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Department of Engineering |
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Graham Treece
ENGINEERING TRIPOS PART IIA
Module 3G4 - Medical Imaging and 3D Computer Graphics
Titanium cranioplasty
In this work, medical imaging, computer graphics, surface interpolation
and computer-controlled milling are used to create titanium cranial implants
at Christchurch Hospital, New Zealand.
Researchers: Jonathan Carr, Richard Fright and Rick Beatson, now with
Applied Research Associates NZ Ltd .
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Ray-tracing is used to depict bone surfaces within a stack of
CT data slices.
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A user graphically identifies a defect in the skull by highlighting
the sound bone surrounding the defect
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Radial basis function (RBF) approximation is used to fit a surface
to the incomplete depth-map corresponding to the rendered view of the defect.
The surface of the skull is smoothly interpolated across the defect. The
thin-plate spline basis is chosen in this application.
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A computer numerical controlled (CNC) mill produces a model of
the defect and a mold in the shape of the interpolated surface.
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Flat titanium plate is pressed into the mold in a hydraulic press.
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The finished annodised plate fits the mold.
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The perimeter holes in the plate are for the mounting screws and
the central holes allow fluid to circulate. Perforations give the plate a
limited amount of adjustment in theatre.
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The plate is fixed in place with titanium screws.
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Author: Jonathan Carr.
