A continuous wave primarily has three parameters. They consist ofamplitude, frequency and the initial phase. The pulsed waveparameters include pulse duration, pulse repetition period (PRP),pulse repetition frequency (PRF), spatial pulse length and dutyfactor. Despite the two waves having individual parameters, they alsoshare a few of them such as frequency, period, propagation speed andthe wavelength.
In the pulsed wave, pulse repetition frequency is the exact number ofpulses that happen in one second. It’s dependent on the pulserepetition period by being its reciprocal. That is, PRF decreases asthe imaging depth increases. However, it’s entirely unrelated tothe transducer frequency, and the depth of view determines it. PRF ismeasured in Hertz per second (Hz/sec) and the sonographer can changeit during alteration of the imaging depth. In clinical imaging, itranges from 1,000 to 10,000 Hz.
In the continuous wave, the frequency is measured in Hertz, and itreciprocates both the period (time taken to complete a cycle) and thewavelength. It increases while both the time and wavelength decreaseand vice versa. It is determined by the sound source too as in pulsewave. The rate varies in across different sounds such as inultrasound it’s above 20000Hz, infrasound is below 20Hz, audiblesound 20-20000Hz, and in the diagnostic ultrasound, it ranges from100Hz to 2000Hz.
The parameters are used during the analysis of blood by the Dopplertransducer. The pulsed wave ultrasound is preferred to thecontinuous-wave because it allows the depth of the flow site to bemeasured while the latter is unable to determine the precise locationof velocities in the beam and it can’t produce clear color flowimages. The parameters are also essential in cardiology as their datais used in detecting abnormalities related to the cardiac system(Otto, 2013). They are also indispensable in urology as they aidmeasure the rate of blood flow through the kidney, and in thedetection of kidney stone and prostate cancer. Finally, they areuseful in obstetrics and gynecology as they are crucial for themonitoring of the fetus development and detection of tumors of thebreast and ovary (Bamber et.al., 2013).
Bamber, J., Cosgrove, D., Dietrich, C. F., Fromageau, J., Bojunga,J., Calliada, F., & Fink, M. (2013). EFSUMB guidelines andrecommendations on the clinical use of ultrasound elastography. Part1: Basic principles and technology. Ultraschall in derMedizin-European Journal of Ultrasound, 34(02), 169-184.
Otto, C. M. (2013). Textbook of clinical echocardiography.Elsevier Health Sciences.