Spatial Resolution of FBP Reconstruction Estimated by Edge Spread Function for Circular Disk: A Simulation Study

抄録

The edge spread function (ESF) in the circular edge method is obtained directly using the reconstructed circular disk, but line spread function (LSF) is determined by differentiating the ESF. We investigated the ESF influenced by subpixel sampling for the filtered backprojection (FBP) images by a simulation study, and estimated the full width at half maximum (FWHM) using curve fitting to ESF assuming the LSF is given as Gaussian function. A phantom consisted of 184 mm background disk and 20 mm signal disk; the contrast was 15%, 7%, and −7%; a 200-mm field of view; image size was 1024 × 1024 matrix and 512 × 512 matrix. Edge of phantom image was blurred by the cumulative distribution function (CDF) of Gaussian function with a known FWHM, and parallel beam projection data with 1024 (512) radial bins and 1024 (512) /180° angular views were reconstructed. The circular edge method is affected by subpixel sampling, differentiation and noise, and CDF Gaussian fitting is effective in reducing the ESF fluctuation. The FWHM by an approximation expression agreed well with that of numerical experiment when FWHM > 0.276 mm for 1024 × 1024 images and FWHM > 0.677 mm for 512 × 512 images.