Measurement of three-dimensional point spread functions in multidetector-row CT

The recent multidetector-row CT (MDCT) systems yield high spatial resolution in all directions of volumetric images in clinical routine. The quantitative characterization of the performance of MDCT systems is important for comparing the effects of different scan and reconstruction parameters, for comparing between different CT systems, and for evaluating the accuracy of size and density measurements of fine details in MDCT images. This paper presents a method to characterize the performance of MDCT using a three-dimensional (3D) point spread function (PSF) obtained from MDCT images. With separability assumed, the 3D PSF is decomposed into 2D PSF in the scan plane and SSP on the z-axis. The 2D PSF and SSP are modeled on the basis of the symmetric Levy function that generalizes Gaussian and Lorentzian functions. The descriptions of 3D PSF are defined from the Fourier analysis of MDCT images of wire (diameter 0.049mm) and micro-disk (thickness 0.05mm) phantoms. Experimenting with a MDCT system, we demonstrate the method for 3D PSF measurement.