Slide 14 of 21 First Previous Next Last Index

Finally the sinogram must be centered about the rotation axis of the sample. If you think about the image taken at 0 degrees and 180 degrees, these samples should contain the same data, except reversed. But if the images aren’t centered about the rotation axis, there will also be an offset between these two. This offset causes half circles in the reconstruction, as you can see in this image. This offset is found by comparing similar features in the 0 and 180 degree data, and the sinogram is then moved over the correct amount.