Ultrasound. T1, T3, T4, T6 April 27, 2013. Review of how sound propagates. Longitudinal wave (consisting of compression and rarefaction areas) Speed of sound is dependent on the properties of the media it is traveling through
T1, T3, T4, T6
April 27, 2013
Utilizes sound waves of very high frequency way above the human hearing range
Human hearing range: Approximately 20 kHz
Similar to sonar or echolocation in bats
It is propagated from waves of compression and rarefaction, and requires a tissue to travel.
Bats transmit Ultrasound frequencies. They produce very short wavelength and high frequency pitches between 14,000 Hz and 100,000 Hz (Most are well above 20,000 Hz)
1) - Ultrasound waves are generated either by the larynx or nasal cavity
2) – Waves are sent out at regular intervals until the bat detects a moving object
3) – Ultrasound waves bounce off an object and the emitted pulse returns to the bat’s ears.
4) – The ears of the bat determine the location of the echo based on the subtle difference in time it takes for the sound to reach 1 ear and then the other
5) – The bat determines if the object is getting closer or farther away by the speed at which the echo returns
The machine measures the intensity of the waves by the number of echoes that are received in an area.
Random waves that are reflected back by various tissues and fluid are less intense so they do not compare to the intensity of the waves that display the fetus
Probe transmit ultrasound waves at frequencies of 1 – 5 MHz
Waves travel into the body until they hit a boundary between tissue and are reflected back
Multiple waves are sent out every second
The reflected waves that bounce back are received by the probe and transmitted to the machine