SASI — A computer code for megavolt X-ray focal-spot diagnosis

The focal-spot intensity-distribution is generally measured by imaging an opaque aperture on a 2D position-sensitive detector, and by applying an appropriate decoding algorithm on the image. The square aperture method [1, 2] comprises a simple algorithm and, contrary to other methods, is insensitive to geometrical uncertainties. In addition, artifacts caused by crimps, scratches and irregularities in the detector, intensifier or collimator are easily eliminated. SASI («Square Aperture Spot Imaging») is a computer code designed to provide a user-friendly tool to derive the focal-spot intensity-distribution from the original digital image. The code is written in MA TLAB^®. A recap of the mathematical basis is provided followed by a full description of the structure and operation of the SASI code. Detailed demonstrations of the code´s capabilities are presented for actual X-ray shots.