Correlation is a mathematical procedure, used in ultrasound to quantify the similarity between two signals. Cross correlation of successive ultrasound echoes can be used to quantify movement of tissue, including blood.

The autocorrelation is a mathematical procedure used to quantify periodicity in a Doppler signal and forms the basis of most color Doppler velocity estimators. The autocorrelation multiplies waveforms by successively time-shifted sections of itself.

Ultrasound at the microbubble resonance frequency can cause bubble rupture at high acoustic power (mechanical index (MI) greater than 0.5). The result is a transient high-amplitude, broadband signal containing all frequencies, not only the harmonics. It will create a strong signal in B-mode or a short-lasting multicolored, mosaic-like effect in color Doppler sonography.
Several terms for this typical signal have been used, e.g. induced or stimulated acoustic emission, loss of correlation imaging and sono-scintigraphy.

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From POINT Biomedical Corp
CARDIOsphere® is an ultrasound contrast agent for assessment of myocardial perfusion in patients with coronary artery disease composed of highly echogenic bispheres.
PB127 is a new developed microbubble with a bilayer polymer/albumin shell filled with nitrogen gas that has ideal characteristics for power harmonic Doppler. They can be destroyed by high power ultrasound, and spectral decorrelation between ultrasound pulses is maximized by rapid dissolution of the released nitrogen gas.
POINT Biomedical Corp. announced (March 01, 2004) that it has completed two Phase 3 trials of CARDIOsphere®. The Phase 3 trials were designed to evaluate the performance of CARDIOsphere® imaging relative to radionuclide imaging for detecting obstructive coronary artery disease and identifying the anatomic location of perfusion defects.

From SIUI Inc.;
'The SIUI CTS-200 is one of few 'linear only' units to be developed with a digital scan converter to process all incoming signals. With a digital processor, not only is the incoming signal processed faster but less noise is introduced into the signal path. The images are cleaner, crisper than you have experienced, even in machines at many times the price.'
'CTS-200 is suitable to a wide range of examination of liver, gallbladder, kidney, spleen, pancreas, thyroid gland, breast, uterus, urinary bladder, OB/GYN, etc. It is a portable ultrasound scanner of high performance.'