Intercomparison of four reconstruction techniques for positron volume imaging with rotating planar detectors

Four reconstruction techniques for positron volume imaging have been evaluated for scanners based on rotating planar detectors using measured and simulated data. The four techniques compared are backproject then filter (BPF), the 3D reprojection (3D RP) method for 3D filtered backprojection (FBP), Fourier rebinning (FORE) in conjunction with 2D FBP (FORE + 2D FBP) and 3D ordered subsets expectation maximization (3D OSEM). The comparison was based on image resolution and on the trade-off between contrast and noise. In general FORE + 2D FBP offered a better contrast-noise trade-off than 3D RP, whilst 3D RP offered a better trade-off than BPF. Unlike 3D RP, FORE + 2D FBP did not suffer any contrast degradation effect at the edges of the axial field of view, but was unable to take as much advantage from high-accuracy data as the other methods. 3D OSEM gave the best contrast at the expense of greater image noise. BPF, which demonstrated generally inferior contrast-noise behaviour due to use of only a subset of the data, gave more consistent spatial resolution over the field of view than the projection-data based methods, and was best at taking full advantage of high-accuracy data.