Professor Stuart Bunt from the School of Anatomy, Physiol ogy and Human Biology at The University of Western Aus tralia leads a project examining the role of the carotid rete in drought adaptation of different sheep breeds. Sheep use the carotid rete as a counter current heat exchanger in a process known as selective brain cooling to delay evap orative heat loss and promote water retention, allowing them to survive for longer in dry conditions. Development of a larger carotid rete should allow for more efficient heat exchange and make the animal more suited to drier envi ronments. With his masters student Bradley Kinsella and help from NIF WA act ing node director A/Prof Matt Linden and NIF facility fellow Diana Engineer from the Centre for Microscopy, Chatacterisation and Anal ysis, Prof Bunt analyses the surface area of the rete us ing micro CT to determine the heat exchange efficien cy in the arid adapted Me rino and temperate adapt ed Suffolk. This information will help determine if there is any link between rete surface area and heat ex change efficiency.

Samples consist of blocks of bones containing the ca rotid rete injected with the iodine solution and imme diately scanned at 35┬Ám resolution on the Skyscan 1176 Micro CT. A relative ly high voltage and strong fil ter is required as the rete is completely surrounded by bone (an elec tron dense ma terial).

Scanned imag es were recon structed using the Feldkamp cone beam re construction algorithm with NRecon Soft ware. CTAn was used to calculate surface area and volume. The mean diameter and distance between rete vessels was determined by calculating the structure thickness and structure separation.