Modelling of Brain Tissue Mechanical Properties: Motivation

Karol Miller

Mechanical properties of living tissues form a central subject in Biomechanics. The properties of the musculo-skeletal system, skin, lungs, blood and blood vessels have attracted much attention. The properties of "very" soft tissues, which do not bear mechanical loads, such as brain, liver, kidney, etc., have not been so thoroughly investigated.

However, recent developments in robotics technology, in particular the emergence of automatic surgical tools and robots [1] as well as advances in virtual reality techniques [2], call for closer examination of the mechanical properties of these tissues. This research was initially motivated by the need to design a Nuclear Magnetic Resonance Image guided surgical robot. NMRI can provide rich information of tissue deformation but currently tens of seconds are required to produce a set of images. The plausible method of dealing with these delays is the prediction of the deformation based on the model [3, 4], see also picture by K. Chinzei from MEL.

The appropriate "very" soft tissue models are required to equip the virtual reality surgeon training and operation planing systems with force and tactile feedback capabilities.

Knowledge of the mechanical properties of soft tissues and ultimately of their mathematical models is also required for registration: matching images of different modality, such as MRI and Single Photon Emission Computed Tomography (SPECT), defining relations between coordinate systems (eg., between a coordinate system associated with imaging equipment and those of robotic tools in an operating room), segmentation of reference features and defining disparity or similarity functions between extracted features [5]. Registration is a key technique for the computer-integrated surgery. Rigid tissue registration is now well-established. Registration of soft tissues is much more difficult because it requires the knowledge about local deformations. Here comes the place for accurate models of tissue deformation behaviour.

References:

1. Brett, P.N., Fraser, C.A., Henningan, M., Griffiths, M.V. and Kamel Y., Automatic Surgical Tools for Penetrating Flexible Tissues, IEEE Eng. Med. Biol., 1995, pp.264-270.

2. Burdea, G., Force and Touch Feedback for Virtual Reality. Wiley. New York, 1996.

3. Chinzei, K. and Miller, K., Modeling of Soft Tissues, Mechanical Engineering Laboratory News, 1995, 12, 5-7 (in Japanese).

4. Miller, K. and Chinzei, K., Modeling of Soft Tissues Deformation, Journal Computer Aided Surgery, 1995, 1, Supl., Proc. of Second International Symposium on Computer Aided Surgery, Tokyo Women's Medical College, Shinjuku, Tokyo, 62-63.

5. Lavallée, S., Registration for Computer Integrated Surgery: Methodology, State of the Art. Computer-Integrated Surgery, 1995, MIT Press, Cambridge Massachusetts, pp. 77-97.