Adaptive spatial filtering technique for storage phosphor radiography in portable chest radiographs. Parameter optimization

The optimal parameters of adaptive spatial filtering (ASF) in storage phosphor radiography for processing portable chest radiographs were investigated. Two types of weighting factor curves starting at 383 digital pixel values (PV) (type B) and at 511 PV (type C) were selected for the optimization of ASF. The PV of 27 areas of apparent pulmonary lesions and seven retrocardiac areas were measured for original unprocessed and ASF-processed images. Three radiologists compared 30 ASF-processed portable chest radiographs with apparent pulmonary or pleural lesions with unprocessed images. PV measurements revealed no significant change in pulmonary densities in type B, and an increase in PV of lower pulmonary densities in type C. Densities of retrocardiac areas were more enhanced in type C than in type B. Observer testing showed that pulmonary densities were evaluated as unchanged in 90% of type B images and 76% of type C images. Changes in mediastinal densities were evaluated as adequate in 80% of type B and 90% of type C images. The starting point of the weighting factor curve of ASF in portable chest radiographs should be set the same as in chest radiographs in the upright posteroanterior position with high kVp. (author)