ShearWave elastography of fetal lungs in pregnant baboons

Purpose: The purpose of this study was to evaluate the feasibility and reproducibility of transabdominal ShearWave elastography of fetal lungs in pregnant baboons.

Materials and methods: During a 9-month period (03/2013-12/2013), two operators prospectively performed ultrasound examinations of fetal lung in pregnant baboons in a primate research center. Evaluation of fetal lungs was first performed in B mode. The ShearWave elastography mode was then activated. Three elasticity measurements were performed by each operator for each lung. Each time, the operator recorded whether the lung was distal or proximal regarding the distance to the probe. Intra- and interobserver reproducibility was assessed using intra-class correlation coefficients (ICC).

Results: Twenty-one pregnant baboons were included and ultrasound examinations were performed between 1 and 3 times on each baboon. Measurements were feasible by both operators in 100% of the cases. Intra-observer ICC for the single values of proximal and distal lungs were 0.336 (95% CI: 0.191-0.484) and 0.433 (95% CI: 0.292-0.570), respectively. Intra-observer ICC for the average values of proximal and distal lungs were 0.603 (95% CI: 0.415-0.738) and 0.697 (95% CI: 0.553-0.799), respectively. Inter-observer ICC for the single values of proximal and distal lungs were 0.654 (95% CI: 0.422-0.806) and 0.421 (95% CI: 0.113-0.654), respectively. Inter-observer ICC for the average values of proximal and distal lungs were 0.791 (95% CI: 0.593-0.893) and 0.592 (95% CI: 0.203-0.791), respectively.

Conclusion: Transabdominal ShearWave elastography of fetal lungs in pregnant baboons is feasible. However, intra- and inter-operator reproducibility is acceptable when the mean of three measurements is used. Further studies are thus needed before an objective study of lung maturity with ShearWave elastography can be carried out.