Ultrasound

Ultrasonic imaging utilizes acoustic energy to form an image of the body. A beam of high frequency (3-10 Megahertz) acoustic energy is directed into the body. Acoustic energy that is reflected from body tissues is detected by an acoustic transducer (typically located near the source) and transformed into an image. Typically, the sound source and transducer are mounted together on an hand held probe. The sonographer, places the probe against the body, and moves it to obtain images of various parts of the body. Most ultrasound machines consist of a linear array of transducers, and produce an image representing a pie- shaped slice of the body. One of the prime advantages of an ultrasonic imager is that it produces images in real time.

Ultrasonic imaging poses many problems to the visualizer. Because of the freely maneuverable probe, the spatial sampling of the produced data is both inhomogeneous and unpredictable. Methods for determining the spatial relationship of the ultrasound data exist-some techniques fix a mechanical arm to the probe that measure its location and orientation; another technique mounts LED's on wands attached to the probe and cameras mounted in the room track the probe. However, once the position and orientation of the probe are known, the data is still sampled in very irregular intervals, and defies many image processing techniques. Ultrasound images typically contain a large amount of noise, termed speckle, that adds to the problem of identifying structures.

Medical Imaging Techniques
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