Pulse Wave Doppler (PWD)
Pulse Wave Doppler is an imaging technique based on the ultrasound imaging principle. Ultrasound images of blood flow, either by Color Flow, Power Doppler, Continuous Wave, or Pulse Wave Doppler all essentially give the movement of the blood. Using any of the methods details about the heart circulation and blood can be found. In the technique of Pulse Wave Doppler (PWD) a series of electrical pulses are transmitted to visualize the movement of blood.
The electrical pulses sent give the echoes; depending upon the echoes the blood flow is calculated. By the Doppler Effect it can be clearly differentiated among the blood vessels and the body tissues. As the echoes from the stationary type body tissues are constant and do not change from pulse to pulse while echoes from the moving objects like blood changes from time to time with every pulse. These differences in the flow can be directly measured by the time difference or in terms of the phase difference from which the Doppler Frequency is determined.
In Pulse Wave Doppler imaging the electrical signals are sent in the form of pulses. The transmission of the pulsated signal is produced by the oscillators, which changes its voltage according to the resonance frequency. Short duration pulses of the ultrasound frequency are sent with a specific frequency, which is known as pulse repetition frequency (PRF). In the duration of the pulse transmission echoes continuously returns to the receiving transducer, but all the receiving signals are not viewed. The receiving transducer has its fixed frequency to open the gate for receiving the signals. The shift in the frequency from the pulse transmission is to allow the estimation of the Doppler Frequency Shift.
Pulse Wave Doppler is a famous technique used for imaging the blood flow by the electrical pulse methods and the technique has its own instruments, which are used to measure the blood flow.






