Abstract: A method and apparatus are provided for quickly determining misalignment between two images. Patient misalignment calculations can performed on-line using Fourier correlation analysis to compare the location of a portal field of radiation with a previously stored portal reference field. Fourier comparisons are done in both hardware and software which rapidly computes misalignment of a patient relative to the portal field and can also rapidly reposition the patient with respect to that field.

Abstract: Method and apparatus for producing a fringe pattern corresponding to height and depth gradients of an illuminated object with the fringe pattern lines used to define edges of stacked sheets provided as a filter for X-ray dosage tailoring. A camera is provided to produce the fringe pattern on a photographic film using a compact arrangement of light sources, lenses and gratings all within a convenient housing facilitating use yet at the same time providing sufficient resolution through separation of projection and imaging optics. A laser range finder is additionally provided to insure placement of the object to be X-rayed, typically a portion of the human torso, at a standard distance so that the ultimately produced X-ray filter will be properly sized. The filter is produced by cutting a set of lead sheets with edges corresponding to each of the separate contour lines in the exposed and developed film receiving the fringe pattern.