Advanced 4-dimensional cone-beam computed tomography reconstruction by combining motion estimation, motioncompensated reconstruction, biomechanical modeling and deep learning

4-Dimensional cone-beam computed tomography(4D-CBCT)offers several key advantages over conventional 3DCBCT in moving target localization/delineation,structure de-blurring,target motion tracking,treatment dose accumulation and adaptive radiation therapy.However,the use of the 4D-CBCT in current radiation therapy practices has been limited,mostly due to its sub-optimal image quality from limited angular sampling of conebeam projections.In this study,we summarized the recent developments of 4D-CBCT reconstruction techniques for image quality improvement,and introduced our developments of a new 4D-CBCT reconstruction technique which features simultaneous motion estimation and image reconstruction(SMEIR).Based on the original SMEIR scheme,biomechanical modeling-guided SMEIR(SMEIR-Bio)was introduced to further improve the reconstruction accuracy of fine details in lung 4D-CBCTs.To improve the efficiency of reconstruction,we recently developed a U-net-based deformation-vector-field(DVF)optimization technique to leverage a population-based deep learning scheme to improve the accuracy of intra-lung DVFs(SMEIR-Unet),without explicit biomechanical modeling.Details of each of the SMEIR,SMEIR-Bio and SMEIR-Unet techniques were included in this study,along with the corresponding results comparing the reconstruction accuracy in terms of CBCT images and the DVFs.We also discussed the application prospects of the SMEIR-type techniques in image-guided radiation therapy and adaptive radiation therapy,and presented potential schemes on future developments to achieve faster and more accurate 4D-CBCT imaging.

Crustal architecture and metallogeny associated with the Paleo-Tethys evolution in the Eastern Kunlun Orogenic Belt,Northern Tibetan Plateau

The Eastern Kunlun Orogenic Belt(EKOB)in the Northern Tibet Plateau hosts a wide variety of metal deposits related to the Late Paleozoic to Mesozoic magmatism.In this study,we investigate the spatiotemporal distribution of the Late Paleozoic to Mesozoic granitic rocks and associated metal deposits in the EKOB and provide a comprehensive compilation of the geochronological,geochemical and isotopic data on these rocks.We compute regional zircon Hf isotope and crustal thickness maps from the data,based on which a comprehensive model is proposed involving subduction(ca.270–240 Ma),continental collision(ca.240–224 Ma),and post-collisional extension(ca.224–200 Ma)for the Late Paleozoic to Mesozoic Paleo-Tethys evolution in the EKOB.Zircon Hf isotopic and crustal thickness mapping of Late Paleozoic to Mesozoic magmatic rocks was carried out to evaluate their spatio-temporal and genetic links with the regional metallogeny.The polymetallic Fe-skarn and porphyry Cu(Mo)deposits in the EKOB are located above the Moho uplift region,featuring a comparatively thin crust.Granites associated with porphyry Cu(Mo)and polymetallic Fe skarn mineralization are commonly characterized by highε_(Hf)(t)and younger T_(DM)cvalues,whereas granite related to Cu-Mo-Sn skarn deposits exhibit more variableε_(Hf)(t)values,T_(DM)c ages,and the crust thickness,which suggest that more crustal materials contributed to the formation of Cu-Mo-Sn skarn deposits than those for porphyry Cu(Mo)and polymetallic Fe skarn mineralization.In contrast,vein-type Au deposits are located primarily where the Moho surface displays a depression,i.e.,where the continental crust is relatively thick.The magmatic rocks associated with Au mineralization are characterized by lowε_(Hf)(t)and high T_(DM)cvalues,representing reworked ancient crustal components,similar to those associated with porphyry Mo and epithermal Ag-Pb-Zn-(Au)deposits.Our study indicates that the emplacement of magmatic-hydrothermal deposits was controlled by the crustal structure and magma sources.

Structural,electrical and photoluminescence properties of Er^3+-doped SrBi4Ti4O15-Bi4Ti3O12 inter-growth ceramics

Er^3+-doped SrBi4Ti4O15-Bi4Ti3O12(SBT-BIT-xEr^3+,x=0.00,0.05,0.10,0.15 and 0.20)inter-growth ceramics were synthesized by the solid-state reaction method.Structural,electrical and up-conversion properties of SBT-BIT-xEr^3+ were investigated.All samples showed a single phase of the orthorhombic structure.Raman spectroscopy indicated that the Er^3+ substitution for Bi^3+ at A sites of the pseudo-perovskite layer increases the lattice distortion of SBT-BIT-xEr^3+ ceramics.The substitution of Bi^3+ by Er^3+ leads to a decrease of dielectric loss tanδ and an increase of conductivity activation energy.Piezoelectric constant d33 was slightly improved,but dielectric constant was decreased with the Er^3+ doping.The SBT-BIT-xEr^3+ ceramic with x=0.15 exhibits the optimized electrical behavior(d33~17 pC/N,tanδ~0.83%).Moreover,two bright green(532 and 548 nm)and one red(670 nm)emission bands were observed under the 980 nm excitation.Optimized emission intensity was also obtained when x=0.15 for the SBT-BIT-xEr^3+ ceramic.Therefore,this kind of ceramics ought to be promising candidates for multifunctional optoelectronic applications.