High-energy X-ray spectrum reconstruction: solving the inverse problem from optimized multi-material transmission measurements

Frontiers in Physics

Physics

A. Walker¹  K. Ginsburger¹  A. Friou² 

[1] CEA, DAM, DIF, Arpajon, France;null;

关键词: spectrum estimation;    flash X-ray;    transmission measurement;    genetic algorithm;    ill-posed inverse problem;   

DOI  :  10.3389/fphy.2023.1257548

 received in 2023-07-12, accepted in 2023-08-28,  发布年份 2023

来源: Frontiers

【 摘 要 】

Reconstructing the unknown spectrum of a given X-ray source is a common problem in a wide range of X-ray imaging tasks. For high-energy sources, transmission measurements are mostly used to recover the X-ray spectrum, as a solution to an inverse problem. While this inverse problem is usually under-determined, ill-posedness can be reduced by improving the choice of transmission measurements. A recently proposed approach optimizes custom thicknesses of calibration materials used to generate transmission measurements, employing a genetic algorithm to minimize the condition number of the system matrix before inversion. In this paper, we generalize the proposed approach to multiple calibration materials and show a much larger decrease of the condition number of the system matrix than thickness-only optimization. Additionally, the spectrum reconstruction pipeline is tested in a simulation study with a challenging high-energy Bremsstrahlung X-ray source encountered in Linear Induction Accelerators with strong scatter noise. Using this approach, a realistic noise level is obtained on measurements. A generic anti-scatter grid is designed to reduce noise to an acceptable -yet still high-noise range. A novel noise-robust reconstruction method is then presented, which shows much less sensitive to initialization than common expectation-maximization approaches, enables a precise choice of spectrum resolution and a controlled injection of prior knowledge of the X-ray spectrum.

【 授权许可】

Unknown   
Copyright © 2023 Walker, Friou and Ginsburger.