1. Department of Mathematical Sciences and Technology; Norwegian University of Life Sciences (NMBU); PO Box 5003, Drøbakveien 31, Ås, N-1432 Norway
2. Department of Biomedical Engineering; School of Medicine; King's College London Lambeth Wing, St. Thomas' Hospital, Westminster Bridge Road London SE1 7EH Great Britain
3. Department of Engineering Cybernetics; Norwegian University of Science and Technology (NTNU); Elektroblokk D, O.S Bragstads plass 2D, Trondheim Norway