SCO & CTO to BTO Conversion

The Format Problem

Breast tomosynthesis was adopted by vendors before the DICOM standard caught up. The result is three incompatible formats in the wild:

BTO — Breast Tomosynthesis Object (Standard)

• DICOM Supplement 125 — ratified in 2008
• Multi-frame MG object with enhanced multi-frame structure
• SOP Class 1.2.840.10008.5.1.4.1.1.13.1.3
• What every modern PACS, viewer, and CAD system expects

SCO — Secondary Capture Object (Hologic)

• Produced by Hologic Selenia and Dimensions systems
• Proprietary format — real pixel data is hidden in private DICOM attributes (7E01,1010)
• Visible pixel data is meaningless placeholder content
• Internal compression uses JPEG-LS (near-lossless, error tolerance of 4)
• Cannot be displayed by standard PACS — requires explicit extraction and re-encoding

CTO — Computed Tomography Object (Siemens)

• Produced by Siemens Mammomat Inspiration, optionally by Revelation
• Single-frame-per-instance — each tomo slice is a separate CT-class DICOM object
• Uses CT SOP Class instead of MG
• Modern PACS may refuse these objects or hang them incorrectly

Why This Matters Now

Facilities hit this problem during:

• PACS migrations — legacy archive contains SCO/CTO studies that won't display on the new system
• Multi-vendor environments — Hologic gantry sends SCO, but the PACS only supports BTO
• Prior study retrieval — outside priors arrive in SCO from referring facilities
• CAD integration — iCAD, Transpara, and Volpara require BTO input
• Archive consolidation — merging data from multiple facilities with different scanner vendors

Without conversion, these studies are invisible to radiologists — they exist in the archive but cannot be displayed, compared, or processed.

How Capacitor Handles It

Inline Conversion During Routing

• Capacitor sits between the modality and PACS
• As studies arrive, Capacitor detects the format (SCO, CTO, or BTO)
• Non-standard formats are converted to BTO in transit before delivery to PACS
• No separate migration step — conversion happens as part of normal routing
• Bidirectional — Capacitor can also convert BTO back to SCO or CTO when a downstream system requires it

Conversion on Prefetch

• When Capacitor prefetches prior studies from an archive or external source, incoming priors may arrive as SCO or CTO
• Capacitor converts inline before delivering to the workstation
• Radiologists see standard BTO regardless of the original format
• No manual intervention required

Managed Bulk Migration

For facilities with large archives of legacy SCO or CTO data, Flux provides managed migration:

• Site assessment — analyze archive contents, identify format distribution
• Pilot conversion — convert a sample batch, validate against PACS and CAD
• Bulk processing — convert the full archive with progress tracking and validation
• Ongoing conversion — Capacitor continues converting new incoming priors automatically

What Gets Converted

Capacitor handles the full complexity of each format:

Integration with CAD and AI

Converted BTO studies work with all major mammography CAD and AI platforms:

• iCAD PowerLook / ProFound AI
• Transpara (ScreenPoint Medical)
• Volpara density and risk assessment
• GE SenoIris / Centricity
• Hologic SecurView (via reverse conversion when required)

Capacitor ensures that CAD, SR, and PR objects remain properly linked to their parent studies after conversion — no ghost studies, no broken references.