16 Oct 2018
An interesting little querk of iterative reconstruction is that it can be fed other data to start with. This is called *priori* data, and is essentially an estimate to begin calculating with. Iterative reconstruction will happily take a blank array as it’s starting point, but depending on the step size of the iterations it might take quite some time to converge.

Read More...
13 Oct 2018
One thing you might have noticed on the posts so far is the circular artifact which occurs towards the edge of all the reconstructions. The circle is the same diameter as the square of the reconstruction image. The reason this occurs is because as we approach the corners of the square, there is less and less data available. Only inside the central circle is where there is a consistant maxima of data with which to reconstuct the image

Read More...
29 Sep 2018
Reconstruction of CT images is a process to *approximate* a solution to the problem. Back-projection and Filtered back-projection (FBP) are methods which do fairly well at low computational cost. Technically there is an ideal solution - the best that can be done with the data available; by looking at the problem as an enormous mass of simultaneous equations you reach the *ideal* solution … at great computational cost.

Read More...
22 Sep 2018
If you want to see inside something, an object, a person, a pet … there are a few ways you can do that. I’m personally a huge fan of taking things apart to find out how they were put together - but it’s not entirely the best approach to finding out what’s inside your cat. Maybe you’d want something a little less destructive. If you have an X-ray machine you can shoot some X-rays through your cat and see how many come out the other end. That’s great for 2D images but cats are notoriously three dimensional so your X-ray will actually be all your cat’s 3D bits stacked on top of each other to the point where it takes some real skill to interpret. That’s why Radiographers and Radiologists get paid the *big* bucks, right?

Read More...