Umbilical arterial and venous doppler waveforms as demonstrated by Ashitaka, Murachi and Takemura in 1968.
Source: Yasuharu Nimura "Introduction of the Ultrasonic Doppler Technique in Medicine: A historical perspctive". J Med Ultrasound 1988, 6:5-13.
Read also: A brief history of the pioneering work in Doppler applications in Japan.
Ashitaka Y, Murachi K, Takemura H. et al. Analysis of the motion of the heart valve with the fetal electrocardiogram, phonocardiogram and doppler signals. Proceedings of the 14th Scientific Meeting of the Japan Society of Ultrasonics in Medicine. 1968: 29-30. (in Japanese).
Back to History of Ultrasound in Obstetrics and Gynecology.