DICOM PS3.17 2020c - Explanatory Information

JJJJ.4 Presentation of Multi-energy Images by Legacy Display Systems (Current)
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## JJJJ.4 Presentation of Multi-energy Images by Legacy Display Systems

A legacy, naïve display system can receive a multi-energy (ME) image and may not recognize it as ME image, but rather display the image as a conventional CT image. This may potentially cause clinical misinterpretation, for instance, in the following scenarios:

1. For virtual mono-energetic images (VMI, images similar to those obtained with mono-energetic x-ray beam, in keV), attenuation highly depends on the beam energy (keV), so CT pixel values in VMI images can be very different from those in conventional CT images. Without proper labeling of such images, including the specific keV value used, the reviewer can come to wrong conclusions.

2. HU-based Multi-energy images where CT pixel values have been modified for specific materials (suppressed, highlighted, etc.) look similar to conventional CT images. Without proper labeling of such images, including the identification of the affected materials and the way of modification, the reviewer can come to wrong conclusions.

3. In certain types of Multi-energy images (effective atomic number, electron density, material-specific image containing material concentration), CT pixel values do not represent HU values. Common ROI tools used on such an image will measure and display an average value. Since non-HU values are quite unusual in CT IOD images, there is a significant risk that a common naïve display will either omit the units of measurements (leaving user to assume the material or units), or (which is even worse) will display "HU" units instead.

4. In case of Virtual Non-Contrast images, the pixel values are modified (contrast is removed and pixel values may have been corrected for displacement of one material by another material). Since pixels are modified, there is a risk that the modification is incomplete or the replacement is not adequate.

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DICOM PS3.17 2020c - Explanatory Information