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arXiv · 2606.21405

Geometry Calibration in Tomography with a Differentiable Ray-Based Model

Youssef Haouchat·Aleix Boquet-Pujadas·Sepand Kashani·Philippe Thévenaz·Michael Unser
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Abstract

Geometric misalignments between the nominal and true acquisition parameters in tomography degrade reconstructions. We propose a framework that jointly reconstructs the volume and calibrates the acquisition geometry for arbitrary source--detector configurations. The core of our framework is an x-ray transform operator whose gradients with respect to the acquisition geometry can be efficiently computed with a ray-tracing method of structure and computational complexity similar to those of the forward operator. We represent the volume in a B-spline basis to provide a continuously differentiable model. This results in a better-behaved optimization landscape compared to voxel-based representations. We validate our framework with CT, micro-CT, nano-CT, and positron emission tomography data under a variety of geometric misalignments.

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Youssef Haouchat, Aleix Boquet-Pujadas, Sepand Kashani, Philippe Thévenaz, Michael Unser. 2026-06-19. Geometry Calibration in Tomography with a Differentiable Ray-Based Model. https://arxiv.org/abs/2606.21405

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