An improved scan converter (100) for converting received echo signals representative of the amplitude of ultrasound energy returning grom sampled points along a plurality of spaced apart paths distributed in an image space into signals to be displayed as display pixels in a raster scan display system (150). The scan converter includes a scan data memory (120) for storing the received echo signals in quadrants of the scan data memory. Each quadrant is associated with even and odd numbered paths and sample row combinations. Sample rows are related to sample points along the spaced apart paths. The scan converter further includes a circuit (1000) for determining a gray scale value to be assigned to each selected display pixel based on a predetermined combination of four received echo signals adjacent the selected display pixel and chosen from the quadrants of the scan data memory. The improved scan converter is capable of operation in both linear and sector scan modes, and, when in the sector mode, over 90° and 180° sectors.