Film-screen sharpness in complex motion tomography

An unsharp radiologic image is created in tomography by the combined motion of the x-ray tube and the film-screen cassette. This image is generally recorded at angles other than normal to the film-screen plane. A metbd for determining the influence of this recording angle on film-screen sharpness is described. The method involves imaging an edge target at various angles between the x-ray beam and the film-screen plane. The MTF is then calculated from the edge images. The effect of film-screen sharpness and quantum noise on subjective image quality in temporal bone tomography is discussed.