Three-dimensional imaging of flat natural and cultural heritage objects by a Compton scattering modality
Characterization and interpretation of flat ancient material objects, such as those found in archaeology, paleoenvironments, paleontology, and cultural heritage, have remained a challenging task to perform by means of conventional x-ray tomography methods due to their anisotropic morphology and flattened geometry. To overcome the limitations of the mentioned methodologies for such samples, an imaging modality based on Compton scattering is proposed in this work. Classical x-ray tomography treats Compton scattering data as noise in the image formation process, while in Compton scattering tomography the conditions are set such that Compton data become the principal image contrasting agent. Under these conditions, we are able, first, to avoid relative rotations between the sample and the imaging setup, and second, to obtain three-dimensional data even when the object is supported by a dense material by exploiting backscattered photons. Mathematically this problem is addressed by means of a conical Radon transform and its inversion. The image formation process and object reconstruction model are presented. The feasibility of this methodology is supported by numerical simulations.
Compton scattering imaging system with two scanning configurations
Abstract. The judicious use of Compton scattered radiation continues to be a relevant challenge for the future of tomographic imaging. In this context, a new modality of Compton scattering tomography has been recently proposed. This new system has the advantage of being fixed, with a source and detectors placed on a ring passing through the source. The objective of this paper is to explore new possibilities for this new modality: scanning both small and large objects via a double scanning configuration. In fact, when an object under study is small and can be placed inside the detector ring, its scanning will be performed by the interior configuration. Otherwise, a large object placed outside the system will be scanned by the exterior configuration. The modeling of data acquisition of these two scanning modes leads to a new Radon transform on circular arcs (CirArcRT), established for the first time. Image reconstruction requires the inversion of CirArcRT, which is obtained via geometric inversion (GI). In fact, GI allows converting the circular arcs into corresponding half-lines, and consequently, the CirArcRT into a new Radon transform on half-lines, whose inversion is established. Numerical simulations are carried out to demonstrate the feasibility of the new modality. The ability for the same system to scan both small and large objects enlarges the fields of applications for tomography from biomedical imaging to nondestructive testing in industry as well as cultural heritage objects imaging.
A novel inverse problem in γ-rays emission imaging
This article presents a recent result on the feasibility of reconstruction of the radioactivity distribution of an object from a sequence of Compton-scattered radiation data in emission imaging. This may be regarded as a novel inverse principle as opposed to the traditional one in which the object is reconstructed only from the non-scattered rays collected at different incident directions. The new inversion procedure is described by an invertible linear integral transform which may be viewed as a generalized Radon transform and has several advantages over the old one. It improves significantly the contrast of the reconstructed image. The required data for reconstruction is easily acquired from an energy and position sensitive gamma camera under the form of scattered distribution images classified by their Compton-scattering angle. The motion of the camera in standard tomographic procedure is here no longer necessary for data taking.