Ultrasound waves are reflected when there is a change in acoustic impedance. The larger the change, the more ultrasound is reflected. Microbubbles have an enormous difference in acoustic impedance as compared to surrounding fluid due to the large differences in density, elasticity and compressibility.
At low acoustic power (mechanical index less than 0.1), the mechanism of ultrasound reflection is that of Rayleigh scattering and the microbubbles may be regarded as point scatterers. The scattering strength of a point scatterer is proportional to the sixth power of the particle radius and to the fourth power of the ultrasound frequency;; the echogenicity of such contrast agent is therefore highly dependent upon particle size and transmit frequency. The backscattered intensity of a group of point scatterers is furthermore directly proportional to the total number of scatterers in the insonified volume. The concentration of the contrast medium is of importance.

See also Backscatter Energy, Cross-section Scattering.

The ultrasound bandwidth describes the number or range of frequencies. The reflected Doppler bandwidth increase when the Doppler beam strikes red blood cells traveling at many different speeds (as in turbulent flow).

See also Q-value.

The Germany-based pharmaceutical company is the result of the take-over of Schering AG by Bayer AG in 2006. The Bayer Schering Pharma AG is part of the Bayer HealthCare AG, which represents the pharmaceutical part of the Bayer Group.
The company makes ultrasound, x-ray and MRI contrast media, drugs for treating cancer, multiple-sclerosis, heart and nervous system disorders and severe skin conditions.
In general, its activities are focused on four business areas: Fertility control & hormone therapy, diagnostics & radiopharmaceuticals, dermatology as well as specialized therapeutics for disabling diseases in the fields of the central nervous system, oncology and cardiovascular system.
Currently, Bayer Schering Pharma discontinued the manufacturing and development of ultrasound contrast agents.

Ultrasound Contrast Agents:

The beam pattern shows the relative amplitude of the acoustic pressure as a function of direction relative to the transducer. Beam patterns are three-dimensional. The transmit and receive beam patterns are basically the same.

Beam steering is a method of steering the main lobe of a transducer to a certain direction. Array transducers have the ability to be steered as well as focused. Like focusing, the beam is directed by sequentially stimulation of each element. This feature creates the sector scan by rapidly steering the beam from left to right to give the two dimensional cross sectional image.