QUBYX added ICC Profile Generation to Medical Display Calibration Software PerfectLum

June 27, 2009 - QUBYX took note of new requirements in the DICOM standard supplement 100 and added ICC profile generation into the medical display calibration software PerfectLum. Users can now calibrate to DICOM GSDF or CIE L* luminance response, and at same time correct color-temperature over the entire dynamic range and create an ICC profile for the display. The new version of PerfectLum DICOM calibration tool with ICC profile support is immediately available.

Grayscale is out and color is in.

Color is in, because the technical development in LCD displays and increasing output of LCD panels make shrink the advantage of the grayscale display. Color LCDs offer today high resolution, high luminance and high contrast ratios. And obviously who wants to be limited to shades of gray when there is so much more to see on a PACS workstation? Color overlays have been an integral part of Doppler flow imaging in ultrasound for decades, and most nuclear medicine images are better viewed using color scales. The need for color display in radiology images has only increased with the growth of PET-CT imaging, functional MRI and computer-aided detection. The use of color in graphical user interfaces—things like buttons, scroll bars, and menus—makes them a lot easier to see and understanable for a user. Color displays make so much sense, but how does the DICOM standard handle color?

The DICOM standard had addressed color and DICOM in the supplement 100 and defines that it uses ICC profiles to describe color spaces. Supplement 100 states in part: "An important objective of this supplement is color-rendering consistency. This is achieved by methods similar to those used for grayscale consistency. A device-independent color space is specified, and the output of the color pixel transformation pipeline is defined in that space. Since achieving device-independent representation of color is a non-trivial problem, and one that has already been addressed by the color printing and photographic industries, existing industry standard mechanisms are re-used. Specifically, rather than directly encoding color pixel values in a deviceindependent space, they are instead defined by reference to an embedded color profile, as defined by the International Color Consortium (ICC). "

The ICC color management system is the controlled conversion between the color representations of various devices, such as scanners, digital cameras, displays, film printers, computer printers, offset presses and corresponding media. Each device must have its own ICC profile that describes the characteristics of the device. In medical application the output devices display and printer, and eventually the input device digital camera/microscope are concerned. For each of those devices an ICC profile has to be created. So when calibrating your medical color display, you should create an ICC profile for the display at least once.

Color displays can still be calibrated to DICOM GSDF (Gray Scale Display Function) as the GSDF does describe the luminance reproduction of a display. Obviously a color display also reproduces gray shadows, thus it makes sense to calibrate a color display to DICOM GSDF as well. Similar to DICOM GSDF but for color is the CIE L* calibration. CIE L* is a function that reproduces the sensibility of the human eye on color shades. The display calibration software should also adjust color temperature to a certain known value. That can be for example the reproduction of “clear base” or better a reproduction of one of the CIE standard light sources, like D65, that is in general close to the native color temperature of the display.

Click here to download a trial version of PerfectLum medical display quality control tool.

Developers who want to add ICC profile support to their imaging product are welcome to contact QUBYX to discuss how QUBYX can help.