Doppler probe

Doppler probe [Christian J. Doppler] , a handheld diagnostic device that emits ultrasonic waves into the body. Reflection of the waves by a moving structure causes a change in their frequency. The Doppler probe has been used as a diagnostic tool since 1960 to study changes in blood flow in arteries and veins.

Esophageal Doppler probe (Carlson and AACN, 2008)