echogenicity of the fetal lung showed a particular changing pattern during pregnancy, which corresponds to morphologic changes of the fetal lung development.