Abstract
This paper presents a new three-dimensional (3D) imaging method for detecting the spatial structure of a complex inner cavity based on positron annihilation and γ-photon detection. This method first marks carrier solution by a certain radionuclide and injects it into the inner cavity where positrons are generated. Subsequently, γ-photons are released from positron annihilation, and the γ-photon detector ring is used for recording the γ-photons. Finally, the two-dimensional (2D) image slices of the inner cavity are constructed by the ordered-subset expectation maximization scheme and the 2D image slices are merged to the 3D image of the inner cavity. To eliminate the artifact in the reconstructed image due to the scattered γ-photons, a novel angle-traversal model is proposed for γ-photon single-scattering correction, in which the path of the single scattered γ-photon is analyzed from a spatial geometry perspective. Two experiments are conducted to verify the effectiveness of the proposed correction model and the advantage of the proposed testing method in detecting the spatial structure of the inner cavity, including the distribution of gas–liquid multi-phase mixture inside the inner cavity. The above two experiments indicate the potential of the proposed method as a new tool for accurately delineating the inner structures of industrial complex parts.
Highlights
Three-dimensional (3D) imaging techniques based on positron annihilation, as well as the generated γ-photon, have been the focus of recent research especially in the field of medicine
In 2014, the Helmholtz–Zentrum Dresden–Rossendorf research center presented the first 3D image reconstruction method based on PIPA offline γ-photon, which was tested by an FTFE sample embedded with an aluminum cone, a copper ball, and an iron cuboid of a 2.5 cm diameter “Wagner (2014)”; the result demonstrates precision of only a few centimeters, and further improvement is expected for practical applications in industry. 18F is used for marking a glass ball to estimate various technical indexes of a fluidized bed “Hensler (2015)”
Another major concern of introducing the 3D γ-photon imaging method to the industrial field is the high density of industrial parts that are often made of metal and/or alloy compared to the low-density bodies in the medical field
Summary
Three-dimensional (3D) imaging techniques based on positron annihilation, as well as the generated γ-photon, have been the focus of recent research especially in the field of medicine. 3D γ-photon imaging testing method used in the industrial domain remains limited to the stage of theoretic analysis in laboratories, and the detection precision is far from meeting its demand Another major concern of introducing the 3D γ-photon imaging method to the industrial field is the high density of industrial parts that are often made of metal and/or alloy compared to the low-density bodies in the medical field. For such a complex part, scattering is likely to occur when the 511 KeV γ-photon penetrates through it; accurate correction of γ-photon scattering is required for constructing a high-resolution 3D image of its inner cavities.
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