(DCPD) Directional color power Doppler combines power (amplitude) of Doppler signal with directional (phase) information to encode direction and variations in blood flow. DCPD is used in analysis of blood flow to assess blood vessel or vascular function.

See also Color Power Doppler, Quadrature Detection, and Directional Indicators.

Ultrasound enhancement is the increase in reflection amplitude from objects that lie behind a weakly attenuating structure. Contrast agent particles enhance the reflectivity of blood.
The enhancement artifact may occur in structures below a cyst.

Enhancement artifacts occur if decreasing of the echo amplitude is not equal with penetration depth caused by inhomogeneous tissue layers and fluids like cysts or air-filled regions. The enhancement artifact appears as a hyperintense (hyperechoic) signal. The attenuation of the ultrasound wave in fluids is much lower as the attenuation in other tissues, therefore tissues distal to fluid are enhanced. Artificial enhancement may also be found distal to a homogeneous solid tumor surrounded by adipose tissue, due to the comparatively high attenuation in fat.

See also Boundary Layer, and Half-Value Layer.

(HVL) The attenuation of ultrasound waves in human tissue is characterized as the half value layer, or the half power distance. Half value layer means the distance the sound beam will travel in a tissue before its amplitude or energy is attenuated to half its original value. Air and lung tissue have extremely short half-power distances and represent severe obstacles to the transmission of acoustic energy.

(HPD) Harmonic power Doppler is currently one of the most sensitive techniques for detecting ultrasound contrast agents. HPD works by transmitting multiple pulses toward the object to be imaged and detecting the pulse-to-pulse changes in the received echo signals.
Second harmonic bandbass filtering is applied to the received signals to exploit the non-linear behavior of scattering from bubbles (clutter). Harmonic power Doppler operates best at high output levels because of increased contrast destruction, and pulse amplitudes close to the maximum allowed are used much of the time.
With a high mechanical index, non-linear propagation of the sound will cause significant harmonic components from tissue, and the contrast agent to tissue ratio will decrease.
Also called Harmonic Power Angio. See also Multiple Frame Trigger.