COMBINED CONSTRAINTS FOR EFFICIENT ALGEBRAIC REGULARIZED METHODS IN FULLY 3D RECONSTRUCTION

SPECT systems incorporate the use of one or more rotating gamma camera s which can be equipped with cone-beam collimators to improve the trad e-off between spatial resolution and sensitivity. The geometry of the cone-beam collimators implies that a specific 3D reconstruction algori thm must be applied. Algebraic methods provide the possibility of incl uding the physical characteristics, such as attenuation, Compton scatt er and detector response, in the reconstruction process. However, the reconstruction problem is an ill-posed problem which should be regular ized. This paper presents a 3D algebraic method that combines three re gularizing constraints. These constraints deal respectively with penal izing negative voxels, local noise smoothing and missing data compensa tion. The results presented were obtained from imaging simulations, ph antom data and from a thyroid clinical study of a normal volunteer.