X-RAY KINEMATOGRAPHY AS A TOOL FOR INVESTIGATIONS OF DISTAL LIMB MOVEMENTS OF THE CAT

X-ray kinematography was used to investigate the kinematics of cat dis tal forelimb joints during motor behaviour. These joints are not acces sible for instrumentation with external markers normally used in conve ntional motion analysis systems. To trace the movements in space two X -ray systems positioned rectangularly to each other illuminated the fo relimb quasi-simultaneously with pulsed X-ray shots (time resolution: 20 ms). A mathematical model was developed for 3-dimensional reconstru ction of the object and includes procedures for correction of image di stortions, e.g., pincushion distortions and rotation of the image due to interaction of the earth's magnetic field with the electron optics of the image amplifiers. Accuracy of image correction and object recon struction is +/-1 pixel, corresponding to +/-0.5 mm in space which is sufficient for investigation of the kinematics of cat distal forelimb joints. The approach described is of general relevance and useful in k inematic investigations where the structures under study are not direc tly accessible to external instrumentation with markers.