Transducers may be focused by internal focusing and external focusing.  These are accomplished by

Rayleigh scattering occurs if the particle dimensions are 

An increase in reflection amplitude from reflectors that lie behind a weakly attenuating structure is called

Enhancement is caused by 

The amount of dispersion in the far field of an ultrasound beam can be decreased by

Improper location of an echo may be attributable to

A shortened spatial pulse length results in 

What type of noise is associated with Doppler shift? 

What ultrasound method requires two active elements mounted side by side? 

A curving vessel within a color-flow image shows color in the vessel when the beam and vessel are parallel but shows no color, as the vessel turns perpendicular to the beam. The loss of color means that