R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

160 Medical modelling
demonstrates the successful use of three-dimensional tomography, surface
laser scans and rapid prototyping in the surgical management and postoperative
evaluation of a patient presenting with maxillary hypoplasia who
underwent surgical maxillary distraction.
6.7.3 Materials and method
Three-dimensional virtual hard tissue images, shown in Fig. 6.36, were
constructed using Mimics software (Materialise NV, Technolgielaan 15,
3001 Leuven, Belgium) from 0.5 mm slice CT DICOM data sets. To identify
tissue type, upper and lower tissue density thresholds on the CT image were
defi ned and the areas between the slices interpolated to improve
resolution. The data was then prepared for medical modelling using stereolithography.
In addition, STL fi les were generated so that the same data
could be imported into the FreeForm ® software (FreeForm, SensAble
Technologies Inc., 15 Constitution Way, Woburn, MA 01801, USA). The
preparation of data for fi le transfer and medical modeling is described in
detail in Chapter 4.
A stereolithography model was then constructed and used to visualize
skeletal discrepancy, simulate surgical movements and adapt surgical distractors,
as shown in Figs. 6.37 and 6.38. The stereolithography process is
described in detail in Section 5.2. The FreeForm ® software was used to
produce a digital clay model allowing further simulation of surgical movements
(see Fig. 6.39).
Three-dimensional facial soft tissue images (see Fig. 6.40) were captured
before and after surgery using two high-resolution Konica-Minolta Vivid
VI900 3D cameras operating as a stereo-pair (Konica-Minolta Sensing
Europe BV, 500 Avebury Boulevard, Milton Keynes, MK9 2BE, UK). The
6.36 Virtual hard tissue images.