How is a square grid used to represent a circular cross-section?
If the sensor cross-section is circular, this circular contour must be projected onto the square grid containing typically 1024 pixels. Some of the pixels will lie outside the vessel circumference and the image is therefore formed from those pixels that lie inside the vessel. A typical arrangement which is commonly used is shown in the figure below, where the circular image is constructed using 812 of the available 1024 pixels.
