RIU 324 Lecture Notes - Lecture 52: Frame Rate, Sonographer, Beamforming
23 Apr 2020
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Using multiple transmit foci improves lateral resolution. Since each display line is composed of multiple acoustic lines, using multiple foci, the frame rate is often significantly slower, decreasing temporal resolution. Notice that although there are 3 transmit foci in this example, the frame time is not a full three times longer than for a single focus. This is because three foci does not mean three full lines but rather one short line, one intermediate line, and one full line as shown in this figure. Since transmitting is active, there can only be one focus per transmitted line. Unlike transmitting, receiving is passive , so there can be continuous, dynamic receive focusing. Better lateral resolution can be achieved by dynamically changing the focus on receive, instead of having one fixed receive focal depth. Phase delays introduced in the beam former. Phase delays: large phase delay= shallower focus or steeper delays= shallower focus. Focusing is often accomplished by a combination of :
