Abstract: Advanced multiple beam equalization radiography (Amber) has been successfully applied to chest radiography. More recently, the applications have been extended to mammography. The Amber chest unit (Oldelft, Delft, The Netherlands) controls the local X-ray exposure to the patient by means of a feedback loop consisting of a number of detectors in front of the film cassette and the same number of absorbers in front of the X-ray tube. The detector readouts and a predefined compression curve determine the position of the absorbers, while the patient is being scanned by means of a horizontally oriented fan beam. As a consequence, the multiple beam equalization technology has introduced new concepts such as beam profile, compression curve, number of absorbers, and detector weighting function to projection imaging. In order to optimize these different parameters we have developed a computer program, which simulates the multiple beam equalization techniques. Conventionally exposed films are laser scanned resulting in a matrix of optical density values. The program calculates for each pixel the X-ray transmission. These X-ray transmission values are the basis for the simulations with varying beam profile characteristics (i.e. the intensity distribution of the X-ray beam of a channel in horizontal and vertical direction), compression curves, number of channels, detector weighting functions and H&D film curves In order to accurately simulate a particular exposure, the program can be calibrated using optical density and X-ray dose measurements on a conventional X-ray unit or on the Amber unit.!4
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