Collaborative Research: Reconstructing Airflow in the Nasal Cavity of Mammals

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The mammalian nose houses a complex set of paper-thin bones known as turbinals. Turbinals are involved in both the sense of smell and conditioning inspired air, and yet their function is not well understood. This is true despite the fact that a better knowledge of nasal anatomy and function is essential for progress in predicting particulate deposition in human airways, improving intranasal drug delivery, and the development of artificial sniffers for the detection of dangerous substances such as explosives. Some of the most important questions about turbinal function concern aspects of airflow through the nose. How do they direct air to the olfactory region? Are there separate pathways for respiration and olfaction? What can differences among species in the architecture of the turbinals tell us about the efficiency of odorant reception and heat and water conservation? To answer these questions, this project brings together scientists from two disparate fields, biology and engineering, to advance our understanding of respiration and olfaction. By combining modern high-resolution medical imaging, state-of-the-art models of flow, and data on nasal soft tissue distribution, this cross-disciplinary collaboration will be the first to apply novel computational modeling tools (e.g., 3-D anatomical reconstruction, computational fluid dynamics [CFD]) and experimental measurement techniques (e.g., use of anatomically-correct transparent physical models) to develop new form-function relationships for the nose. To do so, the 3-D nasal anatomy of five mammal species will be reconstructed from magnetic resonance images (MRI) of intact heads, computed tomography (CT) scans of their bony turbinals, and laboratory analysis of the distribution of olfactory vs. respiratory tissue. To enable future studies, paired sets of MRI scans of intact heads and CT scans of the cleaned skulls will be used to develop a method that corrects CT-derived image data of dry skull specimens for the absence of nasal mucosa. This will permit the study of nasal airflow using existing museum collections of skulls alone rather than intact heads, thereby greatly expanding the range of species and function that can be studied. Finally, to increase knowledge of nasal function beyond the two relatively short-snouted groups that have received the most attention, viz., primates and carnivores, the turbinals of 10-15 ungulate species will be reconstructed from CT scans of dry skulls and analyzed for turbinal dimensions. Over 10,000 CT slices of the skulls of 11-16 species of mammals, as well as paired sets of MRI scans of intact heads and CT scans of skulls for three individual mammals will be generated. All new scans will be deposited in the NSF Digital Morphology Library at the University of Texas, Austin (www.digimorph.org) for public access within 5 years of receiving funding for this project. Similarly, all of the numerical CFD models developed during this study will be made available via a website to be established by the PIs and hosted by Penn State University. Numerous graduate students and undergraduates will be trained in aspects of both biology and engineering as part of this project. Minority graduate and undergraduate students will be recruited through dedicated programs at each institution, and the investigators will continue their ongoing outreach efforts to high school students and lay audiences.