Exposure equalization radiography of the chest: clinical comparison of slit and raster scanning techniques

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Abstract
Exposure equalization radiography systems with scanning slit and raster geometries were constructed and tested with 75 patients. The scanning equalization radiography (SER) technique uses a detector, placed behind the patient, connected in a feedback loop to a microprocessor-controlled x-ray source. The detector monitors the transmitted radiation, and in turn the x-ray output is varied to equalize the radiographic film density over the entire image. The clinical evaluation of these systems included 25 posteroanterior (PA) chest radiographs by an SER slit-geometry system (5.0-sec scan time), 25 PA chest radiographs by an SER raster-geometry system with an 8.8-sec scan time, and 25 PA chest radiographs by an SER raster-geometry system with a 4.7-sec scan time. These SER radiographs were compared to conventional radiographs of the same patients by two radiologists. The observers noted that the SER slit radiographs had seriously overexposed areas in 80% of instances, and that any potential gains from this sys...