For quite some time, our LEMON WEB DICOM Viewer has been running smoothly on Cornerstone v2 — the trusted imaging library that made web-based DICOM viewing simple, fast, and reliable. But as imaging standards and browser capabilities evolve, it was time to give the engine a serious upgrade.

We've now moved to Cornerstone v4, a modern, GPU-accelerated version that brings a noticeable performance boost, cleaner APIs, and expanded functionality for medical image viewing directly within the browser.

Let's dive into what this upgrade means for both developers and end users.

From Cornerstone v2 to v4 – Why the Upgrade?

Cornerstone v2 has served us well, powering the previous generation of web-based DICOM viewers across many medical and educational platforms. However, v2 was built around older WebGL contexts and limited GPU usage, which made it harder to scale for large image stacks and advanced rendering workflows.

With Cornerstone v4, the entire architecture has been re-engineered to take advantage of modern JavaScript modules, WebGL 2.0, and cornerstone-core's rendering engine rewrite. In simple terms — it's faster, smoother, and more future-ready.

The goal of this upgrade wasn't just performance. It was also about modernizing the development workflow, improving compatibility with the latest browser APIs, and laying the groundwork for future features such as 3D volume rendering and segmentation overlays.

What's New in Cornerstone v4

Cornerstone v4 introduces a completely redesigned rendering engine, new toolsets, and cleaner modular structures. Here's what you'll notice behind the scenes — and in front of them.

1. GPU-Accelerated Rendering (WebGL 2.0)

The most immediate difference is in rendering speed. Cornerstone v4 uses WebGL 2.0, which means:

Users viewing large CT or MRI studies will immediately feel the difference — no more sluggishness when flipping through slices or zooming in on fine details.

2. Modern Rendering Engine (ContextPool)

Cornerstone v4 introduces the ContextPoolRenderingEngine, which manages multiple viewports more efficiently.
This allows multiple DICOM viewports to share GPU contexts, making side-by-side comparisons and dual-monitor setups much more fluid.

In our web-app, this upgrade means better multi-viewport performance without the occasional "black canvas" glitches seen in v2 during heavy use.

3. Modular Design and Extensible Tools

The old Cornerstone monolith has now been broken down into smaller, modular packages. This makes it easier to:

For developers, that translates into cleaner code, lighter builds, and easier maintenance — especially when deploying updates.

4. Improved Image Loading and Streaming

Cornerstone v4 optimizes the image loader pipeline. It's now more efficient at handling multiple simultaneous DICOM files and large series.
Combined with compression support and streaming-friendly decoders, it allows for faster initial image previews even while larger datasets continue loading in the background.

This makes the viewing experience snappier — especially over slower connections.

5. Advanced Tooling and Measurement Support

Cornerstone Tools v4 (companion package) introduces better geometry handling, improved event systems, and built-in support for:

All of these have been reimplemented in our updated Lemon Web DICOM Viewer interface, maintaining a familiar layout but with better responsiveness and reliability.

Visual and Functional Enhancements in Lemon Web DICOM Viewer

With the new Cornerstone engine at its core, the Lemon Web DICOM Viewer now provides a more modern interface — and a few under-the-hood upgrades that enhance usability:

You'll also notice cleaner code separation between the upload UI and viewer interface. The "Upload and View" logic is now asynchronous, ensuring a smooth transition from loading state to display.

Backward Compatibility and Testing

Because Cornerstone v4 is a major architectural rewrite, backward compatibility was a key focus during our migration.
We've ensured that:

All existing test files and DICOM datasets from our legacy version were retested under v4 to confirm pixel-level accuracy and consistency.

What's Next

This upgrade lays the groundwork for even more advanced features coming soon:

As we move forward, the new Cornerstone ecosystem allows us to expand confidently — without sacrificing performance or compatibility.

Final Thoughts

Upgrading from Cornerstone v2 to v4 wasn't just a version bump — it was a complete modernization of our web-based medical imaging foundation.

The new version is faster, modular, GPU-optimized, and ready for future medical visualization features. For both clinicians and developers, this marks a major leap forward in what's possible through the browser.

So whether you're exploring a CT scan or experimenting with your own DICOM datasets — our new viewer now gives you the smooth, stable, and high-performance experience you deserve.

Try it now:
Experience the speed and precision of Cornerstone v4 — rebuilt, reimagined, and ready for the next generation of medical imaging.