RIU 324 Lecture Notes - Lecture 15: Rayleigh Scattering, Blood Vessel, Sonographer
29 Mar 2020
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Objectives: what is the doppler shift? the doppler shift is the difference between the received and transmitted frequencies. (reflected- transmitted) Relative motion between the sound sourced and the receiver causes a change in frequency. 2,000,000 to 10,000,000 hz (2 to 10 mhz) are used in clinical trials. When blood cells move toward the transducer, the doppler shift is positive, the reflected is higher than the transmitted. When blood cells move away from the transducer, the doppler shift is negative, the reflected frequency is lower than the transmitted: be able to use the doppler equation to calculate doppler shift or velocity of blood. The percentage of true velocity that is measured depends on the cos of the angle between the sound beam and the direction of motion. Since the cos of 60 is . 5, the measured velocity at. 60 degree is one half the actual velocity.
