Case Study
CT Scanner re-calibration without phantom
Darius Rückert
- last updated on Jun 11, 2025
CT systems rely on precise calibration to avoid geometric distortions and ensure accurate imaging. Even minor misalignments can cause noticeable issues in the final images.
These calibration settings can drift over time. More sudden changes, like replacing parts or accidental collisions during scanning, can throw the system completely out of alignment. Traditionally, fixing these issues requires lengthy adjustments by external technicians using specialized calibration equipment.
In this article, we'll show how the Voxray QRT's Self-Calibration tool can quickly solve these problems using any existing scan data, without needing special calibration equipment.
During a routine scan of a large sample, one of our clients faced a critical situation: the X-ray source accidentally collided with the sample.
As a result, the scan images showed significant geometric distortions, which were especially noticeable in helical scan modes.
The team needed to address two urgent questions: how far had the scanner's calibration drifted from its original settings, and was there any damage to the manipulator that would require repair?
Post-collision helical scans exhibiting severe geometric artifacts.
Our self-calibration tool leverages a differentiable model of the X-ray system, allowing us to directly optimize the entire scanner geometry based on any scan data.
This model captures the system's physical characteristics, enabling precise adjustments to key parameters: source positioning, detector alignment, and rotation axes.
By applying this optimization process to the collected data, we can quickly correct calibration errors, even after disruptive events like component collisions. The resulting information helps address mechanical issues and improves future scans, ensuring optimal performance without requiring downtime.
Recalibration of the damaged CT without a calibration phantom, using the Voxray Self-Calibration tool enables high-quality CT reconstruction.
Results
After the collision between X-ray source and sample, our client's helical scans showed significant geometric artifacts.
Using the Voxray Self-Calibration tool, we optimized the system's geometry and eliminated these distortions. This was achieved without needing any calibration phantoms and only took a few minutes.
The analysis revealed a 2.7% error in the vertical motors that control source and detector movement. Once we applied this correction to the geometry, we could again produce accurate reconstructions, as shown in the following images.
2D slice comparison of the battery.
2D slice comparison of the battery.
3D rendering of the battery.
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