Consistent Display of Images

DICOM standard introduces the Standardized Display System. A Standardized Display System may be a printer, a monitor, or some other display device that has been calibrated according to the Grayscale Standard Display Function (GSDF). The main feature of such display system is that throughout its display range, equal differences in digital input values correspond to visually equal differences in luminosity. Two Standardized Display Systems will always show the same detail in an image, even if their physical characteristics are different.

The values that can be used as input to a Standardized Display System are called "Presentation Values" ("P-Values"). To map image pixel intensities into P-Values, a Presentation Look Up Table ("P-LUT") is used. It is applied after Modality and VOI LUTs.

Presentation LUT is stored in a Presentation State DataSet.

If a display device is not physically calibrated to comply with GSDF, but its characteristic curve (a table that lists luminosities for each digital input value) is known, it can be calibrated at the software level. In that case, P-Values shall be used as input to a GSDF LUT, which will map them to the device's input values according to GSDF. Thus, a non-standardized device together with its GSDF LUT can be considered as Standardized Display System.

ImageGear Medical component allows to build a GSDF LUT from a device's Characteristic Curve.

ImageGear uses all available LUTs (Modality LUT, VOI LUT, Presentation LUT and GSDF LUT), to build the general 16x8 or 8x8 LUT that maps image pixel values into display input values.