Digital Slide Archive

The core data structure enabling interactive visualization. A WSI is stored as a multi-resolution image pyramid, consisting of a baseline full-resolution layer and a series of progressively downsampled copies. This allows a viewer to fetch only the image tiles corresponding to the current field of view and zoom level, making pan-and-zoom navigation of a 100,000 x 100,000 pixel image feel instantaneous.

• Baseline Layer: The highest resolution, often 0.25 microns per pixel.
• Downsampled Layers: Generated by halving dimensions, creating a factor-of-2 scale space.
• Tile-Based Access: Each layer is subdivided into small JPEG or JPEG2000 tiles for rapid random access over HTTP.

A high-performance search subsystem that moves the archive from a file store to a queryable knowledge base. It indexes both technical metadata extracted from the image file headers and semantic metadata from the Laboratory Information System. This engine must support faceted search across millions of slides.

• Technical Metadata: Scanner type, magnification, objective power, compression type.
• Clinical Metadata: Patient ID, specimen type, stain protocol, diagnosis codes.
• Search Patterns: Enables cohort building by querying 'all H&E-stained liver biopsies from 2023 with steatosis'.

A dedicated subsystem for creating, storing, and versioning human and AI-generated markups directly on the WSI canvas. Annotations are stored as vector geometry in a separate layer from the pixel data, preserving the original image's integrity. The service must handle concurrent access and conflict resolution.

• Geometric Primitives: Points, polylines, polygons, rectangles, and freehand regions.
• Ontology Binding: Each annotation is linked to a controlled vocabulary term.
• Provenance Tracking: Records the creator, timestamp, and algorithmic source of every markup.

An automated workflow that orchestrates the transition of a raw scanner output file into a managed archive asset. The pipeline triggers on file arrival, performs validation, extracts metadata, generates the pyramid if missing, and registers the slide in the system catalog. It must be resilient to vendor-proprietary format quirks.

• Format Parsing: Uses libraries like OpenSlide to read Aperio SVS, Hamamatsu NDPI, and other formats.
• Quality Control Gates: Validates file integrity, checks for missing pyramid levels, and assesses focus quality.
• Event-Driven Architecture: Typically built on message queues for scalable, asynchronous processing.

A security subsystem that enforces granular permissions on slide access and operations, critical for HIPAA and GDPR compliance. It mediates every request to the image server, ensuring a researcher can view a de-identified cohort while a pathologist can annotate their assigned cases.

• Access Levels: Read, annotate, download, and administrative privileges.
• Data Cohorts: Permissions can be scoped to specific projects, studies, or patient groups.
• Audit Trails: Immutable logs of every image access event for forensic analysis.