Fast translation of CT scan data into complete 3D models for FEA

Using Materialise’ 3D image processing and editing software Mimics, the research team processed CT scan data of the foot region of a 26 year old male. After importing the medical data (DICOM images), the team employed a thresholding technique based on Hounsfield units to separate the bone and the soft tissues. They manually separated the segmentation mask for each bone with the region growing tool. As a result, every bone now corresponds to an individual mask, which can be distinguished by the different applied mask colors. This process allows the generation of independent geometrical files and 3D models. For the complete definition of the bone foot structure and soft tissues, 30 different regions were defined in no time. The foot was then reconstructed in 3D with Mimics, capturing each bone and the encapsulated soft tissues volume that geometrically define the foot structure.
In order to create 3D CAD models, each model was exported to an STL-file. Using CATIA software, the cartilages that were not reconstructed in the segmentation process were then modeled, and volume Boolean operations were performed to achieve a volume of soft tissues. This procedure guaranteed optimal alignment of the cartilages on the bones, an important consideration for future finite element model generation.
 
Next, the researchers imported the assembled model of the foot’s bone structure, the modeled cartilage and the Boolean-generated soft tissues volume in the non-linear FEA package Abaqus. The model was then prepared for non-linear analysis, achieved specifically through the definition of loads, boundary conditions, material properties, kinematic constraints and mesh discretization processes. The resulting FEA model allows the output of several variables that can be used to evaluate the comfort of shoe insoles or to study other biomechanical aspects of the foot, such as Von Mises stress or plantar contact pressure.
 
The FEA plantar contact pressure values were experimentally verified by the use of equipment that measures podologic pressures. The non-linear FEA model generated in this study can serve as a tool for design optimization of shoe insoles or other foot support devices. With this model, a wide variety of insole geometries and materials can be tested in order to study and improve foot comfort. This can be achieved by modifying the insole’s geometrical design and/or the formulation of the insole’s materials.

Mimics has again proven to be an invaluable tool in creating an accurate, detailed and anatomically correct 3D model based on scanner data. Mimics’ ability to generate perfect patient-specific meshes and to export them to any FEA package, make it the tool of choice for biomechanical research. Its user-friendliness and high performance design lift every project to a higher level.

 

Regulatory Information:
Mimics Innovation Suite currently consists of the following medical device software components: Mimics version 15 and 3-matic version 7 (released 2012). Mimics is intended for use as a software interface and image segmentation system for the transfer of imaging information from a medical scanner such as a CT scanner or a Magnetic Resonance Imaging scanner. It is also used as pre-operative software for simulating /evaluating surgical treatment options. 3-matic is intended for use as software for computer assisted design and manufacturing of medical exo- and endo-prostheses, patient specific medical and dental/orthodontic accessories and dental restorations.


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jpg_CE-0120.jpgMimics is a CE-marked product. Copyright 2012 Materialise N.V – L -10032 revision 1, 12/2012
Materialise has the appropriate regulatory registrations in Europe and the United States