Apparatus for determining the position and orientation of an x-ray source

A frame for determining the position and orientation of an x-ray source relative to an x-ray cassette during x-radiography. In one embodiment the frame includes an x-ray transparent or translucent plate having a first surface and a second surface; and a partially radio-opaque protrusion positioned on the first surface of the plate. In another embodiment, a method for determining the position and orientation of an x-ray source relative to an x-ray cassette is disclosed. The method includes the steps of providing a frame, including an x-ray transparent plate having a first surface and a second surface; and a protrusion having a radio-opaque portion positioned on the first surface of the plate, and placing the plate on the x-ray cassette such that the second surface is in contact with the x-ray cassette. The method further includes placing the appendage on the plate in close juxtaposition to the protrusion, exposing the appendage and plate to an x-ray beam, and examining the image formed.