Application of the ILO International Classification of Radiographs of Pneumoconioses to Digital Chest Radiographic Images

A NIOSH Scientific Workshop

The following content has been adapted from a presentation given at the NIOSH Scientific Workshop: Application of the ILO International Classification of Radiographs of Pneumoconioses to Digital Chest Radiographic Images.

DISCLAIMER: The findings and conclusions in these proceedings are those of the authors and do not necessarily represent the official position of the National Institute for Occupational Safety and Health (NIOSH). Mention of any company or product does not constitute endorsement by NIOSH. In addition, citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of these Web sites.

File Interchange Subgroup - Recommendations

Assumptions

• Focus on NIOSH-specific requirements
• Reusable approach for other similar settings
• Modest number of acquisition sites (≈ 100-200)
• Small number of B Readers (≈ 10)
• Small volume (≈ 2,000 patients per year)
• Limited technical support staff at NIOSH
• All equipment for readers supplied by NIOSH
• Digitized reference set available from ILO 2008
• No printed film but existing film-screen OK at sites’ discretion
• Two proposals
  • short term (≈ 3 month) – CD based workflow & paper forms
  • long term – get a (commercial) off-the-shelf (OTS) PACS

Caveats

• 42CFR 37
  • can’t change a regulation in 3 months
  • is digital permitted under current regulation ?
  • does not seem to be explicitly prohibited
  • lack of authority to insist on CDs if digital ?
• Training
  • can all NIOSH B Readers be trained in 3 months ?
  • in use of digitized reference set
  • in use of equipment

Key requirements

• Acquisition site
  • Pre-qualification of system and transfer process
  • Transfer to NIOSH
• Central site
  • Pre-qualification process and tools
  • Quality control process and tools (including queries to sites)
  • Long term archival and disaster recovery
  • Management of readers
• Readers
  • Receipt of images
  • Performance of read
  • Return of results
  • Disposal of images

CD-based short term solution

• Acquisition sites
  • burn CR/DX to CD from modality or PACS
    • CD will be DICOM GPCDR & IHE PDI profile
    • one patient per CD
    • identity in header as per 42CFR 37.41(m)
    • uncompressed “for presentation” image
    • optional “for processing” image if possible
    • no lossy compression permitted
  • submission of initial pre-qualification CD
• Central site
  • receive CDs and check them
    • correct header identification
    • preliminary check of displayed quality
  • tools required
    • standalone PC + pair of displays + viewer (OTS)
    • automated CD format checker (OTS)
      • IHE PDI tool checks format/compliance of CD
    • automated DICOM file checker (customized)
      • DICOM is CR/DX uncompressed + identity + technique
    • CD duplicator +/- DICOM header editor (OTS)
  • duplicate CDs for archival & disaster recovery
    • make two additional copies
    • local archive/off-site archive/send to reader
    • option: pseudonymize copy sent to reader
    • option: remove site supplied viewer on reader CD
  • send CD + ID paper document to B Reader
  • receive completed paper form from B Reader
  • duplicate CDs for archival & disaster recovery
    • make two additional copies
    • local archive/off-site archive/send to reader
    • option: pseudonymize copy sent to reader
    • option: remove site supplied viewer on reader CD
  • send CD + ID paper document to B Reader
  • receive completed paper form from B Reader
• B Readers
  • equipment installed and calibrated by NIOSH
  • standalone PC + pair of displays + viewer
  • system supplied already configured
    • secure: user/local staff/family no permission to install software, modify system, connect to network
    • single approved viewer already installed
    • digitized reference set already installed
  • complete & return paper evaluation form
  • destroy CD with CD shredder
• Viewer requirements
  • custom or OTS – commercial or open source
  • support pair of calibrated (OTS) 3MP grayscale displays
  • read from DICOM CD (? auto detection of insertion)
  • display single PA CXR left monitor
  • display single reference image right monitor
  • scroll through reference set
  • support all known CR/DX grayscale variants
  • support window level/sigmoid LUT
  • support pan/zoom
  • identification & technique annotation (patient & reference)
  • linear distance measurements (no need to capture/save)

Long term solution

• Central site get OTS PACS/RIS (commercial or open source)
• Acquisition sites
  • continue to submit CDs or
  • submit via Internet (IHE Teaching File & Clinical Trial Export TCE)
    • using centrally supplied software on own PC
    • to read locally created CD or connect to local network
• Central site
  • PACS match identifiers (IHE Import Reconciliation IRWF)
  • long term archival of all images in PACS
  • PACS has off-site archive for disaster recovery
• B Readers
  • view images on PACS remotely & securely via high speed internet
  • completes form (IHE Retrieve Form for Data Capture Profile RFD)
  • re-use same local hardware and displays as for CD solution

Reference Set Requirements

• Assume ILO 2008 for short-term solution
  • highest fidelity digitized data available
  • data used to print digital copies, if “original” film not available ?
  • not re-digitized digital copies
• Choice of DICOM encoding
  • DX “for presentation”, not Secondary Capture
  • contrast adjusted for P-Value grayscale output space
  • window values sigmoid or linear ?
  • replace white borders with black to reduce glare
  • identifying attributes helpful to user, e.g.“3/3 r/r” not “0014”
  • identifying attributes that sort into useful order for comparison
  • spacing attributes added to allow nodule size measurement
  • orientation attributes that allow correct hanging
  • validated to be correct per DICOM standard

Identification in DICOM header

• 42CFR 37.41(m) “Each roentgenogram made hereunder shall be permanently and legibly marked with the name and address or ALOSH approval number of the facility at which it is made, the social security number of the miner, and the date of the roentgenogram. No other identifying markings shall be recorded on the roentgenogram.”
• DICOM attributes that modality operator can enter/change:
  • SSN -> DICOM Patient ID (0010,0020) & Patient Name (0010,0010)
  • Date -> DICOM Study Date (0008,0020)
  • ALOSH approval number -> prefix to Patient ID ??? Study Description ???
• Fixed by field engineer at installation/configuration:
  • Facility name -> DICOM Institution Name (0008,0080)
  • Facility address ->DICOM Institution Address (0008,0081)
• May be constrained by RIS and Modality Worklist
• Central site (NIOSH) may need to clean up during CD copy process