# Derivative-Free Iterative One-Step Reconstruction for Multispectral CT

## TL;DR

This paper introduces a new fast and effective method for reconstructing images in multispectral CT without needing derivatives.

## Contribution

A derivative-free iterative algorithm for MSCT image reconstruction with fast convergence and superior performance.

## Key findings

- The proposed algorithm uses a full forward model and a derivative-free adjoint problem.
- It shows faster convergence and better performance than existing methods.
- The method can be generalized with additional regularization and data discrepancy terms.

## Abstract

Image reconstruction in multispectral computed tomography (MSCT) requires solving a challenging nonlinear inverse problem, commonly tackled via iterative optimization algorithms. Existing methods necessitate computing the derivative of the forward map and potentially its regularized inverse. In this work, we present a simple yet highly effective algorithm for MSCT image reconstruction, utilizing iterative update mechanisms that leverage the full forward model in the forward step and a derivative-free adjoint problem. Our approach demonstrates both fast convergence and superior performance compared to existing algorithms, making it an interesting candidate for future work. We also discuss further generalizations of our method and its combination with additional regularization and other data discrepancy terms.