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  • Title: [Evaluation method of CT number linearity].
    Author: Yang KC, Lin YQ, Yu XE, Lu GW, Lin MY.
    Journal: Di Yi Jun Yi Da Xue Xue Bao; 2002 Mar; 22(3):241-3. PubMed ID: 12390777.
    Abstract:
    OBJECTIVE: To explore the method for computed tomography (CT) number linearity evaluation. METHODS: The model CTP401 of Catphan500 phantom was adopted to test 43 sets of CT scanners under the same scanning conditions. 1- and 2-order curve fitting of the testing results of each scanner were performed, with the bending of the 2-order fitted curve defined as the degree of CT number non-linearity and the slope of the linear fitting as contrast scale. The 2-norms of the fitting coefficients were calculated for the purpose of fitting quality evaluation. MATLAB 6.1 was employed for programming. RESULTS: The 2-norm of the fitting coefficients of the 2-order fitting curve was approximately 1/10 of that of corresponding linear fitting, indicating that 2-order fitting accorded better to the parent population distribution pattern. The degree of the non-linearity was manifested by the bending of the 2-order fitting curve that increased monotonously with the 2-norm of the corresponding linear fitting. CONCLUSION: It is statistically valid to define CT number non-linearity and contrast scale on the basis of 1 and 2-order fittings of the testing results, which well serves the purpose of quantitative analysis.
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