Differentiable Forward and Back-Projector for Rigid Motion Estimation in X-ray Imaging

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Hauptverfasser: Jiang, Xiao, Wang, Xin, Uneri, Ali, Zbijewski, Wojciech B., Stayman, J. Webster
Format: Preprint
Veröffentlicht: 2025
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author Jiang, Xiao
Wang, Xin
Uneri, Ali
Zbijewski, Wojciech B.
Stayman, J. Webster
author_facet Jiang, Xiao
Wang, Xin
Uneri, Ali
Zbijewski, Wojciech B.
Stayman, J. Webster
contents Objective: In this work, we propose a framework for differentiable forward and back-projector that enables scalable, accurate, and memory-efficient gradient computation for rigid motion estimation tasks. Methods: Unlike existing approaches that rely on auto-differentiation or that are restricted to specific projector types, our method is based on a general analytical gradient formulation for forward/backprojection in the continuous domain. A key insight is that the gradients of both forward and back-projection can be expressed directly in terms of the forward and back-projection operations themselves, providing a unified gradient computation scheme across different projector types. Leveraging this analytical formulation, we develop a discretized implementation with an acceleration strategy that balances computational speed and memory usage. Results: Simulation studies illustrate the numerical accuracy and computational efficiency of the proposed algorithm. Experiments demonstrates the effectiveness of this approach for multiple X-ray imaging tasks we conducted. In 2D/3D registration, the proposed method achieves ~8x speedup over an existing differentiable forward projector while maintaining comparable accuracy. In motion-compensated analytical reconstruction and cone-beam CT geometry calibration, the proposed method enhances image sharpness and structural fidelity on real phantom data while showing significant efficiency advantages over existing gradient-free and gradient-based solutions. Conclusion: The proposed differentiable projectors enable effective and efficient gradient-based solutions for X-ray imaging tasks requiring rigid motion estimation.
format Preprint
id arxiv_https___arxiv_org_abs_2508_13304
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Differentiable Forward and Back-Projector for Rigid Motion Estimation in X-ray Imaging
Jiang, Xiao
Wang, Xin
Uneri, Ali
Zbijewski, Wojciech B.
Stayman, J. Webster
Medical Physics
Image and Video Processing
Objective: In this work, we propose a framework for differentiable forward and back-projector that enables scalable, accurate, and memory-efficient gradient computation for rigid motion estimation tasks. Methods: Unlike existing approaches that rely on auto-differentiation or that are restricted to specific projector types, our method is based on a general analytical gradient formulation for forward/backprojection in the continuous domain. A key insight is that the gradients of both forward and back-projection can be expressed directly in terms of the forward and back-projection operations themselves, providing a unified gradient computation scheme across different projector types. Leveraging this analytical formulation, we develop a discretized implementation with an acceleration strategy that balances computational speed and memory usage. Results: Simulation studies illustrate the numerical accuracy and computational efficiency of the proposed algorithm. Experiments demonstrates the effectiveness of this approach for multiple X-ray imaging tasks we conducted. In 2D/3D registration, the proposed method achieves ~8x speedup over an existing differentiable forward projector while maintaining comparable accuracy. In motion-compensated analytical reconstruction and cone-beam CT geometry calibration, the proposed method enhances image sharpness and structural fidelity on real phantom data while showing significant efficiency advantages over existing gradient-free and gradient-based solutions. Conclusion: The proposed differentiable projectors enable effective and efficient gradient-based solutions for X-ray imaging tasks requiring rigid motion estimation.
title Differentiable Forward and Back-Projector for Rigid Motion Estimation in X-ray Imaging
topic Medical Physics
Image and Video Processing
url https://arxiv.org/abs/2508.13304