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Ultrasonic B-scanners may provide a simple or compound scan. A simple scan provides an image which is made up of a series of parallel or diverging scan lines such that each point in the tissue is interrogated from a single direction. Most real-time scanners produce these simple scans. This has a theoretical disadvantage in that a reflecting surface which is oblique to the ultrasound beam produces an echo which is reflected away from the receiving transducer such that some reflecting surfaces may not appear on the scan image. In fact most biological surfaces are not perfect specular (mirror type) reflectors but do reflect some sound back along the line of the transmitted sound beam. Thus the images produced by simple scanners are usually satisfactory.
Compound scanners produce linear (parallel line) and sector (divergent) scans during the scanning process which are overlaid on the resulting image so that echoes are received irrespective of the orientation of the surfaces being represented. Hand- operated static B-scanners produce compound scan which is why they are sometimes preferred to real-time scanners. See also B- scanner, Linear array scanner, Sector scanner, and Section scanner.
Content and Design Copyright 2000 Dr. Malcolm C Brown. See Title Page for more details