Dr Graham Treece, Department of Engineering
wxDicom documentation
CT reconstruction
These controls are all associated with the CT reconstruction parameters. They can be accessed from the 'CT Recon' tab in the control area on the right. Their primary aim is to check that the sampling, filtering and number of angles is appropriate before . However, they can also be used to demonstrate the forward and inverse radon transform on any greyscale image.- Relative Scale
- This controls the spatial sampling for the forward radon transform. A value of 100 will sample at exactly the same spacing as the initial data, which is practically sufficient for most images which already contain some small level of blur. A value of 200 will sample at twice this density, which should always be sufficient.
- Angle Scale
- This controls the number of angles for the forward radon transform. A value of 100 will result in an angular resolution such that changing from one angle to the next will never cause a jump of more than one pixel anywhere in the image. Larger values increase this resolution.
- Filter Parameter
- This controls the power in a raised cosine filter applied to the transform during back projection. A value of 100 disables the filter, hence giving a pure Ram-Lak filter. Lower values increase the filtering.
- Detection Noise
- This controls the amount of noise added after the forward radon transform (i.e. to the sinogram) after reconstruction. Zero means no noise is added.
- Reconstruction Options
- This determines whether to show the sinogram (forward radon transform) or complete reconstruction.
- Reconstruct
- This applies a forward and backward projection on the image such that it is fully reconstructed, with the reconstruction progress visible.
- Reset
- This returns to displaying the original image, which is useful for showing any differences from the reconstruction above.
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