SecretariatMedical Imaging & Technology Alliance (MITA)
Lisa Spellman, dicom@dicomstandard.org
ChairsAllan Noordvyk, Change Healthcare
Justin Ryan, Phoenix Children’s Hospital
wg17chairs@dicomstandard.org
Last strategy update2016-11-05
MinutesWG-17 minutes

 

Scope

  • To facilitate a way to store/query/retrieve 3D models, intended for 3D manufacturing, as DICOM objects (Work Item 1). The approved Work Item is focused on (a) leveraging the existing and growing ecosystem of DICOM-capable systems in use in healthcare institutions and (b) leveraging standards already in use in the 3D printing industry.

Roadmap

  • WG17 will continue fact-finding to support Sup/208 and ensure the approach is supported by users, academics, and industry in the similar fashion we approached for Sup/205.
  • At RSNA 2018, co-chairs and general secretary will investigate whether augmented reality, virtual reality, and mixed reality has high enough adoption to consider DICOM WG17’s review for an additional work item.

Past Work:

  • Completion of Sup/205 and adoption into the 2018b specification of DICOM.

Current Status

  • Proposal of formation.

Current Work Items

  • WG17 completed Supplement 205, DICOM Encapsulation of STL Models for 3D Manufacturing for the encapsulation of the STL 3D file format. This supplement became part of the 2018b DICOM specification.
  • WG17 has an internal draft for Sup/208 for the encapsulation of advanced 3D file formats.
  • WG17 conducted broad-based survey in April 2017 to understand which of the following 3D model file formats should be encapsulated: GCODE, STL, X3D, AMF, 3MF, OBJ, PLY, VRML
  • STL was file format most frequently used
  • Followed by X3D/VRML, OBJ, and 3MF
  • Other formats were rejected
  • WG17 has decided to delay review of Sup/208 by WG06 until it has more information regarding the encapsulated file formats.
  • WG17 is currently developing a ‘marketing’ video to support adoption of DICOM 2018b’s adoption of Sup 205.

Risks

  • 3D printing community is eager for fast progress.
    • Slow progress may result in DICOM proposals being ignored by non-standard, workarounds that become entrenched but hamper interoperability (e.g. private element embedding in secondary capture objects)
  • Might not be able to recruit enough 3D printing stakeholders.
    • However, current level of enthusiasm for a standards-based approach in both end-user and vendor community appears high.

Challenges and Opportunities

    • Closed: STL has been IANA registered
    • Open: OBJs licensing is currently unknown
    • DICOM WG17 continues to lack legal clarification from Autodesk on the licensing of the OBJ file format. We have received email correspondence with their legal counsel supporting an open license, but have yet to receive a signed letter affirming support.
    • OBJ will need IANA registration
    • Open: WG17 to investigate further reducing the number of formats for encapsulation in 208.
    • Open: WG17 is seeking to develop a translation tool to enable users to wrap and unwrap STLs into the DICOM format in order to promote adoption.
    • Co-chairs are investigating opportunities at Change Healthcare and Arizona State University to develop this open source tool.
    • Open to other groups participating in this effort.
    • WG17 and Kevin O’Donnell are currently ‘manually’ generating example WG17 documents.
    • Open: Encourage users and industry to find agreement on advanced file formats for 3D visualization and 3D printing.
    • Currently, OBJ, X3D, and 3MF are the leading formats. The RSNA F2F will have this as a priority item for discussion.
    • Open: Virtual reality is increasing in adoption, but it appears unclear which formats are leading in adoption and whether a lead format is of a FRAND licensing to support encapsulation by DICOM.

Relationship to Other Standards

  • As explained above, a goal of the WG would be to allow for direct compatibility with existing file format standards of the larger (i.e. non-medical) 3D printing community and industry. The most commonly used non-proprietary file format standards for 3D printing are:
    • G-CODE: The G-CODE (RS-274) file format provides the typical means by which precise instructions are sent to 3D printer hardware to construct each layer of the model. Thus, is it mainly used as a final step representation intended for a specific printer, loaded with specific consumable materials. This is typically produced from STL (see below).
    • STL: The stereolithography (AKA standard tessellation language) file format is essentially the lingua franca of 3D printing. While lacking many of the more advanced concepts of other later formats and being very verbose, its simplicity and longevity has allowed it to become the most common format for interoperable exchange of designs between various pieces of 3D printing software, whether medically-oriented or not.
    • VRML: Virtual Reality Modeling Language (ISO/IEC 14772-1:1997) is favored by some software for its ability to represent structures at a more abstract object-oriented level than STL. Use of VRML has in many cases been superseded by X3D (see below). VRML is often used as an intermediate precursor to STL creation.
    • X3D: As defined by ISO/IEC 19775/19776/19777, X3D is an XML-based format built as an extension of VRML/WRL, to address more advanced concepts. It is favored by some software for its ability to represent structures at a more abstract object-oriented level than STL. However, many of its concepts (e.g. lighting control) are aimed more at creating 2D projection images than physical objects. X3D is often used as an intermediate precursor to STL creation. X3D is in current use at the NIH for medical 3D printing.
    • AMF: The Additive Manufacturing File Format (ISO/ASTM 52915:2013) is a relatively new XML file format gaining in use in the 3D printing community. Unlike STL, VRML and XML, AMF was designed with the intent to specifically to address 3D printing. AMF is favored by some software for its ability to represent structures at a more abstract object-oriented level than STL and also describe materials. While it is sometimes used as an intermediate precursor to STL and/or G-CODE creation, but some 3D printers are now able to use AMF directly, obviating the need for use of these other formats. There is currently active debate within the community as to whether AMF or 3MF (see below) should supplant STL as the new lingua franca of 3D printing.
    • 3MF: A competing file format to AMF with much the same capabilities, but much more compact in file size. Invented by Microsoft, it is now published and promoted by a multi-vendor consortium. Like AMF, some 3D printers are now able to use 3MF directly, obviating the need for use of these other formats. There is currently active debate within the community as to whether AMF (see above) or 3MF should supplant STL as the new lingua franca of 3D printing.
    • PDF (U3D): The Portable Document Format with 3D extension (supported in Adobe 8 and above) is used to allow medical staff to preview 3D models prior to printing, without recourse to platform-specific specialty software. It is not possible to use this format to actually produce a 3D printed object. In the 3D printing context its only purpose is preview. This format should be compatible with the existing DICOM Encapsulated PDF IOD, but the current lack of reference to source images in that IOD is a concern (that could be addressed in a manner similar to CP 1559 “Reuse reference mechanisms from General Image Module in other contexts”).
  • The potential future roadmap could involve representation of intermediate segmentation steps. This may touch on standards beyond those listed above and/or involve harmonization/extension of existing DICOM IODs related to 3D visualization