Abstract
Due to the potential of compact imaging systems with magnified spatial resolution and contrast, cone-beam x-ray differential phase-contrast computed tomography (DPC-CT) has attracted significant interest. The current proposed FDK reconstruction algorithm with the Hilbert imaginary filter will induce severe cone-beam artifacts when the cone-beam angle becomes large. In this paper, we propose an algebraic iterative reconstruction (AIR) method for cone-beam DPC-CT and report its experiment results. This approach considers the reconstruction process as the optimization of a discrete representation of the object function to satisfy a system of equations that describes the cone-beam DPC-CT imaging modality. Unlike the conventional iterative algorithms for absorption-based CT, it involves the derivative operation to the forward projections of the reconstructed intermediate image to take into account the differential nature of the DPC projections. This method is based on the algebraic reconstruction technique, reconstructs the image ray by ray, and is expected to provide better derivative estimates in iterations. This work comprises a numerical study of the algorithm and its experimental verification using a dataset measured with a three-grating interferometer and a mini-focus x-ray tube source. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles. This algorithm is of interest for future cone-beam DPC-CT applications.
Highlights
X-ray phase-contrast computed tomography (PC-CT) uses the phase shift that x-rays undergo when passing through matter, rather than their attenuation, as the imaging signal and can provide better image quality in soft-tissue and low atomic number samples
It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles
The experimental dataset that was measured to test the reconstruction algorithms was recorded at a CT setup for differential phase-contrast imaging, based on a three-grating interferometer and a mini-focus x-ray tube source installed in a compact gantry at the Technische Universität München (Munich, Germany)
Summary
X-ray phase-contrast computed tomography (PC-CT) uses the phase shift that x-rays undergo when passing through matter, rather than their attenuation, as the imaging signal and can provide better image quality in soft-tissue and low atomic number samples. Three kinds of iterative reconstruction techniques for fan-beam DPC-CT were proposed, namely, statistical iterative algorithms [32, 41,42,43], simultaneous algebraic reconstruction technique [44] and algebraic iteration reconstruction [45] Those studies demonstrated the feasibility of iterative reconstruction for DPC-CT. We have discretized the cone-beam DPC-CT imaging modality as a system of linear equations and developed a 3D algebraic iteration reconstruction (AIR) algorithm for it. This algorithm is based on the Kaczmarz method [46] or the later rediscovered algebraic reconstruction technique (ART) [47] and reconstructs the image ray by ray. It is shown that the proposed method can reduce the cone-beam artifacts and performs better than FDK under large cone-beam angles
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