Fundamental imaging describes ultrasound imaging and Doppler modes in which the received signal is acquired and processed under the assumption of linear propagation and scattering.

See also Contrast Pulse Sequencing.

Harmonic is an oscillation of a system at a frequency that is a simple multiple of its fundamental frequency. The fundamental frequency of a sinusoidal oscillation is called the first harmonic. The second harmonic has a frequency doubled that of the fundamental.

See also Fundamental Imaging, Harmonic Imaging, Subharmonic Imaging and Superharmonic Imaging.

Superharmonic imaging uses higher harmonics like third and fourth harmonic to increase the contrast to tissue ratio compared to a second harmonic imaging mode. Second harmonic imaging is better than fundamental imaging, but has limited capabilities to discriminate between tissue and microbubbles, caused by the non-linear propagation of ultrasound.

(CHI) Contrast harmonic imaging is an ultrasound technique to improve the measurement of blood perfusion or capillary blood flow. Based on the nonlinear properties of contrast agents, CHI transmits at the fundamental frequency but receives at the second harmonic. Contrast enhanced echo signals contain significant energy components at higher harmonics (bubbles acts as harmonic oscillators), while tissue echoes do not. Caused by that contrast signal can be separated from tissue echoes by the characteristic signal.
In combination with the pulse inversion technique, CHI promises very high contrast agent sensitivity with high spatial resolution.

See also Ultrasound Contrast Agent Safety and Hemoglobin.

(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.