Bubble destruction describes the microbubble shell rupture by ultrasound pulses. The bubble destruction increases with increasing peak negative pressure and decreasing frequency. The mechanical index is an indicator for the effectiveness of microbubble destruction. Contrast enhanced ultrasound relies on bubble rupture to detect bubbles in small vessels.

See also Negative Bolus.

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.

Bubble specific imaging methods rely usually on non-linear imaging modes. These contrast imaging techniques are designed to suppress the echo from tissue in relation to that from a microbubble contrast agent.
Stimulated acoustic emission (SAE) and phase / pulse inversion imaging mode (PIM) are bubble specific modes, which can image the tissue specific phase.
In SAE mode bubble rupture is seen as a transient bright signal in B-mode and as a characteristic mosaic-like effect in velocity 2D color Doppler.
PIM are Doppler modes and detect non-linear echoes from microbubbles. In pulse inversion imaging modes the transducer bandwidth extends, resulting in improved spatial resolution and more contrast.

See also Contrast Pulse Sequencing, Microbubble Scanner Modification, Narrow Bandwidth, Contrast Medium, Dead Zone.

By Byk-Gulden (now Altana);
The transpulmonary echo contrast agent under development, BY 963, promises to be an excellent ultrasound contrast agent for the noninvasive assessment of left ventricular function. Intravenous administration of BY 963 phospholipid microbubbles improves the reproducibility of e.g. quantitative analysis.