A FULLY 3-DIMENSIONAL RECONSTRUCTION ALGORITHM WITH THE NONSTATIONARYFILTER FOR IMPROVED SINGLE-ORBIT CONE-BEAM SPECT

Conventional single-orbit cone beam tomography presents special proble ms. They include incomplete sampling and inadequate three-dimensional (3D) reconstruction algorithm. The commonly used Feldkamp reconstructi on algorithm simply extends the two-dimensional (2D) fan beam algorith m to 3D cone beam geometry. A truly 3D reconstruction formulation has been derived for the single-orbit cone beam SPECT based on the 3D Four ier slice theorem. In the formulation, a nonstationary filter which de pends on the distance from the central plane of the cone beam was deri ved. The filter is applied to the 2D projection data in directions alo ng and normal to the axis-of-rotation. The 3D reconstruction algorithm with the nonstationary filter was evaluated using both computer simul ation and experimental measurements. Significant improvement in image quality was demonstrated in terms of decreased artifacts and distortio ns in cone beam reconstructed images. However, compared with the Feldk amp algorithm, a five-fold increase in processing time is required. Fu rther improvement in image quality needs complete sampling in frequenc y space.