A means to accommodate residual limb movement during optical scanning: a technical note.

A technique is described for correcting for subject movement while imaging the residual limb of a person with a transtibial amputation. Small reflective markers were placed on the residual limb, and then their motions tracked during scanning using two stationary cameras. The marker position measurements were used to generate appropriate translational and rotational transformation matrices so that limb motion could be corrected for during the 1.5-s scan interval. Evaluation tests showed good performance for moderate (2-4 mm) to high (5-8 mm) motion cases. The difference in mean absolute cross-sectional area between the test scan and a stationary reference scan was reduced by approximately one half when motion correction was used compared with when motion correction was not used. The algorithm broke down for exaggerated motion ( >or= 9 mm) cases, particularly in areas outside the region encompassed by the markers. The developed method is useful in prosthetics research where high resolution shape measurement is needed, for example in cases where residual limb shape or volume change is of interest.