DICOM Encoded Image Profile - Brief Proposal

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1. Proposed Workitem: Proposed Profile: DICOM Encoded Image

  • Proposal Editor: Don Mimlitch
  • Date: N/A (Wiki keeps history)
  • Version: N/A (Wiki keeps history)
  • Domain: Radiology and Cardiology

2. The Problem

DICOM Encoded Images (jpeg baseline, jpeg extended, jpeg 2000, RLE etc.) created by an Modality or Image Archive sometimes cannot be processed or displayed properly by the receiving Actor (image Archive or Display Station). This can be caused by poorly formed encoding, color spaces not supported by the Display or other problems with the encoding/decoding.

3. Key Use Case

An Ultrasound Modality sends a YBR Image with RLE encoding to an Image Manager/Image Archive. An Image Display does a DICOM Image Retrieve requesting the Image as Unencoded (i.e. Uncompressed) The Image Archive sends the Image to the Display as Uncompressed YBR since conversion of YBR to RGB is a lossy algorithm and this conversion is not allowed by the DICOM Standard. The Image display displays the image as if it were RGB which looks very wrong. This is a case as an Image Archive we handle it by having a Configuration Parameter to force the conversion to RGB even though it violates the DICOM Standard. There are many other uses cases we have seen where the Encoding is badly formed or has other problems or the display has problems display an image of a certain type (e.g. bit depth bigger then 8-bits) or other problems.

4. Standards & Systems

DICOM Standard Part 5. JPEG Standard. JPEG 2000 Standard. RLE Definition in DICOM Part 5.

5. Discussion

There is an Inter-Operability problem between Actors which is IHEs main purpose to resolve. If Images can only be properly encoded/decoded or displayed if the same vendor is used for all actors, that defeats the purpose of the DICOM Standard. The proposed profile will probably have one Required Encoding (JPEG Baseline) and the other Transfer Syntaxes will be Options. It might be better to require both JPEG Baseline and JPEG 2000 Lossy to make the Profile more applicable to modern Encodings. Some of the other problems we have seen in image Encoding/Decoding or Display are:

  • JPEG or JPEG 2000 Images encoded with JFIF headers which the DICOM Standard does not permit.
  • Images sent to a Display in Planar format and the Display displays it as if it were Interleaved.
  • Images Encoded without the required Segment Table and Image Separators.
  • Displays which do not handle the Bit Depth of a Negotiated Transfer Syntaxes. Such as RLE 16-bit Images or JPEG Lossless 12-Bit Images.

By having an IHE Profile vendors can specify what Encodings should be Inter operable and vendor can verify their inter operability with other vendors at the IHE Connectathon.