(CPS) Contrast pulse sequencing is a technique to exploit contrast agent properties with series of three pulses that differ in phase and amplitude. CPS allows bubble specific imaging with non-linear fundamental and higher order harmonics, low MI, and extremely high microbubble-to-tissue background ratio.

See also Ultrasound Contrast Agent Safety.

Doppler ultrasound is a medical imaging technique for calculating the relative velocity between two points by measuring the frequency shift of a sound wave transmitted from one point to the other, based on the Doppler effect. Continuous or pulsed Doppler is frequently used to examine cardiovascular blood flow. The combination of routine 2D-mode and Doppler ultrasound allows a complete evaluation of the heart's anatomy and function (including the fetal heart). See also Doppler Fluximetry in Pregnancy.
Doppler ultrasound depends on the fact that if a moving object reflects the ultrasound waves, the echo frequencies are changed. A higher frequency is created if the object is moving toward the probe//transducer and a lower frequency if it is moving away from it. How much the frequency is changed depends upon how fast the object is moving. Doppler ultrasound shows the different rates of blood flow in different colors on a monitor in real time.
The major Doppler parameters are the peak systolic velocity and the end-diastolic velocity. The peak systolic velocity ratio compensates the variability between different patients and instrumentations.

Different Doppler and duplex techniques:

Dual frequency phased array transducers allow performing third or fourth harmonic imaging. This array design contains two different types of elements arranged in an interleaved pattern (odd and even elements). The elements can work individually and at a distinct frequency enabling separate transmission and receiving modes.

From Philips Medical Systems;
Introduced in June 2005, 'one of the less expensive and more dedicated' ultrasound systems.

(Hz) The standard SI unit of frequency.
Definition: The number of repetitions of a periodic process per unit time. It is equal to the old unit cycles or oscillations each second of a simple harmonic motion. The unit is named for the German physicist Heinrich Rudolf Hertz.
Larger units are
kilohertz (kHz) = 1 000 Hz
megahertz (MHz) = 1 000 kHz
gigahertz (GHz) = 1 000 MHz