Author: Victoria Susan Ainsworth, Wilfred F. Ngwa, Erno Sajo 👨🔬
Affiliation: University of Massachusetts Lowell, Johns Hopkins University 🌍
Purpose: In nanoparticle-enhanced radiotherapy, the dose enhancement is function of the particle size. At therapeutic concentrations, the number density of nanoparticles gives rise to a high rate of interparticle collision, which leads to non-negligible agglomeration. Therefore, for inhalation-based nanoparticle enhanced radiotherapy, it is important to determine the size distribution of deposited nanoparticle agglomerates within the lung.
Methods:
In our previous study, we validated the aerosol dynamics simulation computer code SAEROSA against in-vivo experiments within a generational model of the whole lung using surrogate Styrofoam nanoparticles in low initial concentrations. The transitional steps from validation to therapeutic loads of gold nanoparticles were also reported, with a focus on bulk deposition fractions for each airway generation and connected alveoli. However, because the particle size is correlated with its capacity for dose enhancement, the deposited particle size distribution (as opposed to bulk deposition) is important information for dose assessment. In this work, we explore the size distribution of deposited gold nanoparticle agglomerates in up to 23 generations.
Results:
At high initial inhalation concentrations, which is necessary to achieve therapeutic concentrations of deposited particles in the lung, agglomeration occurs almost immediately as the inhalation begins. The size distribution of airborne particles dynamically changes in the lung from generation to generation. Consequently, the deposition pattern of clustered particles shows significant differences in various generations, airways and alveoli, creating important ramifications for treatment planning considerations. Size distributions between gold and other materials are also different despite having similar bulk deposition patterns.
Conclusion: Coagulation has an important effect on nanoparticle deposition within the lung, which leads to important treatment planning considerations. Our computations show that particles can agglomerate into clusters up to 32 particles.