MEASUREMENT OF THE EFFECTIVE SIZE OF THE INPUT PHOSPHOR OF AN X-RAY IMAGE INTENSIFIER

A technique is described, using a mobile radiographic x-ray unit, for determining the effective size of the input phosphor of an image inten sifier (I.I.), in particular for a unit with over-table x-ray tube, un der-table II, and with the I.I. physically inaccessible. The technique s described also enable (1) locating the central axis of the I.I.; (2) the ratio, R, of the dimensions of the radiological image incident up on the front of the I.I. to the dimensions of the image on the monitor screen; and (3) the distance between the input phosphor and the table top, which is needed to determine the distance from focal spot to inp ut phosphor. (C) 1997 American Association of Physicists Medicine.