<title>Optimal display processing for digital radiography</title>

Abstract

Display processing is used to transform digital radiography raw data in log-signal units to display values for presentation using a workstation or film printer. Radiographic appearance with respect to subject latitude and detail contrast varies significantly depending on the signal equalization and grayscale rendition used for processing. A human observer study was conducted to define the latitude and detail contrast that is judged optimal for a broad spectrum of chest radiographs. Raw data for 12 chest radiographs acquired with storage phosphor digital radiography systems were transformed using 52 different combinations of latitude and detail contrast. For specific latitude values, contrast was adjusted by varying the equalization gain. Three radiologists at three different medical centers evaluated the images. Each image was compared to a reference image using a calibrated display on a computer workstation. For PA views, processing that produced a detail contrast of 3.14 (∆D/∆logE) and latitude of 1.47 (∆logE for ∆D = 1.75) was determined to be best for all cases and was achieved with an equalization gain of 2.64. For lateral views, a detail contrast of 3.42 and latitude of 1.17 was best for all cases (gain = 2.29). For individual cases, the preferred processing varied from the global average primarily with respect to latitude.

Neonatal Chest Computed Radiography: Image Processing and Optimal Image Display

“…Despite the presence of CR in pediatric imaging for nearly 20 years [9], to our knowledge no scientific methodology has been developed for addressing specific soft-copy viewing preferences. Years ago, a hard-copy CR film included two images, one imitating a screen-film radiograph and a second that enhanced edge structures, such as catheters [8,9]. Currently, one hard-copy CR film melds the screen-film appearance and edge enhancement.…”

“…Soft-copy image display parameters must be controlled to prevent interacting effects from confounding dose-reduction experiments. Soft-copy image display preferences for adult chest CR were determined in a previous study [8], but requirements for soft-copy image display preferences for neonatal chest CR are unknown. Because of concerns about radiation sensitivity in children, research is being conducted into methods of reducing radiation dose in CR.…”

“…The raw image data were processed with a prototype image-processing algorithm [8]. Three variables were altered: brightness, detail contrast, and latitude.…”

“…One hundred ten combinations of 140 possible combinations of each patient's image were made. The processing parameter matrix was not symmetric, and the narrower-latitude and lowerdetail contrast images were not acquired because observation [8] had shown the range of lowest latitude and contrast performed the worst. With this criterion, 30 image combinations per patient were eliminated without alteration of the results, allowing reduction of computational time and enhancement of observer participation.…”

“…These radiologists were familiar with soft-copy interpretation. Each radiologist rated each image on a nine-point viewing scale relative to the control image as in previously published adult work [8]: 4, image quality markedly better, diagnosis likely altered; 3, image quality clearly better, diagnosis might be altered; 2, image quality somewhat better, diagnosis should be the same; 1, image quality slightly better, diagnosis will be the same; 0, no difference; -1, image quality slightly worse, diagnosis will be the same; -2, image quality somewhat worse, diagnosis should be the same; -3, image quality clearly worse, diagnosis might be altered; -4, image quality markedly worse, diagnosis likely altered.…”