RIU 324 Lecture Notes - Lecture 53: Grayscale, Frame Rate, Shallow Focus
23 Apr 2020
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Document Summary
After scan conversion into matrix but prior to writing data to image storage. Aka frame averaging, temporal compounding, temporal averaging. Successive frames held in the buffer and averaged to decrease noise. Increases signal-to-noise ratio by combining frames and eliminating echoes that are not the same. Frame rate reduced, thus temporal resolution degraded. Notice that in the frame on the left, there are two signals of identical amplitude that align perfectly (constructive interference). Also notice that the noise from the two signals is neither perfectly in phase or perfectly out of phase (partial constructive interference). Therefore, the signals add to create one signal twice as large, whereas the noise only partially adds to create noise 1. 4 times as large (the square root of 2). Produced by averaging multiple frames, each transmitted at varying angles. The multiple frames improve the snr, and the carying angles diminish the number of specular based image artifacts that appear in the image.
