Abstract
In this research, a high-energy in-line phase contrast tomosynthesis prototype was developed and characterized through quantitative investigations and phantom studies. The prototype system consists of an x-ray source, a motorized rotation stage, and a CMOS detector with a pixel pitch of 0.05 mm. The x-ray source was operated at 120 kVp for this study, and the objects were mounted on the rotation stage 76.2 cm (R1) from the source and 114.3 cm (R2) from the detector. The large air gap between the object and detector guarantees sufficient phase-shift effects. The quantitative evaluation of this prototype included modulation transfer function and noise power spectrum measurements conducted under both projection mode and tomosynthesis mode. Phantom studies were performed including three custom designed phantoms with complex structures: a five-layer bubble wrap phantom, a fishbone phantom, and a chicken breast phantom with embedded fibrils and mass structures extracted from an ACR phantom. In-plane images of the phantoms were acquired to investigate their image qualities through observation, intensity profile plots, edge enhancement evaluations, and/or contrast-to-noise ratio calculations. In addition, the robust phase-attenuation duality (PAD)-based phase retrieval method was applied to tomosynthesis for the first time in this research. It was utilized as a preprocessing method to fully exhibit phase contrast on the angular projection before reconstruction. The resolution and noise characteristics of this high-energy in-line phase contrast tomosynthesis prototype were successfully investigated and demonstrated. The phantom studies demonstrated that this imaging prototype can successfully remove the structure overlapping in phantom projections, obtain delineate interfaces, and achieve better contrast-to-noise ratio after applying phase retrieval to the angular projections. This research successfully demonstrated a high-energy in-line phase contrast tomosynthesis prototype. In addition, the PAD-based method of phase retrieval was combined with tomosynthesis imaging for the first time, which demonstrated its capability in significantly improving the contrast-to-noise ratios in the images.
Highlights
Digital tomosynthesis (DTS) is an emerging x-ray technology with the potential to provide retrospective reconstruction of an arbitrary number of plane slices from a single image acquisition sequence
2405 Wu et al.: High-energy in-line phase contrast tomosynthesis x-ray imaging prototype providing in-line phase contrast tomosynthesis has recently been developed by combining the methods of in-line phase contrast and DTS imaging
The results show the fundamental characteristics of noise and spatial resolution for the in-line phase contrast tomosynthesis prototype without introducing the reconstruction algorithm
Summary
Digital tomosynthesis (DTS) is an emerging x-ray technology with the potential to provide retrospective reconstruction of an arbitrary number of plane slices from a single image acquisition sequence. In-line phase contrast projection imaging can generally be performed with direct phase-sensitive projections, which can demonstrate the edge enhancement effect at the interfaces and boundaries of different materials or tissues.. The interfaces between boundaries of different tissue areas are significantly enhanced in a phase contrast image, the bulk of the phase contrast in a given tissue area may be lost if the phase shifts vary slowly. This occurs because phase contrast is proportional to the Laplacian and gradient differentials of the phase shifts. As shown in our previous works, phase retrieval can exhibit the phase-shift differences among different materials by enhancing the overall image contrast rather than providing edge enhancement
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