Limited sinogram completion for transmission SPECT imaging

Truncation artifacts can occur in simultaneous emission transmission SPECT imaging even with parallel geometry, especially when the acquisition geometry is optimized for emission at the expense of the transmission data. The authors hypothesized that the addition of only a few projections sampling the truncated area after a bed/camera shift could permit a significant improvement in image quality with only a small increase in imaging time. Because in parallel geometry, such a shift results in column shifts of the sinogram at each angle, it is straightforward to merge any additional projection into the original sinogram, thereby partially completing it. The resulting data still require the use of an iterative reconstruction algorithm. Improvements due to partial completion are studied in the case of a 90 degree dual-headed camera. Results on simulated and true data show that only 4 completed projections can lead to a better recovery of the truncated area than does the a priori knowledge of the body contour