Figure 1
Illustration of artefacts induced by motion and dynamic processes during a tomographic measurement. The starting point t = 0 for each simulated measurement was the image depicted on the left side with a size of 5122 pixels. Notice that the black frame is a part of the object but only the inner Shepp-Logan phantom and the rectangle were modified while the object was projected from 0° to 180° at a constant rate. The inner part was (a) linearly translated, (b) scaled with a linear decrease of the scaling factor, (c) sheared linearly and (d) ‘dissolved’ by multiplying a mask with linearly shrinking radius. The images in the upper row show the maximum change at the end of the tomographic scan. Each of the corresponding sinograms depicted in the middle row consists of 804 equidistant projections to satisfy angular sampling. Common filtered backprojections of the sinogram data are depicted in the bottom row. They show pronounced artefacts originating from the motion, like false shapes, missing features and non-closed circles. Vertical ‘streaks’ in the 0° and 180° direction are clearly visible in each reconstruction, since temporal and thus structural differences are largest for the corresponding projections.
