Design of a digital beam attenuator system for chest radiography
We have been testing a digital beam attenuator (DBA) system for fabricating patient- specific compensating filters to improve image quality in chest radiography. At present, the technique is limited by a 2 hour attenuator fabrication time and a 20 mR exposure used to acquire an initial image from which the attenutor is designed. We now are developing an improved DBA system capable of generating, in a few seconds, patient-specific compensating filters for clinical chest radiography. The initial image will be acquired at less than 1 mR of skin exposure using an intensifying screen viewed by a low light-level television camera. Image processing including scatter and beam-hardening corrections generate a 64x64 matrix of values from which the attenuator is fabricated. The attenutor will be fabricated with individual layers having a 16x16 format using a special purpose dot-matrix printer. Successive layers are shifted by a quarter of a dot width to maintain the 64x64 sampling frequency in the final attenuator. After the attenuator is positioned automatically in the x-ray beam, a final image will be acquired directly on film. © 1985 SPIE.
