R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

Case studies 257
6.101 3D reconstruction of data segmented by the standard threshold
for bone (left) and the manually edited data (right).
To improve the data describing the surface of the facial bones required
the extensive use of the manual editing tools in Mimics. Some areas were
improved by using the local ‘Thresholding tools’ within the Edit tools in
Mimics. This allowed small areas to be selected according to higher or lower
densities without affecting the overall segmentation. However, specifi c
areas have to be edited manually using the Edit tools to delete data relating
to soft tissue and draw in data relating to bone. The fl exibility of these
editing tools combined with good anatomical knowledge resulted in accurate
segmentation of the skull. Although this was quite time consuming,
the improved results are well worth the effort and would ensure that the
subsequent facial reconstruction was carried out on the best model
possible.
The inner surfaces of the skulls were more easily identifi ed because the
brains had been removed as part of the mummifi cation process. However,
other areas proved much more diffi cult to pick out from the surrounding
tissue. This was especially the case in the mouth, palate and nasal cavities
where desiccated soft tissue remained in place. The nose also posed problems
due to the presence of cartilage and the fact that the nasal bones were
broken and displaced. Again, this damage resulted from the mummifi cation
process.
The three-dimensional reconstruction functions of Mimics were used to
assess the quality of the segmentation on screen. Finally, the highest quality
three-dimensional reconstructions were created to check the data before
building the models. The fi nal reconstruction can bee seen on the right of
Fig. 6.101.