Calibrating diagnostic monitors with IMPAX means that IMPAX can take the pixel values from the images captured at the acquisition station and map them to the diagnostic monitor so that the images are displayed correctly.
For example, if a monitor is calibrated incorrectly, or IMPAX is using the wrong calibration type for the monitor, the contrast and brightness of the image displayed on-screen is affected.
Types of calibration
IMPAX supports two types of calibration for diagnostic monitors:
NEMA calibration. This type of calibration is recommended for grayscale diagnostic monitor, and is based on DICOM Part 14. NEMA calibration uses a perceptually linear curve to translate images to the diagnostic monitor.
Gamma calibration. This type of calibration is only used for older monitors and not normally recommended. When Gamma calibration is selected, IMPAX uses a default monitor brightness and ambient light values to convert the images for display on the diagnostic monitor.
Steps to calibrate monitors
Calibrating monitors involves two steps:
Calibrating the physical monitor. Use the calibration tools shipped with the diagnostic monitors to calibrate them. For most monitors, the tools calibrate the diagnostic monitors to the NEMA standard.
Setting the calibration type IMPAX uses. In IMPAX you must select the type of calibration used for the diagnostic monitors at a station. One calibration type is used for all the monitors at the station.
 | Note: To calibrate color monitors used in diagnostic settings, contact your Agfa representative for recommendations. |
How calibration translates image data to the diagnostic monitor
Displaying an image on a diagnostic monitor involves a series of steps that translates the original image into an image that is displayed correctly for interpretation.
An image, which is made up of pixel data, is acquired at the modality.
A window level value is applied to the image.
The image is sent to IMPAX, where a modality-specific presentation LUT is applied to the pixel data. This LUT, which is defined in the Study Presentation Manager in the Administration Tools, translates the pixel data to p-values, a perceptually linear scale. (PACS administrators define LUTs for the entire site, based on the input of the modality vendors. Normally, the presentation LUT is set to Data are Linear p-values. Older modalities use the Gamma-Corrected Video setting.) Refer to “Study Presentation Manager” (topic number 9367) in the Administration Tools component of the IMPAX 6.5.1 Server Knowledge Base.
The p-values are then translated to the pixel values on the monitor and the image is displayed. The mapping of the p-values is determined by the monitor calibration setting you selected in IMPAX. Normally, the calibration type is NEMA.