This award is for the development of instrumentation for 3D visualization of rapid skeletal motion in vertebrates. Its two primary components are (1) a high-speed, biplane X-ray fluoroscopy system and (2) automated software for precise, 3D skeletal animation by aligning 3D CT bone models with pairs of 2D X-ray images. The result will be a substantial advance over technology that is currently available for research in vertebrate functional morphology and biomechanics. The objective is to make dynamic 3D skeletal imaging an affordable and widely available technique. The new combination of high-speed, biplane X-ray and 3D visualization software is named "CTX imaging." Vertebrate functional morphology is an active and growing subfield of organismal biology in which the mechanical and evolutionary relationships between anatomical form and biomechanical function are investigated. For example, the action of long tendons as springs in kangaroo hopping, the effect of mouth size and shape on suction feeding in fish, and the function of the "wishbone" in bird flight have all been explained in the past two decades by functional morphologists. New discoveries in functional morphology have consistently been driven by the introduction of new technologies, such as high-speed cameras, electromyography, force plates and digital particle image velocimetry. Natural movements in animals almost always occur in 3D and often are very fast. Quantification of rapid skeletal movement in 3D would be a powerful technique for relating form to function, but functional morphologists have had no technique for measuring bone movements in 3D. The movement of external markers on the skin is generally used as a proxy for skeletal movement, but skin is often loose and the markers do not track the skeleton well. CTX analysis of a CT scan plus two X-ray movies will produce a highly accurate 3D animation of skeletal elements moving in space. These will be more than stick figures -- the complete 3D morphology of each bone will be present and animated precisely with this technique. Biplane X-ray imaging and CTX analysis will make it possible to study aspects of skeletal kinematics that are largely inaccessible with other techniques, such as long axis rotation of bones, putative bending of fine bones in small animals, and the relative 3D motions of the articular surfaces of joints. CTX will provide more accurate data for input into musculoskeletal models, such as joint angles for inverse dynamics and neural control models. This is an interdisciplinary proposal combining the expertise of two functional morphologists (Brainerd and Gatesy) who have extensive experience with dynamic X-ray imaging of animal movement and a computer scientist (Laidlaw) who specializes in building computational tools for accelerating science, with particular emphasis on scientific visualization tools.
Three-dimensional visualization of rapid skeletal motion in vertebrates will be possible with instrumentation to be developed under this award. CTX imaging, made possible with this instrumentation, will open up new areas of research in vertebrate functional morphology, such as the comparative study of 3D joint biomechanics. The animations developed with CTX will be powerful scientific tools, but they will also be accessible and appealing to the general public. These animations will be used to increase appreciation for basic research whenever possible.
