Hyperbaric computed tomography: a novel tool to quantify the behavior of air-filled structures and gas emboli in cetacean and pinniped carcasses under a range of pressures

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TitleHyperbaric computed tomography: a novel tool to quantify the behavior of air-filled structures and gas emboli in cetacean and pinniped carcasses under a range of pressures
Publication TypeConference Paper
Year of Publication2009
AuthorsMoore, M., J. J. Arruda, S. R. Cramer, T. R. Hammar, D. R. Ketten, C. D. Moore, A. Fahlman, and S. E. Dennison
Conference Name18th Biennial Conference on the Biology of Marine Mammals
Date Published10/2009
PublisherSociety for Marine Mammology
Conference LocationQuebec, Canada
Keywordscetacean, gas emboli, hyperbaric chamber, pinniped, pressure
Abstract

The behavior of gas-filled compartments and bubbles in diving mammals has been a subject of modeling, some measurement, and much recent controversy. However, direct observation of how these volumes change with pressure has been limited. Accepting inevitable concerns about changes in tissue behavior post mortem, seal and dolphin cadavers can now be imaged under pressure using a radio-lucent, glass-fiber, water-filled pressure vessel rated to 250 psi. The combined mass of the sample and the vessel substantially exceed the weight limit of available CT scanner tables. Therefore, a custom rail and counterweighted carriage system were fabricated. The vessel is magnetically linked via an actuator on the CT table and a transponder on the vessel carriage to synchronize table and vessel movement. UHR-CT protocols were employed to image excised and in situ lungs, both in and out of the vessel. There was no loss of tissue detail or resolution for images in the pressure vessel. In this way the specimen can be spirally scanned within the chamber at a range of pressures. Quantification of the change in volume of the various gas-filled structures then allows an absolute measurement of the compliance of various critical structures. The resulting data will populate a new generation of mathematical models for determining how marine mammal lung tissues respond to pressure related gaseous changes in dissolved and gas phases during deep dives.