Regions in the B-mode image of a cylinder where the location of a point reflector is changed by sound speed variation.

The characteristics of the sonographic image representation of a point reflector caused by beam refraction when the reflector is placed behind a cylinder, are investigated. This cylinder acts on the ultrasonic beam as a lens, which explains the displacement in the observed reflector location(s). A mathematical model was constructed for a sonogram containing a cylindrical object with sound propagation speed different from its surroundings, and an experiment was designed to show the resulting inaccurate positions of the point reflector image. The image representation depends on the ratio of the sound speed in the cylinder to that of its surroundings. Depending on the location of the point reflector, additional artifacts are also observed. These artifacts occur in different regions (i.e., into two groups of regions for higher sound speed, and four groups of regions for lower sound speed in the cylinder).