Measurements on intensity output of Doppler ultrasound devices used for fetal, neonatal and infant application : H. Rabea, B. Grohsb, R.M. Schmidtb, R. Schlohc, W. Holzgrevec and G. Jorcha. aDepartment of Paediatrics, University Hospital, Münster, F.R.G., bFraunhofer-Institut, Saarbrücken, F.R.G. and cDepartment of Obstetrics and Gynaecology, University Hospital, Münster, F.R.G.