cartome.org

19 August 2001

Australian Defence Science

No end to thermal imaging applications

Thermal imaging is proving to have wider and wider applications. DSTO's expertise in this area was even called on recently to help a giraffe in difficulty. Geoff Burls in Surveillance Systems Division was asked to help evaluate the status of the badly swollen right foreleg of twelve-year-old giraffe, Ketabi, at the Monarto open range zoo in South Australia. Using a commercially available thermal camera Mr Burls was able to assist the zoo's vet, Sue Conaghty, to identify the warmer zones on Ketabi's right leg compared with the other legs and the legs of other similar sized giraffes.

On different occasions the thermal imager was able to display the changes in temperature, and the increase and decrease in size of the higher temperature zones on the afflicted leg. Mr Burls, whose expertise is in electro-optic sensors, used an Inframetrics ThermaCAM SC1000, a hand held thermal imaging device that can receive the incoming three to five micrometre radiation from an object to provide thermal image of an object and its background.

He said that image processing within this device meant it was possible to view the scene in various ways including greyscale thermal and colour isothermal images. Scale bars at the side enable thermal differences to be gauged. The image signal could then be stored onto videotape or by digital means, and proprietary software enables post exercise thermal analysis. For the giraffe hoof evaluation, real time video image viewing, video recording and digital still frame recording procedures were used in the data gathering process.

The small size, light weight and portability of the camera enabled access to the more difficult viewing positions for imaging the giraffe's hoof. Mr Burls said the evaluation was not a simple case of viewing a thermal image generated by variations in temperature. During the process it was important to make sure the giraffe's hooves were totally in the shade or the sun at any one time as sun reflection can influence the band effects monitored by the detectors.

It was also necessary to compare the leg with similar zones on the other leg and other giraffes, and consider the different effects that a breeze, dust, mud, surface damage and hair may have on the thermal image and its interpretation. It was also necessary to consider the background and its temperature to ensure that a very hot background did not saturate the target image. The primary considerations of the thermal examination was the increase in temperature of the afflicted leg, the extent of the thermal changes along the leg, and then comparison of differences in temperature and the zones of that temperature compared to similar zones on other forelegs.

The afflicted leg appeared to be up to two degrees warmer than one without a problem, and extra warmth could be seen to extend further into the upper levels of the leg under examination. An increase in the temperature zone was noted during a short cessation of antibiotic and anti-inflammatory medication. Mr Burls said that thermal characteristics, and changes with time, were only a very small part of the many diagnostic considerations that were used by the vet to evaluate the extent of the injury and the zones of the leg that were being influenced by the swelling - which may have been due to infection, a bruise or fracture. Most importantly, it was a non-intrusive procedure.

Mr Burls said working with giraffes was the latest in a string of unusual challenges. He and other DSTO staff have also been called in to help monitor moths in cabbage patches and observe the after- dark habits of wombats.