Pencil Beam Based X-ray Luminescence Computed Tomography Imaging of Deep TargetsThree-dimensionally and Quantitatively

X-ray luminescence computed tomography (XLCT), especially pencil beam based XLCT, has been emerged for more than 15 years because it can image deep targets in tissue with high spatial resolution and high measurement sensitivity. However, its application is limited by long scanning time and the tedious efforts of finite element mesh generation for model based reconstruction. Our previous study has addressed the imaging speed issue. In this study, we propose to reconstruct XLCT with weighted filtered back projection (wFBP) which makes it possible to perform XLCT imaging three dimensionally for complex objects at a high spatial resolution. We have also proposed measurements with multiple detectors to obtain quantitative XLCT images. To evaluate the proposed methods, we have performed numerical simulations and different sets of phantom experiments including phantom experiments with a control contrast target, different concentrations, and different target sizes. We have also successfully reconstructed deep targets with a diameter of approximately 0.15 mm. For the phantom experiments with targets of different concentrations, using a 4-channel XLCT system and the wFBP, we achieved the ratio of 3.8:1.79:1, closely resembling the ground truth ratio of 4:2:1. Lastly, we have, for the first time, reconstructed different 3D targets at high spatial resolution, successfully, including a printed M target, a triangular hollow bar, and a hot background cuboid with "UCM Li Lab" slots. Our results indicate that the proposed wFBP advances the promising XLCT technology and makes it ready for in vivo studies in the future.