Improvement of image quality by tilted fan beam data acquisition in a helical scan X-ray CT

The helical scan X-ray CT is useful for high speed acquisition of three dimensional image data. In image reconstruction from helical scan data, a set of sequential data is used and the data are interpolated to produce projection data which reconstruct an image of a given cross section. This interpolation sometimes causes artifacts in the reconstructed image. We propose a new data acquisition method which minimizes the effect of scanning slice position in the axial direction. The proposed method inclines an X-ray detector array in the direction of rotation. The tilted angle is defined as arctan(θL/2Rπtanθ), where L is the moving distance of a table per rotation and R is the radius of rotation of the X-ray source. The angle θ is the orthogonal projection of the half of a fan angle onto the parallel beam projection plane. Simulation results showed that our method eliminated the low frequency distortion and improved the spatial resolution in the axial direction