R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

174 Medical modelling
Closely fi tting masks have been shown to provide a benefi cial effect on
the reduction of scarring resulting from burns, particularly to the face
and neck (1, 2, 3, 4). These masks are typically vacuum-formed from the
strong clear plastic material, polyethyleneterephthalate glycol (PETG).
Traditionally, the vacuum-forming mould is made from a plaster cast of the
patient, which itself is made from an alginate impression. Taking a facial
impression is uncomfortable, time consuming for the patient, and it may be
particularly disturbing following the physical and psychological trauma of
burns.
Published work has indicated that optical scanning and computer-aided
manufacturing techniques can be used for various clinical applications (5,
6, 7) including the fabrication of burns masks (8, 9, 10). The potential
benefi t of this approach is the non-contact nature of the data capture, which
has been shown to be more accurate, quicker, more comfortable and less
distressing for burns patients compared to the traditional impression. The
aim of this research was to explore the practical implications of employing
such an approach to the treatment of facial burns and to assess various
methods of adapting and physically reproducing the data to create a
vacuum-forming mould.
6.9.3 Methods
Three-dimensional surface scanning has been used in industry for many
years to integrate surfaces of objects with computer-generated designs.
Non-contact scanners operate by using structured light or lasers and digital
camera technology to capture the exact position in space of a large number
of points on the surface of objects. Computer software is then used to create
surfaces based on these points. These surfaces can then be analysed or
integrated with CAD models. The general principles of non-contact surface
scanning are described more fully in Section 2.3.
The optical scanner used in this work uses a laser and digital camera
technology to capture the surface of an object (Vivid 900, Konica Minolta
Photo Imaging UK Ltd, Rooksley Park, Precedent Drive, Rooksley, Milton
Keynes, Buckinghamshire, MK13 8HF, UK). This scanner was selected
because the specifi cations suggested that the accuracy, resolution and range
of capture were more than adequate for capturing the human face. It also
benefi ted from ready availability, manufacturer after sales support, comparatively
low price and compact size compared to other systems that have
been reported, which have been specialised and expensive or locally made
prototypes (9, 10).
Although the acquisition time for this type of scanner is only a fraction
of a second, movement would still lead to inaccuracy in the captured data.
Therefore, the patients remained motionless in a comfortable position