System and method for converting scan data

An ultrasound device generates polar-coordinate image data divided up into an (N×M) array of polar-coordinate image data blocks; a first external memory configured to store the (N×M) array of data blocks; a second external memory configured to store x-y coordinate image data corresponding to the polar-coordinate image data; a video processing chip comprising an internal memory configured to store an (N×R) array of the polar-coordinate image data blocks; and a controller configured to perform a data conversion operation on the (N×R) array of data blocks to generate x-y coordinate image data, and to store the x-y coordinate image data to the second external memory. N, M, and R are integers greater than 1; R is less than M; and an internal access time for the internal memory element is shorter than an external access time for the first external memory element.