Sunday, January 02, 2011

Acoustic Imaging uses Tiny Microphones in the Heart

IVUS, or Intravascular Ultrasound, is a catheter-delivered imaging mode that can be inserted into the body and into organs, such as the heart, or peripheral arteries, to get a cross-section view.   The images are produced by a method known as pulse-echo, where a transducer, like a very small microphone, is excited with one short tick. That produces a soundwave that propagates out, comes in contact with anything in the direction it is going, and some, often very little, of the energy is then reflected back to the same transducer which by this time has been switched over to a very sensitive preamp to listen for the incoming signal.

This process is repeated many times in a circle, like radar, and over the course of a fraction of a second, an image is built up. The image of course is not something you could actually see with your eyes - it is more like an echo map.

Shown on this series of six are some IVUS images of a beating heart. The two center images are the most interesting, as they show the heart squeezing and opening to pump blood.

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