R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

18 Medical modelling
2.8 Noise in CT image.
as can be seen in the close up view of the same data shown in Fig. 2.9.
Three-dimensional reconstructions from this data will lead to a poor result
as shown in Fig. 2.10. Typically, such reconstructions will appear rough
surfaced or porous.
If the effect occurs in only a few images, it may be possible to edit them
out to produce a normal looking model. However, this does mean that the
accuracy of the model in these areas cannot be guaranteed. If the whole
data set is affected, this editing is unfeasible and the resulting model may
be too poor to be useful.
2.2.8 Kernels
Modern CT scanning software allows different kernels (digital fi lters) to be
used. These modify the data to give better three-dimensional reconstructions
and can help to reduce noise. Typically, the options will range from
‘sharp’ to ‘smooth’. Sharpening fi lters increase edge sharpness but at a cost