Preliminary Volumetric Calculation of the Mucosal Surface in the Nares of Lambs Using a Segmentation of Computed Tomographic Images

Abstract

Intranasal vaccinations are becoming more important in both human and animal medicine to generate a localized IgA immune response not seen with parenteral vaccinations. This localized IgA response is more effective at reducing pathogen load on the mucosal surface of a potential host. One prerequisite for a successful nasal vaccination is the need to understand the distribution pattern of the nebulized vaccine, which requires an understanding the volume of the nares as well as the mucosal surface area. The exact mucosal surface area of ruminant nares has not yet been investigated. The aim of this concept study is to provide a detailed breakdown of a new method of volumetric rendering that can be used to calculate the volume and mucosal surface area of ruminant nares from computed tomographic images. The program Seg 3D was used to perform semi-automatic segmentation of a CT scan of a 9-month-old lamb head. Threshold segmentation and manual segmentation were used in combination to select the lamb's nasal cavity. The segmentation process yielded a volumetric rendering that was used to calculate the surface area and volume of the lamb's nasal cavity, with the segmentation process was repeated for each individual side of the lamb's nares. The surface area of the mucosal surface of each nostril is approximately 448 cm², and the volume is approximately 45 cm³. The methodology described in this study successfully calculated the volume and surface area of a lamb's nares using volumetric rendering.

Keywords: aerosol; mucosal surface; nasal volume; ruminant; vaccination.

Figure 1

(A) The volumetric rendering of the lamb's nares. Isoselesis (top left). Dorsoventral view (top right). Lateral view (bottom left). Rostrocaudal view (bottom right). Outliers are marked by a white circle. (B) Screen shot of the Seg 3D program with the isoselesis view of volumetric rendering in the center panel. The three tools used for the semi-automatic segmentation of the CT scan can be seen in the left panel. To the right of the central panel is the three imaging planes. The right-most panel shows the two final layers at this stage of the study. The layer “Crop_Threshold-1073.6TO-525.05_301” is highlighted and shows the surface area and volume of the volumetric rendering. The layer “301” is the initial CT scan that was used to create the segmentation layer visible in light green.

Figure 2

(A) Volumetric rendering of each side of the lamb's nares. The right side is in red. The left side is in blue. Isoselesis view (top left). Dorsoventral view (top right). Rostrocaudal view (bottom left). Ventrodorsal view (bottom right). Outliers are marked by a white circle. (B) Axial slide 241 with the right (red) and left (blue) sides of the lamb's nares selected (left). Volumetric rendering of the right and left nares with the CT scan planes visible for anatomical reference (right). (C) Screen shot of the Seg 3D program with the anteroposterior view of the volumetric rendering in the center panel. The three tools used for the semi-automatic segmentation can be seen in the left panel. To the right of the central panel is the three imaging planes. The right-most panel shows the “Right Side” layer (red) and the “Left Side” layer (blue). These two layers show the surface area and volume of their individual volumetric renderings.