The multiplexed holographic gratings can achieve simultaneously three-dimensional imaging of an object with the Bragg
selectivity. The recording conditions of multiplexed holograms for imaging different depths of the object space are
investigated experimentally. We find that the cross talk can be ignored when ΔΖ is approximately more than 2ΔΖ<sub>FWHM</sub>, and the cross talk is degenerate with the increase of the depth separation. Further we adopt the point-spread function
(PSF) of the imaging system to estimate depth resolution of the volume holographic imaging system. Then to avoid
image overlap we examine multiplexed holograms recorded with different Δθ. We also calculate Δθ theoretically, and find that the theoretical value is consistent with the experimental result. The optimized holographic gratings are used to image the resolution target which is located at the different longitudinal positions to simulate a 3D object. The results
demonstrate that the resolution target located at the two different depths can be reconstructed and clearly imaged on
Single photon emission computed tomography (SPECT) is a nuclear medicine imaging technique and widely used in the
clinical applications. SPECT image reflects not only organizational structure but also functional activities of human body,
such as blood-flow and metabolism condition, therefore diseases can be found much earlier. For many clinical
applications, cone-beam geometry is preferred, which can improve count density and spatial resolution, and quantitative
reconstruction of radiotracer distribution inside the body is desired. In this paper, we developed an efficient, analytical
solution to cone-beam SPECT reconstruction with simultaneous compensation for attenuation and distance-dependent
resolution variation (DDRV), as well as accurate treatment of Poisson noise. The simulation results show our
reconstruction framework is feasible.
A volume holographic grating lens can reconstruct the three-dimensional information by conducting multiple
optical slicing of an object based on Bragg selectivity of the volume holographic grating. In this paper, we employ
the point-spread function of volume holographic imaging system to theoretically analyze its imaging resolution. In
the experiments, the volume holographic gratings are made with a spherical reference (SR) and a planar reference
(PR), respectively, and used as volume holographic imaging lens in our imaging system. The longitudinal and
lateral defocusing characteristics of volume holographic lens with SR and with PR are investigated experimentally
by displacing the interested objects from original reference location, respectively. The effects of the parameters of
the volume holographic lens on the longitudinal and lateral resolution are also discussed. The experimental results
show that increasing the size of the volume holographic lens can improve the depth resolution, and in particular, it
has greater influence on SR VHI. The lateral selectivity of SR VHI is more sensitive than that of PR VHI, and the
Bragg degenerate diffraction of PR VHI on the y axis is obviously observed.
In the conventional single photon emission computed tomography (SPECT), reconstruction algorithm requires full
projection data to reconstruct the images, which will be
time-consuming. While in clinic, doctors usually just care about
the region of interest (ROI), such as heart, not whole body, in this case, a local SPECT reconstruction algorithm is
needed to reconstruct the ROI by only using the projection data from the ROI. In SPECT, the non-stationary Possion
noise in the projection data (sinogram) is a major cause to compromise the quality of the reconstructed images. To
improve the reconstruction quality, we must remove the Possion noise in the sinogram before reconstruction. However,
the conventional space or frequency domain de-noising methods possibly remove the edge information, which is very
important for the accurate reconstruction, especially for the local SPECT reconstruction with non-uniform attenuation.
Wavelet transform, due to its excellent localization property, has rapidly become an indispensable image processing tool
for de-noising. In this paper, we tried to find out the properties of wavelet based de-noising methods for local SPECT
reconstruction with non-uniform attenuation. From the de-noising results, we can see that wavelet based de-noising
methods have good performance for local SPECT reconstruction.
We introduce our latest research of the computed tomography Fourier transform imaging spectrometer that combines the advantages of both the computed tomography imaging spectrometer and the Fourier transform imaging spectrometer. In our previous work, there were still some problems such as the optical aberration in the optical system. Therefore, some significant improvements are made on the optical configuration of our new system. In this paper, the computational simulation of our new system is introduced. Both the interferogram-projection cube and the spectrum-projection cube are generated in the simulation experiment, and the filtered back projection algorithm is adopted in the image reconstruction. The results of the simulation demonstrate the feasibility of our new system.