A PACS upgrade can preserve core storage while changing behavior around viewers, priors, worklists, routing, reconciliation, launch context, reporting, and third-party integrations. Regression scope should follow dependencies, not just release-note headings.
Start with what changed
Compare versions, configuration, interfaces, and stated implementation behavior. Map each change to the workflows that depend on it, including systems that may not be owned by the PACS team.
Prioritize observable risk
Revalidate high-volume and high-consequence workflows first, then known edge cases and previously fragile integrations. Define expected results before testing so “looks okay” does not become the acceptance standard.