Direct Fan-Beam Reconstruction Algorithm via Filtered Backprojection for Differential Phase-Contrast Computed Tomography

Zhihua Qi,Guang-Hong Chen

doi:10.1155/2008/835172

Abstract

Recently, a novel data acquisition method has been proposed and experimentally implemented for differential phase-contrast computed tomography (DPC-CT), in which a conventional X-ray tube and a Talbot-Lau-type interferometer were utilized in data acquisition. The divergent nature of the data acquisition system requires a divergent-beam image reconstruction algorithm for DPC-CT. This paper focuses on addressing this image reconstruction issue. We have developed a filtered backprojection algorithm to directly reconstruct the DPC-CT images from acquired fan-beam data. The developed algorithm allows one to directly reconstruct the decrement of the real part of the refractive index from the measured data. In order to accurately reconstruct an image, the data need to be acquired over an angular range of at least 180∘ plus the fan angle. As opposed to the parallel beam data acquisition and reconstruction methods, a 180∘-rotation angle for the data acquisition system does not provide sufficient data for an accurate reconstruction of the entire field of view. Numerical simulations have been conducted to validate the image reconstruction algorithm.

Highlights

In recent years, X-ray phase-contrast imaging methods have attracted significant interest
We present an image reconstruction formula for fan-beam differential phase-contrast computed tomography (DPC-CT) which can be utilized to accurately reconstruct DPC-CT images at any fan angle provided that the data is acquired within the angular range of 180◦ plus fan angle
It has been demonstrated that when the image object is relatively large, the fan angle must increase to cover the entire image object, and a parallel-beam approximation cannot be directly applied to reconstruct images

Summary

Introduction

X-ray phase-contrast imaging methods have attracted significant interest. Based upon the phase retrieval method, phase-contrast imaging can be classified into three categories: interferometric methods [1, 2], analyzer crystal methods [3, 4], and free-space propagation methods [5,6,7]. These methods generally require excellent spatial coherence and/or excellent spatial resolution of the detectors. Phasecontrast imaging is normally conducted using highbrilliance synchrotron beam lines or microfocus X-ray tubes. Computed tomography imaging methods have been developed [11, 16] based on the phasecontrast projection images

Results

Discussion

Conclusion