EEE.2.3 Polar-Cartesian Conversion

FOR PROCESSING Polar data is specified such that each column represents a subsequent axial (z) location and each row an angular (θ) coordinate. Following Z Offset and Refractive Index Correction, Polar data can be converted to Cartesian data by first orienting the seam line position so that it is at the correct row location. This can be accomplished by shifting the rows Seam Line Index (0052,0036) pixels so that its Seam Line Location (0052,0033) is located at row “A-lines Per Frame * Seam Line Location / 360”. Once the seam line is positioned correctly, the Cartesian data can be obtained by remapping the Polar (z, θ) data into Cartesian (x, y) space, where the leftmost column of the Polar image corresponds to the center of the Cartesian image. Figure EEE.2-2 illustrates the Polar to Cartesian conversion. The scan-converted frames are constructed using the Catheter Direction of Rotation (0052,0031) attribute to determine the order in which the A-lines are acquired. Scan-converted frames are constructed using A-lines that contain actual data (I.e. not padded A-lines). Padded A-lines are added at the end of the frame and are contiguous. Figure EEE.2-2 is an example of Polar to Cartesian conversion.


Figure EEE.2-2 – Polar to Cartesian Conversion