A comparative analysis of primate nasal airways using magnetic resonance imaging and nasal casts

The nasal cavity is an intricate part of the respiratory tract. It is not only the site of olfaction, but also serves as a filter to protect the lower respiratory tract from inhaled pollutants. A substantial fraction of inhaled particles deposit in this region and may pose potential health risks. To predict possible sites of inhaled aerosol deposition and better understand health risks associated with inhaled aerosols in this region, it is necessary to examine the morphometry of the nasal passage. Magnetic resonance imaging (MRI) of the nose was done from the anterior to the posterior, in 3-mm sections, on five anesthetized rhesus monkeys and on two nasal casts (one human and one rhesus monkey). The MRI images were analyzed for perimeter and cross-sectional areas of each section. Results indicated that the left and right nasal passages were very symmetric for the five monkeys but not for the human cast. The cross-sectional area and, consequently, the volume varied greatly among monkeys in vivo. Measurements from the monkey cast exhibited 1.4-fold differences normalized body weight in cross-sectional areas, but with smaller differences in perimeter when compared to the MRI in vivo images. The human cast exhibited a volume three times greater than that of the monkey cast, while the surface area was approximately doubled. Results from this comparison showed many similarities in the structure of the monkey and human nose suggesting that the rhesus monkey would be a good human surrogate in aerosol deposition studies.