The Study Of X-ray Luminescence Tomography Imaging

Recently,based on-the principle of optical molecular imaging and computed tomography(CT),the new development of X-ray excitation optical molecular probes opens up new pos-sibility for X-ray luminescence tomography imaging(XLCT).This new imaging modali-ty is realized by X-ray luminescence nanophosphors and optical imaging system based on micro-CT.It can overcome the flaws of present optical imaging and achieve measurement at different angles without the outside noise.We study the X-ray luminescence tomography reconstruction problem based on the transfer theory of lights in biological tissues in this dissertation,which mainly includes the following aspects:1)B-ased on the disadvantages of the-narrow beam XLCT imaging,bioluminescence imag-ing and fluorescence imaging,we propose cone beam XLCT imaging to decrease the s-canning time and X-ray exposure and realize the three dimensional tomography imaging of nanophosphor inclusion.First a bi-modality system of X-ray luminescence tomography and computed tomography was built based on the present micro-CT system in our lab.Based on this system,the forward mathematical model is deduced and different solutions of this model is studied.An incomplete variables truncated conjugate gradient method and permissible re-gion strategy were used for reconstruction to obtain a steady solution.The simulation study illustrates the robust of the proposed method against different view numbers,regularization parameters,data noise and optical parameter mismatch.The study of both simulation exper-iments and physical phantom experiments indicated that the proposed method was feasible to the general case and actual experiments.2)Due to the ill-posed nature of the XLCT inverse problem,the quantitative accuracy in the recovered phosphor concentration cannot be guaranteed with only the optical measurements in the quantitative study of XLCT.Hence,the permissible region strategy and spectrally re-solved optical measurements are employed to alleviate the ill-posedness of the inverse prob-lem in optical imaging.The multi-wavelength luminescent measurements are incorporated to increase the measurement data.Meanwhile,the rough distribution of the luminescent light source in the 3D structure is applied as structural a priori information of the permissi-ble source region(PSR)in the reconstruction.The concentration can be recovered with as low as 6.67%error when structural a priori information of PSR from XCT information is utilized to guide and constrain the phosphor concentration reconstruction algorithm.3)XLCT has become a promising imaging technology for biological application based on phosphor nanoparticles.There are mainly three kinds of XLCT imaging systems:pencil beam XLCT,narrow beam XLCT and cone beam XLCT.Narrow beam XLCT can be re-garded as a balance between the pencil beam mode and the cone-beam mode in terms of imaging efficiency and image quality.The collimated X-ray beams are assumed to be par-allel ones in the traditional narrow beam XLCT.However,it is observed that the cone beam X-rays are collimated into X-ray beams with fan-shaped broadening instead of parallel ones in our prototype narrow beam XLCT.Hence the distribution of the X-ray beams in the physical model is incorporated and the optical data from only two perpendicular directions were collected to further speed up the scanning time.Meanwhile a depth related adaptive regularized split Bregman(DARSB)method is proposed in reconstruction.The simulation experiments show that the proposed physical model and method can achieve better results both in the location error and the intensity error than the traditional split Bregman method and validate the feasibility of method.The phantom experiment can obtain the location error less than 1.1 mm and validate that the incorporation of fan-shaped X-ray beams in our model can achieve better results than the parallel X-rays..