High accuracy geometrical calibration for half-mm animal SPECT imaging

In this study we investigate a specific animal SPECT imaging system with a clinical SPECT detector and a multipinhole collimator insert. High accuracy geometrical calibration is a crucial technique in terms of achieving the high SPECT imaging resolution. The calibration steps include: 1) The SPECT system is modeled with a geometrical projection equation; 2) The centroids of the point source projection are calculated from the acquired experimental data; and 3)The geometrical parameters is determined by minimizing a nonlinear least square cost function. With this calibration technique, Experimental studies shows the best achievable reconstruction resolution is 0.5 mm. Furthermore, the uniqueness of the calibration solution is investigated with a SVD based approach. By experimentally calculating centriod variance of point source projections, quantitative calibration accuracy of the proposed calibration method is studied and suggested minimum projection number of the point source experiments to achieve desired calibration accuracy is given.