This standards publication describes a method for determining the maximum percent difference between measured distances in an image and actual corresponding phantom dimensions. The procedure described evaluates geometric distortion in three orthogonal planes passing through the center of the specification volume. This procedure does not address the question of the absolute positional accuracy of the image of the test object in the frame of reference of the magnet. Only the relative separation of selected points on the test object is considered. This procedure does not address the measurement of slice flatness or the accuracy of slice positioning.