A fetal doppler is a non-invasive diagnostic instrument that uses sound waves to send information back to the user. There are two types of fetal dopplers available: fetal heart doppler and doppler ultrasound. The fetal heart doppler allows a physician to monitor the unborn child's heartbeat through the mother's stomach. The doppler ultrasound is used similar to a regular ultrasound, although the purpose is to view blood flow through the fetus.
The process on which a fetal doppler is based is called the Doppler Effect. This was discovered by Christian Doppler, an Austrian physicist and mathematician.
The fetal heart doppler contains a transducer that contains piezoelectric crystals. These crystals send short sound pulses toward the heart of the fetus. Once a pulse is sent, the transducer pauses in order to listen for an echo. Once an echo is heard, the transducer determines the depth and direction from which the sound wave echoed. This information is then processed into the sound that is projected to the physician and heard as a heartbeat.
The same principle is used with doppler ultrasound. The device contains a transducer that holds several piezoelectric crystals. These crystals emit sound waves through the mother's body toward the fetus. When a sound wave hits a solid material such as blood cells, the wave is reflected back toward the transducer. The echo that is heard by the transducer is converted into information, such as the depth and direction. Once the transducer has converted this information, the device produces the information as an image or as a sound pattern.
The sound pattern of blood flow is heard as a "swooshing" sound, and the visual results show the image of blood flowing through the veins and arteries.
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