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LASER PHOTOPOLYMERISATION MODELS BASED ON MEDICAL IMAGING : A DEVELOPMENT IMPROVING THE ACCURACY OF SURGERY

Objective


The Phidias project has proved that it is possible to produce accurate medical models based on medical image data. The selective colouring of medical models has been developed, so that all relevant information from the images can be transfered to the surgeon.

Each element in the process chain for the manufacturing of medical model has been elaborated in the project.

Improvements have been made to the images generated with Spiral CT, the most suited approach for medical model data acquisition. The noise level and artefacts due to spatial inhomogeneities have been reduced.

Approaches to enhance the results of image based segmentation have been investigated and implemented. This has resulted in a userfriendly environment for the medical data processing.
A special image enhancement technique to prevent over- and undersegmentation has been developed. Thanks to this approach the interactive efforts required for tasks such as femur and pelvis separation in the hip joint can be reduced up to 90 %. In addition the quality of the resulting surface improves.
Support for 3D interaction in regions of interest pointed out on the 3D surfaces has been implemented by a virtual sculpting approach. This development can be seen as a step towards custom made implants in the future.

The treatment of the medical images can be controlled by a medical doctor. The medical decisions are thus separated from the technical ones required for the actual manufacturing.

The technical data preparation has been speeded up. This implies interpolation to the layer thickness of the laser photopolymerisation process and contour based automatic support generation. Also the speed of the part building was drastically reduced during the project, from 30 hours to 5 hours for a specific part.
Both medical and technical software provide facilities to produce models with selectively coloured regions.

Low toxicity resin was developed to make medical models that can be used in the theatre room. They may even get in contact with the patient during the operation. Highly innovative is the development of a selectively colourable resin that fulfils the low toxicity requirement. This resin can also be used on the standard stereolithographic equipment currently installed.

Validation of the results has been performed on an technical and clinical level.

The accuracy of medical models is limited by the accuracy of the medical images and the equipment used for scanning. However, it is possible to overcome the resolution limitations of the scanner with intelligent interpolation approaches. For specific applications, accuracy up to a few tenths of a millimeter can be reached. This reasures that implants can be based on medical models.

The clinical validation in the Phidias project has been one of the first studies that goes beyond individual case reports. 30 surgeons from Belgium, France, Germany and the USA were contacted for the user requirements : 4 neurosurgeons, 7 maxillofacial surgeons , 2 traumatologists, 9 orthopaedic surgeons, 2 nose-ear-throat surgeons, 4 orthodontic and paradontic surgeons , 2 plastic and reconstructive surgeons. 25 of them have been using models for validation in the treatment of 48 patients.
The overall assesment of the models by 25 surgeons proves that the initial thesis of the project is true. Medical models help reconstructive surgeons to make their patients again resemble the ideal human being of the Greek sculptor Phidias.
Accurate, tangible models of the human bones and organs, based on medical images could greatly improve the quality of different kinds of surgical interventions due to the important additional information they offer compared to 2D scans or 3D displays. In addition they provide possibilities for planning of complex surgical procedures. The research in this project is targetted at the development of a dedicated system based on laser photopolymerisation for the production of medical models. Effort will be devoted to the following tasks:

- development of a scan mode on existing medical scanners to gather data with the accuracy needed for models;

- elaboration of software that enables control by the radiologist of data preparation for model building;

- development of low toxicity and colourable materials for the laser photopolymerisation process;

- adaptation of the laser photopolymerisation equipment for operation in a medical environment and for the production of coloured and bio-compatible models;

- requirement analysis and validation of the results of the project by task forces of surgeons from different specialisations.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

Materialise NV
Address
Technologielan 15
3001 Leuven
Belgium

Participants (3)

Imperial Chemical Industries plc (ICI)
United Kingdom
Address
The Heath
WA7 4QD Runcorn
KUL
Belgium
Address
Kardiaal Mercierlaan 94
3001 Heverlee
Siemens AG
Germany
Address
Henkestraße 127
91052 Erlangen