Optimal display processing for digital radiography

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 (ΔD/ΔlogE) and latitude of 1.47 (ΔlogE for ΔD = 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.

Duke Scholars

Author Ehsan Samei Radiology