18 research outputs found
Low dose and fast grating-based x-ray phase-contrast imaging using the integrating-bucket phase modulation technique
X-ray phase-contrast imaging has experienced rapid development over the last
few decades, and in this technology, the phase modulation strategy of
phase-stepping is used most widely to measure the sample's phase signal.
However, because of its discontinuous nature, phase-stepping has the defects of
worse mechanical stability and high exposure dose, which greatly hinder its
wide application in dynamic phase measurement and potential clinical
applications. In this manuscript, we demonstrate preliminary research on the
use of integrating-bucket phase modulation method to retrieve the phase
information in grating-based X-ray phase-contrast imaging. Experimental results
showed that our proposed method can be well employed to extract the
differential phase-contrast image, compared with the current mostly used
phase-stepping strategy, advantage of integrating-bucket phase modulation
technique is that fast measurement and low dose are promising.Comment: 14 pages, 6 figure
Design of a full-filed transmission X-ray microscope with 30nm resolution
A full-field transmission hard X-ray microscope (TXM) with 30nm resolution
was designed and its prototype was constructed. The TXM relies on a compact,
high stiffness, low heat dissipation and low vibration design philosophy and
utilizes Fresnel Zone plate (FZP) as imaging optics. The design of the TXM was
introduced in detail, including the optical layout, the parameters of the FZP,
the mechanical design of the TXM instrument. Preliminary imaging result with
52nm spatial resolution was achieved
Model-driven CT reconstruction algorithm for nano-resolution X-ray phase contrast imaging
The low-density imaging performance of a zone plate based nano-resolution
hard X-ray computed tomography (CT) system can be significantly improved by
incorporating a grating-based Lau interferometer. Due to the diffraction,
however, the acquired nano-resolution phase signal may suffer splitting
problem, which impedes the direct reconstruction of phase contrast CT (nPCT)
images. To overcome, a new model-driven nPCT image reconstruction algorithm is
developed in this study. In it, the diffraction procedure is mathematically
modeled into a matrix B, from which the projections without signal splitting
can be generated invertedly. Furthermore, a penalized weighed least-square
model with total variation (PWLS-TV) is employed to denoise these projections,
from which nPCT images with high accuracy are directly reconstructed. Numerical
and physical experiments demonstrate that this new algorithm is able to work
with phase projections having any splitting distances. Results also reveal that
nPCT images with higher signal-to-noise-ratio (SNR) would be reconstructed from
projections with larger signal splittings. In conclusion, a novel model-driven
nPCT image reconstruction algorithm with high accuracy and robustness is
verified for the Lau interferometer based hard X-ray nano-resolution phase
contrast imaging
A method for material decomposition and quantification with grating based phase CT.
Material decomposition (MD) is an important application of computer tomography (CT). For phase contrast imaging, conventional MD methods are categorized into two types with respect to different operation sequences, i.e., "before" or "after" image reconstruction. Both categories come down to two-step methods, which have the problem of noise amplification. In this study, we incorporate both phase and absorption (PA) information into MD process, and correspondingly develop a simultaneous algebraic reconstruction technique (SART). The proposed method is referred to as phase & absorption material decomposition-SART (PAMD-SART). By iteratively solving an optimization problem, material composition and substance quantification are reconstructed directly from absorption and differential phase projections. Comparing with two-step MD, the proposed one-step method is superior in noise suppression and accurate decomposition. Numerical simulations and synchrotron radiation based experiments show that PAMD-SART outperforms the classical MD method (image-based and dual-energy CT iterative method), especially for the quantitative accuracy of material equivalent atomic number
One-step Method for Material Quantitation using In-line Tomography with Single Scanning
Objective: Quantitative technique based on In-line phase-contrast computed
tomography with single scanning attracts more attention in application due to
the flexibility of the implementation. However, the quantitative results
usually suffer from artifacts and noise, since the phase retrieval and
reconstruction are independent ("two-steps") without feedback from the original
data. Our goal is to develop a method for material quantitative imaging based
on a priori information specifically for the single-scanning data. Method: An
iterative method that directly reconstructs the refractive index decrement
delta and imaginary beta of the object from observed data ("one-step") within
single object-to-detector distance (ODD) scanning. Simultaneously, high-quality
quantitative reconstruction results are obtained by using a linear
approximation that achieves material decomposition in the iterative process.
Results: By comparing the equivalent atomic number of the material
decomposition results in experiments, the accuracy of the proposed method is
greater than 97.2%. Conclusion: The quantitative reconstruction and
decomposition results are effectively improved, and there are feedback and
corrections during the iteration, which effectively reduce the impact of noise
and errors. Significance: This algorithm has the potential for quantitative
imaging research, especially for imaging live samples and human breast
preclinical studies