new approach to scatter correction in SPECT images based on Klein_Nishina equation

ABSTRACT

Scattered photon is one of the main defects that degrade the quality and quantitative accuracy of nuclear medicine images. Accurate estimation of scatter in projection data of SPECT is computationally extremely demanding for activity distribution in uniform and non-uniform dense media. The objective of this paper is to develop and validate a scatter correction technique that use an accurate analytical model based on Klein_Nishina scatter equation and compare Klein_Nishina scatter estimation with triple energy window. In order to verify the proposed scattering model several cylindrical phantoms were simulated. The linear source in the cylindrical Phantoms was a hot rod filled with 99mTc. K factor defines as the ratio of scatter resulting from MC simulation to scatter estimated from Klein_Nishina formula. Also a SPECT/CT scan of the image quality phantom was acquired. Row data were transferred to a PC computer for scatter estimation and processing of the images using MLEM iterative algorithm in MATLAB software. The scatter and attenuation compensated images by the proposed model had better contrast than uncorrected and only attenuation corrected images. The K-factors that used in proposed model doesn't vary with different activities and diameters of linear source and they're just a function of depth and composition of pixels. Based on Mont Carlo simulation data, the K_N formula that used in this study demonstrates better estimation of scattered photons than TEW. Proposed scattered correction algorithm will improve 52.3% in the contrast of the attenuated corrected images of image quality phantom