Comparison of deconvolution techniques to measure directional MTF of FDK reconstruction

To measure a spatial resolution of CT scanner, several methods have been developed using bar pattern, wires and thin plates. While these approaches are effective to measure two dimensional MTF, it is not easy to measure directional MTF using those phantoms. To overcome these limitations, Thornton et al. proposed a method to measure directional MTF using sphere phantoms, which is effective only when the cone angle is small. Recently, Baek et al. developed a method to estimate the directional MTF even with a larger cone angle, but the proposed method was analyzed using a noiseless data set. In this work, we present Wiener and Richardson-Lucy deconvolution techniques to estimate the directional MTF, and compare the estimation performance with that of the previous methods (i.e., Thorntonas and Baekas methods). To estimate directional MTF, we reconstructed a sphere object centered at (0.01 cm, 0.01 cm, 10.01 cm) using FDK algorithm, and then calculated plane integrals of the reconstructed sphere object and the ideal sphere object. The plane integrals of sphere objects were used to estimate the directional MTF using Wiener and Richardson-Lucy deconvolution techniques. The estimated directional MTF was compared with the ideal MTF calculated from a point object, and showed an excellent agreement.