Chest with Heartbeat (IMAGE) University of California - San Francisco Caption This ultrasound image shows a fetal mouse heart accompanied by an M‑mode Doppler reading of the heart rate. Credit UCSF Usage Restrictions Credit UCSF License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.