Image Intensifier

The standard image intensifier is 9"/6". Most systems built after mid-90s have tri-mode IIs with 9"/6"/4.5" IIs.  When considering field of view, it can be said that the smalles, 4.5" is not clinically necessary and not worth the trade-off of higher dose. Manufacturers use technical aspects of the camera and lens assembly in order to more efficiently provide an image, some resulting in comparatively lower dose in the 4.5 field of view.