Ultrasound core laboratory for the Household Air Pollution Intervention Network trial: standardized training and image management for field studies using portable ultrasound in fet... by Dávila-Román, VG, Toenjes, AK, Meyers, RM, Lenzen, PM, Simkovich, SM, Herrera, P, Fung, E, Papageorghiou, AT, Craik, R, McCracken, JP, Thompson, LM, Balakrishnan, K, Rosa, G, Peel, J, Clasen, TF, Hossen, S, Checkley, W, Fuentes, LDL