Analysis and evaluation of the MTF of Cone-beam CT

摘要

The qualities of initial reconstructed images suffer from reduced resolution due to all kinds of factors which are relative to the cone-beam CT imaging system. The blurring is one of the most difficult problems caused by imaging system. To suppress the blurring in the reconstructed image, some research has been conducted on the deconvolution using a point spread function (PSF), but Modulation Transfer Function (MTF) is used here instead of PSF. The MTF can be obtained by application of the two-dimensional (2-D) Fourier transform to the point-spread function (PSF).In this paper, the impact of various factors on MTF is subsequently illustrated with computer simulations. We use numerical phantom to calculate the MTF, and analyze its variation with position. The size of X-ray focus and magnification are also two important factors which influence MTF, so their effects on MTF are simulated. In addition, different longitudinal positions also influence the MTF. Finally, we use 3D Feldkamp and Radon transform algorithm to reconstruct the images respectively. By comparing the results obtained from the two representative reconstruction algorithms, the characterization of MTF of the cone-beam CT algorithm can be evaluated.