DICOM PS3.5 2024b - Data Structures and Encoding

10.18 Transfer Syntax for High-Throughput JPEG 2000 Compression

Two Transfer Syntaxes are specified for High-Throughput JPEG 2000 Image Compression (Lossless Only) (HTJ2KLossless and HTJ2KLosslessRPCL), and one for unconstrained High-Throughput JPEG 2000 Image Compression (HTJ2K). Any of these may be negotiated separately and there is no default or baseline specified (other than as described in Section 10.1).


  1. All HTJ2K codecs are required by [ISO/IEC 15444-1] to support both reversible and irreversible wavelet and multi-component transformations. The reason for specifying three separate Transfer Syntaxes in DICOM is to allow an application to request the transfer of images in a lossless manner when possible. The HTJ2K Image Compression Transfer Syntax allows for either lossless or lossy compression to be used at the sender's discretion.

  2. No baseline using other compression schemes is required.

  3. When the pixel data has been received in the HTJ2K Image Compression Transfer Syntax, since it may have been lossy compressed, the waiver of the requirement in Section 10.1 to support the DICOM Default Little Endian Transfer Syntax still applies.

10.18.1 HTJ2K Lossless RPCL

The HTJ2K Lossless RPCL Transfer Syntax allows for progressive display of images, as well as retrieval of thumbnail images.

The progression order shall be RPCL (Resolution Position Component Layer). This sequences the resolution blocks so that lower resolutions can be read first.

The number of decompositions shall be sufficient for the width or height of the base resolution to be <= 64. This permits retrieving a thumbnail resolution image.

The Tile Length Markers (TLM) shall be present. This allows finding the resolution breakpoints to support smart streaming.

The following parameters may improve decoding performance:

  • Block Size: 64x64

  • Number of tiles: 1

DICOM PS3.5 2024b - Data Structures and Encoding