Computer Assisted Prefabrication of a Cranioplasty Implant
Medical imaging is in common use in the field of medicine. The purpose of medical imaging is to try to reconstruct the information hiding behind the image itself. Medical imaging is necessary for the development of many different medical applications. For this reason, in this study, we adopt this technique to develop the cranioplasty surgical planning platform.
Often, victims of accidents endure head injury and trauma that causes serious and sometimes life-threatening damage to the skull. When this happens, a surgical operation is required to repair the damaged skull. This type of operation involves the preparation of craniofacial implants. Cranioplasty is the reconstructive surgery of large defects in the cranial regions caused by trauma or intracranial surgery. The purpose of cranioplasty is to provide protection for the regions of the brain where the cranium is damaged. Patients who have had cranioplasty surgery are usually more susceptible to trauma because they suffer from seizures or visual impairment. The goal of this research is to reconstruct the harmonic contours of the damaged cranium and give it an aesthetic appearance.
Historically, surgeons have reconstructed craniofacial defects according to their individual clinical experience. This made it difficult to predict and analyze the quality of the hand-made implants. Linney et al. proposed the mirror method of generating patient-specific implants. Computer graphics techniques such as surface interpolation with radial basis functions, proposed by Carr et al., are also used to reconstruct the outline of defects and produce implants. We designed the cranioplasty surgical planning platform using computer-aided design (CAD) and medical imaging techniques. The framework of our system is described as follows:
- Input medical images and re-slicing preprocessing
- Segmentation module
- Surface reconstruction and smoothing
- Implant design module
- Display module
- Output surface files in the STereo Lithography (STL) format
The system accepts input files in the Digital Imaging and Communications in Medicine (DICOM) format. For implant design purposes, preprocessing is necessary for re-sampling or re-slicing the 3D volume. The user can re-sample the volume with user-specified resolution parameters or re-slice the volume aligning the user specified direction. Fig. 6 shows the iso-surfaces of the skull generated from the original volume in the left image and the re-sliced volume in the right image. The system also provides segmentation functions in the segmentation module, reconstructs the surface mesh, and smoothes the mesh.
The implant design module is specially developed for the construction of implants used in cranioplasty surgery. Our system includes a mirror method for the implant design module function. Healthy bone structures can be mirrored by the user-defined middle line of the skull to reflect and create the structures of the virtual implant. Fig. 7 shows an example of the mirror method function in the implant design module. The display module provides both 2D slice-view and 3D surface-view functions. When a surface model is created using the surface reconstruction function, the user can save the model in the STL file format.
ˇ¶ Fig. 6. Re-slicing comparison
ˇ¶ Fig. 7. Example of mirroring function
ˇ¶ Fig. 8
ˇ¶ Fig. 9. X-ray pictures after the surgery.