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 geomet ry is optimized for emission at the expense of the transmission data. We hy pothesized that the addition of only a few projections sampling truncated a reas (by shifting the bed/camera) would permit a significant improvement in image quality with only a small increase in imaging time. In parallel geom etry, data are preprocessed and the;additional projections are merged into the original sinogram, thereby partially completing it. For fan-beam data, the projector routine is modified to take into account different bed positi ons. Both cases require the use of an iterative reconstruction algorithm. I mprovements due to partial completion are shown for different increases of total imaging time for both geometries, On simulated and true data, a 15% i ncrease of imaging time led to a better recovery of the truncated area than obtained from a priori knowledge of the body contour.