DICOM UPDATE: DICOM image presentation workshop proves successful

March 1, 1999

DICOM image presentation workshop proves successfulThe conversion of bit data stored in a digital file to a soft-copy image display or hard-copy print is not a trivial process. The so-called "pixel-pipeline," which comprises all the operations that

DICOM image presentation workshop proves successful

The conversion of bit data stored in a digital file to a soft-copy image display or hard-copy print is not a trivial process. The so-called "pixel-pipeline," which comprises all the operations that need to be performed in order to create an acceptable image presentation, has many steps and depends on several attributes that may or may not always be present in the header that accompanies the image.

A major portion of the problems that users encounter with DICOM involve image quality and arise because they were not properly applying this pipeline. For example, differences may appear between the image on the modality monitor and on printed film, or window width and level values may be changed at the CT or MR scanner and not carried over to the workstation. Another issue is masking around images that appear white instead of black, and images that are inverted (black bone, instead of white bone).

To address image display issues such as these, nearly 100 participants from around the world attended the DICOM Image Pixel Presentation workshop, which was held in Washington, DC, Jan. 28 and 29. The objective of this workshop was a dialogue between members of the DICOM Committee and the engineers who are implementing the conversion of bits or bytes to an image on a softcopy display or hard-copy print. Members of the DICOM working groups involved with the standardization of image display presented topics related to pixel encoding and presentation.

The workshop was helpful in explaining in detail how the components of this pixel pipeline are intended to be specified, how they should be implemented, and what are some of the most frequently made mistakes. The large variation among image types, another hurdle to standardized image presentation, was also discussed.

For example, ultrasound images can be encoded with the old (retired) single- and multi-frame ultrasound object or the new single- and multi-frame ultrasound object. There are also several vendors that encode an image using the secondary capture object. Each object is distinctly different, which requires the devices to agree on the object before an image can be exchanged.

In addition, the images themselves have several options for transfer syntaxes; i.e., how the images are encoded within the bit stream. There are also a number of encoding schemes. The variety of options creates challenges for vendors.

The presentation of images on a workstation in a consistent manner is an important issue, and based on the attendance at this workshop, it is clear that this matter is alive within the community of DICOM implementers. The dialogue at this workshop was an important step toward making these DICOM implementations successful.

--By Herman Oosterwijk, president, OTech Inc. (herman@otechimg.com)