NDD Format

(This is a work-in-progress description of the format)

Natural DICOM Document (NDD)

The NDD format is a form of syntactic sugar on top of the DICOM JSON Model (the "DJM") with the goal of making DICOM objects easier to understand and operate on using JSON tools in various languages.

Requirements

• Transformations between DJM and NDD must lossless and unambiguous
• NDD must be compatible with standard JavaScript language and JSON tooling
• Rely on consumer of NDD to have access to a data dictionary to understand tags and value representations (datatypes)

Core transformations

• DICOM dataset is an Object (sequence with one element converted to element in NDD, back to one element list in DJM)
• Tags
  • Replace hex tags with corresponding data dictionary names where available
  • Retain hex tags for unknown tags
• Value Representation
  • Drop VR when it is defined in data dictionary
  • Preserve VR in an _vrMap object if needed
  • Since all values are lists in DJM
    • Convert single element (VM=1) lists to single value in NDD
    • Convert single element NDD values to lists in DJM
  • Sequence items in DJM become Objects in NDD (Recursively defined)

Other issues handled in same way as DJM

• Bulk data URIs, inline binary
• Private Attributes
• Special case VR
  • decimal strings that don't map perfectly to JSON Numbers
  • character sets