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Shin-ichiro Iwamo,Akira Shiozaki 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
In the acquisition of projection data in X-ray CT, logarithm operation is indispensable. But noise distribution is asymmetrically projected by the nonlinearity of logarithm operation, and the precision of the CT number of a reconstructed image degrades remarkably. Previously we proposed a simple correction method of the projection data according to the statistical distribution of noise. But when captured photons are very few, a detector output-signal frequently has negative value and we have to carry out clamp processing compulsorily due to the non-zero/non-negative restriction in the logarithm operation. In this paper, we propose a new method for statistically rectifying not only the influence of the nonlinearity of logarithm operation but also the influence of clamp processing. Furthermore, computer simulations using numerical phantoms are carried out to check the validity of the proposed method, and the quality of reconstructed images is compared with that of a conventional method.