				Engineering for the Life Sciences Department of Engineering

Medical applications of optical motion capture

Our research involves the study of biological motion using multiple camera motion capture systems which reconstruct 3D models of the subject, using signal processing methodology. Optical motion capture is the art of turning the observations of a moving person (taken from a number of cameras) into 3D position and orientation information about that person. Such information can be used to better analyse a person's movements for medical reasons or sports performance, or could be used by virtual characters for film or computer games.

Using randomly placed markers (usually a minimal set - ie as few as you can get away with), we can construct an accurate skeleton of the subject: this is done via algorithms to extract centres of rotation of the joints. In order to track complex motion, it's necessary to have accurate models of the position of the markers relative to the joints of the skeleton (around which our limbs rotate). We have developed techniques which track slow moving (calibration) sequences and calculate the lengths, centres and axes of rotation of the limbs, and the relative 3D offsets of each marker on each limb. We are using this, in collaboration with hospitals, to help with a number of medical problems such as tracking the migration of hip replacements, choice and adjustment of prostheses and assessment of 3D shoulder alignment in post-stroke patients.

3D images of a person walking

We are also applying our research on optical motion capture, to try to understand how the brain controls motion and why certain motions are as they are. This includes looking at motor impaired individuals to see how and why this motion differs from the norm. This work is being carried out in collaboration with a number of physicians and physchologists.

This type of research has a number of applications and one other area we are examining is whether a 3D virtual environment can aid in the learning of hand-eye coordination skills (useful for those with certain types of disability as well as for sports men and women).

Contact: Dr Joan Lasenby, email: jl at eng.cam.ac.uk, tel: +44 1223 332806

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