Fast PET image reconstruction based on SVD decomposition of the system matrix

Data filtering based on matrix pseudo-inverse is a well known but not yet appreciated means of tomographic image reconstruction. Matrix pseudo-inversion step is very demanding in terms of numerical precision and necessary computing power. Ill conditioning of the system matrix in positron emission tomography (PET) results in solutions highly sensitive to noise in the experimental data. In the present work, the feasibility of image reconstruction based on singular value decomposition (SVD) of the system matrix for animal 2-D PET is demonstrated. Analytic detector response accounting for the non-invariant spatial system response is explicitly included into the system matrix. Regularization of the SVD-based solution with the singular spectrum truncation (TSVD solution) derived from spatial resolution analysis is proposed. TSVD reconstruction is fast except for the matrix decomposition step, which is performed once for a given scanner geometry. Reconstructed image quality and quantitation are compared to those obtained with filtered backprojection (FBP) and iterative maximum likelihood technique. TSVD image reconstruction may be a viable alternative to FBP for routine clinical applications