Modeling Deposition of Inhaled Particles - Aerosols: Measurement, Dosimetry, and Health Effects - page 105

10 -1

6.7 µm (Martonen, 1983) 7.1 µm (Schlesinger et al., 1977)

2.5 µm (Schlesinger et al., 1977) 1.9 µm (Martonen, 1983)

10 -2

10 -3

1 2 3 4 5 6

Tracheobronchial generation

FIGURE 5.9 Deposition of particles in the TB region as measured by Martonen 254 using a silicone rubber
cast, compared with the replica cast data of Schlesinger et al., 256 for different particle sizes.

in realistic geometries. In addition, deposition studies in casts can be reproduced, and particles
of different sizes and characteristics may be studied serially under the same conditions. Replica
cast studies have been performed in the human TB region, 26,251-253 in canine lungs, 252 and in nasal
passages. 254,255 Other studies have been performed using laryngeal casts combined with a silicone
rubber model of the TB airways. 256,257 Deposition data obtained in this silicone model at a low
rate of 15 L/min are shown in Figure 5.9 for two particle sizes. Deposition in a TB replica cast 258 is
also shown. In this igure, the ratio of the amount of aerosol deposited in a single generation to the
amount entering the cast is plotted. Note that good agreement between the replica cast and the sili-
cone model results were obtained. Table 5.3 summarizes localized (i.e., bifurcation) deposition from
the two silicone model studies for several particle sizes at three different low rates. Speciically, the
table contains the bifurcation deposition ratio B d , where

B d = (

) ( )

⎣ aerosol mass deposited within a bifurcation / bifurcation surface area ⎦

⎣

÷ total aerosol mass deposited within the two airwa ys of a generation ,

) ( ) ⎦ (5.9)

including the shared bifurcation / total ai rway and bifurcation surface area

Note that in most cases, the deposition in the bifurcation zone is enhanced in relation to the adjacent
airways. For example, at a low rate of 60 L/min the deposition of 8.7 μm particles at the third gen-
eration bifurcation is three times greater than that in the adjacent airway segments. The values of
B d of less than 1 may be due to large regions of the bifurcations site having 0 deposition, as observed
by Schlesinger et al. 251
Recently, advances in stereolithography and “3D printing” techniques have allowed for the rapid
development of plastic (resin) or polymer models from medical images for use in deposition studies.
Such models include the Premature Infant Nose Throat (PrINT) model, 259 an MRI-based polymer
model, and the Sophia Anatomical Infant Nose-Throat model. 260 In addition, Giesel et al. 261 pre-
sented a method of rapidly prototyping models of the upper (generations 0-5) TB airways using CT
scanning and laser sintering.