Generating the image

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So when you pick up an ultrasound probe, typically it will have crystals arrayed across the face. Sometimes as many as 256, which is what makes these probes so delicate, and often expensive. Each crystal will send out a scan line, that scan line will go out, hit things, come back, and be transmitted back into electrical energy that will be interpreted by the machine to determine what is along that line of insonation. These scan lines will then go across the face of the probe all 256 or 128, or however many scan lines there are, and generate a frame. That frame is essentially a still image which will then be refreshed several times a second (really typically between 15 and 30 times per second or hertz) and that is the frequency of the image frame rate essentially, and that generates a moving image.