Portable Laser Scanning Key to Biomechanical Research

Allosaurus in perspective with bones scanned by Polhemus FastSCAN from Virtalis

THE ROYAL Veterinary College (RVC) boasts one of the world’s biggest comparative motion research groups. Over the last year, the use of a portable, laser, digital CT scanner called the FastSCAN Cobra from Virtalis has transformed the way the researchers gather data. The RVC’s Structure and Motion Laboratory is headed up by Prof. Alan Wilson and carries out a wide range of research, including the prediction of lameness in both humans and animals and theoretical research into the gait of long extinct animals.

Dr. John Hutchinson, whose research is funded in part by the BBSRC, is reader in evolutionary biomechanics at the RVC. He explained: “Much of our work involves the use of dinosaur fossils and over the years we have Allosaurus front view with bones scanned by Polhemus FastSCAN from Virtalis used lots of different scanning and digitising systems,. About a year ago, a colleague recommended we try the FastSCAN and we’ve found that our research has broadened as a result. As it is portable, we have been able to travel with it and use it to scan rare fossils that would previously have been inaccessible to us. In addition, the quality of the scan data is excellent and the better the scan data, the better the quality of our reconstructions.”

The methods that Dr. Hutchinson and his team use were validated when, in earlier research, he reconstructed an ostrich body from its skeleton and then compared the estimated dimensions to empirically measured values from the original carcass. The team has since more broadly applied this validation to 3D scans of a wide variety of other animals, from birds to crocodiles and even elephants. Once the method was supported, the team moved on to extinct animals. This led to the revelation in 2007 that Tyrannosaurus rex was a significantly slower runner and turner than it had been assumed to be by most experts.

“Once the skeleton has been digitised by the FastSCAN, we are able to visualise it as a model on a PC”, said Dr. Hutchinson. “Next, a B-spline solid is fitted to enclose these points. Specialist software then builds the body segments. As the shape changes, the resulting changes in segment mass, centre of mass and moments of inertia can be recomputed instantly. Finally, we adjust the densities of the body, so that lungs, which are really void spaces, have different density values from bones. In this way, we have been able to show that the T.rex had a bigger tail than had originally been thought and that it had to bend its legs a bit rather than keep them pillar-straight to stand still, walk, or run. These factors meant that it was able to turn through 45o in between one to two seconds and could run no faster than between 10 and 25 miles per hour.”

Right femur of an Alligator scanned by Polhemus FastSCAN from Virtalis A colleague of Dr. Hutchinson in the RVC’s Structure and Motion Lab is using the FastSCAN in a similar way to determine the aerodynamic principles behind flapping flight. In Wellcome-funded research Dr. Jim Usherwood is measuring the aerodynamic properties of pigeon wings. “By using FastSCAN”, he commented, “I can precisely record the camber and twist along the entire length of the wing, so wing structure can be related to aerodynamic performance. This opens up the potential for creating physical models – ‘rapid prototypes’ – of pigeon wings with altered camber and twist, allowing systematic ‘what-if’ experiments. These models could be of use in other areas of research, as the fact we have models rather than numbers could feed into, for example, designs for a flapping micro vehicle.”