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Published on: October 11, 2016
Moiré fringes of photon counting grating interferometer with single-focal-spot and flat-panel X-ray sources
Wangjiang Wu1, Zengxiang Pan1, Yilin Chen1
1School of Biomedical Engineering, Southern Medical University, Guangzhou, China.
Background:
The cold-cathode flat-panel X-ray sources (FPXS) achieve planar integration of X-ray point sources, which have the potential advantages of cathode addressability and anode patterning tailored to predefined imaging tasks. However, the potential benefits of the FPXS-based grating interferometer (GI) with photon-counting detectors (PCD) remain to be determined.
Purpose:
In this work, we aim to study if the moiré fringes of the FPXS-based photon-counting GI (PCGI) can be formed by utilizing a benchtop system.
Materials And Methods:
To address this issue, a dedicated in-house X-ray research platform was first built to investigate the X-ray characteristics of the FPXS, including the X-ray spectrum and the projection aliasing behaviors. Subsequently, a benchtop FPXS-based PCGI system was constructed. Due to the projection aliasing of the FPXS, the conventional micro-focus and large-focus X-ray sources were employed to adjust the geometric configurations and the grating postures of the PCGI. As a novel large area X-ray emission source, the X-ray emission area sizes and the X-ray intensities of the FPXS were tuned to investigate if the moiré fringes could be formed under different scenarios. In addition, the moiré patterns of the micro-focus and large-focus X-ray sources were obtained as a baseline for the corresponding FPXS PCGI system.
Results:
The current of the FPXS utilized in the study can reach several hundred A at about 40 kV. Moreover, it cannot be independently controlled, which was voltage-dependent and declined with respect to the exposure time. The projection of the FPXS became less blurred as the X-ray emission area decreased; however, the number of emitted X-ray photons was proportionally reduced. The moiré fringes with the single-focal spot X-ray sources were reported under different scenarios, such as low X-ray photon flux, w/wo G0, different energy bins, and different postures of the source. As for the FPXS, however, the moiré fringes were not formulated under different X-ray emission area sizes and shapes due to the factors, such as projection aliasing, low power, and the system instability.
Conclusions:
The unique characteristics of the FPXS were its large-area X-ray emission with spatial addressability. While the projection aliasing of FPXS can be largely reduced with small X-ray emission area size, the X-ray intensities were also significantly compromised and, thus, prevented formulation of the moiré fringes. In future, the moiré fringes of the FPXS-based PCGI system with large area X-ray emission require to be further investigated, such as proposing novel algorithms to obtain the moiré patterns by deblurring the aliased projections.
