In color Doppler imaging with linear arrays, which shape best describes the color Doppler portion of the image?

• A. Rectangular
• B. Parallelogram
• C. Circular
• D. Elliptical

Answer: (B)

Color Doppler data are gathered along the parallel scan lines produced by a linear array. The region where velocity information is computed and displayed is defined by a block of those lines across a depth range, and when this block is mapped to the screen the edges follow the angled, line-based geometry rather than aligning with the screen’s horizontal and vertical axes. That slanted boundary on the top and bottom while the sides remain effectively parallel creates a four-sided figure with opposite sides parallel—a parallelogram. The other shapes would imply boundaries aligned strictly with the screen axes (rectangular) or boundaries defined by a radial symmetry (circular/elliptical), which isn’t how the color Doppler gating from a linear array is laid out.