Prompt gamma ray (PG) imaging based on Compton camera (CC) has been proposed to realize in vivo verification during the proton therapy. However, due to the inherent geometrical complexity of Compton camera data, PG imaging can be time-consuming and difficult to reconstruct in real-time, while using standard techniques such as filtered back-projection (FBP) or list-mode maximum likelihood-expectation maximization (LM-MLEM). In addition, the imaging quality and spatial resolution of the reconstructed PG images is seriously limited by the finite energy and spatial resolution of CC, as well as the Doppler broaden effect. In this paper, we investigate the performance of in vivo verification via PG imaging with a three-stage Cadmium Zinc Telluride (CZT) pixelated Compton camera during the proton therapy for human head. We demonstrated the real-time PG imaging approach by using Monte Carlo back-projection (MC-BP) and triple events. The prompt gammas were induced by a 69MeV ~ 86 MeV proton pencil beam irradiating the human head phantom, which were simulated by using Geant4 toolkit. The results show that the reconstructions with Compton camera imaging realized nearly real-time PG imaging with a good resolution recovery, as well as provided the accurate estimation of in-vivo verification, thus demonstrating the feasibility in PG-based in-vivo proton range verification with CC.
Computed Tomography (CT) has been an irreplaceable method of non-destructive testing in heavy industry and architectural design for a long time. Although, in recent years, a new CT technology with high resolution and extensive applicability for in-situ large-scale structure inspection of concrete has been applied in production. The complexity of the scanning environment and mechanical vibration during the in-situ press loading can result in artifacts on CT image. To solve this problem, a reconstruction algorithm based on system matrix was implemented to reduce of influence caused by track jitter and undefined scanning track. A simulation experiment was performed to verify the algorithm. The result shows the feasibility of the proposed reconstruction algorithm.
In order to detect deformations of parts during the operating test, a novel dynamic industry computed tomography (ICT) system taking advantage of the rotation of specimens itself was purposed by us. However the stationary parts such as the shell around the turbine tips, which are hardly removed due to some industrial reasons, contaminate the projection data, so the blocks are not easily corrected from the projections as what we did in the traditional detector correction procedure. In this work, an interaction based CT reconstruction algorithm is purposed to deal the problem. First of all, we directly reconstruct the image with the contaminated projection data and an interactive match between the reconstructed image and the prior image is performed according to some obvious features. Then a forward-projection of the matched prior image with the practical geometric parameters is made. The block components in the projection data are estimated by calculating the average difference between the forward projections and the real projections of certain detectors. Finally, a new image can be reconstructed using the corrected data. Furthermore, the efficiency of the purposed algorithm is proved by both numerical simulation and practical experiments.
Hard X-ray phase-contrast imaging has been a hot research field in the last decade. It can provide high sensitivity of
weakly absorbing low-Z objects in medical and biological fields. Grating-based differential phase-contrast (DPC)
method has been paid more attention to because it can work with conventional X-ray tube and shows great potential for
clinic application. Tomosynthesis with the combination of phase-contrast imaging is considered as a promising imaging
method which can significantly enhance the contrast of low absorbing tissues and eliminate the effects of superimposed
tissue on anatomical structures and is especially useful for medical applications such as mammography. In this paper, an
experimental phase-contrast tomosynthesis system is implemented based on a weakly coherent hard X-ray phase-contrast
method proposed by our group recently. The effectiveness of the proposed method is proved by actual experiments.
Multiple information (absorption, refraction and dark-field) of the samples can be retrieved in one single imaging
process by information retrieving methods. Then tomosynthesis reconstructions can be performed based on the retrieved
information. It can eliminate the overlap of the sample structures and provide more extensive image information
compared with conventional tomosynthesis.