Estimation and validation of the frequency responses of a scanner system and an image reconstruction system in X-ray computed tomography

In computed tomography, factors that theoretically affect the modulation transfer function (MTF) in the region near the isocenter are the frequency responses of the scanner system (MTF _S ) and reconstruction processing (MTF _A ). Although MTF _S and MTF _A are performance indices that are not disclosed to the users, both can be estimated by the measured MTF with the use of theoretical formulas. In this study, we proposed two methods to obtain the MTF _S and MTF _A , and confirm their validity. The first method to obtain the MTF _S and MTF _A uses a theoretical formula and the measured MTF. Another method uses the measured MTF and the noise power spectrum. In both the methods, the MTF _S and MTF _A were obtained separately. By our proposed methods, performance indices that are not usually disclosed to the users can be known.