Total Dosimetry Research Articles

Leveraging statistical shape modeling in computational respiratory dynamics: Nanomedicine delivery in remodeled airways

Background and ObjectiveAccurate knowledge of the delivered doses to the diseased site in the respiratory tract is crucial to elicit desired therapeutic outcomes. However, such information is still difficult to obtain due to inaccessibility for measurement or visualization, complex network structure, and challenges in reconstructing lung geometries with disease-invoked airway remodeling. This study presents a novel method to simulate the airway remodeling in a mouth-lung geometry extending to G9. MethodsStatistical shape modeling was used to extract morphological features from a lung geometry database and four new models (i.e., M1-M4) were generated with parameter-controlled dilated/constricted bronchioles in the left-lower (LL) lung. The variations in airflow and particle deposition due to the airway remodeling were simulated using a well-tested k-ω turbulence model and a Lagrangian tracking approach. ResultsSignificant variations in flow partitions between the lower and upper lobes of the left lung, as well as between the left and right lungs. The flow partition into the LL lobe varied by 10-fold between the most dilated and constricted models in this study. Significantly lower doses were also predicted on the surface of the constricted LL bronchioles G4-G9, as well as into the peripheral airways beyond G9. However, the total dosimetry in the mouth-lung geometry (up to G9) exhibited low sensitivity to the LL lobar remodeling. Results in this study suggest that the optimal nanomedicine should be 2–10 nm in diameter if targeted at the constricted bronchioles G4-G9 as in topical inhalation therapy but should be larger than 20 nm if targeted at the alveolar region as in systemic therapy. ConclusionsThis study highlights the large dose variability from local airway remodeling and the need to consider these variations in the treatment planning for pneumonia and other obstructive respiratory diseases.

Inhalation dosimetry of nasally inhaled respiratory aerosols in the human respiratory tract with locally remodeled conducting lungs

Objective: Respiratory diseases are often accompanied by alterations to airway morphology. However, inhalation dosimetry data in remodeled airways are scarce due to the challenges in reconstructing diseased respiratory morphologies. This study aims to study the airway remodeling effects on the inhalation dosimetry of nasally inhaled nanoparticles in a nose–lung geometry that extends to G9 (ninth generation). Materials and methods: Statistical shape modeling was used to develop four diseased lung models with varying levels of bronchiolar dilation/constriction in the left-lower (LL) lobe (i.e. M1–M4). Respiratory airflow and particle deposition were simulated using a low Reynolds number k–ω turbulence model and a Lagrangian tracking approach. Results: Significant discrepancies were observed in the flow partitions between the left and right lungs, as well as between the lower and upper lobes of the left lung, which changed by 10-fold between the most dilated and constricted models.Much lower doses were predicted on the surface of the constricted LL bronchioles G4–G9, as well as into the peripheral airways beyond G9 of the LL lung. However, the LL lobar remodeling had little effect on the dosimetry in the nasopharynx, as well as on the total dosimetry in the nose–lung geometry (up to G9). Conclusion: It is suggested that airway remodeling may pose a higher viral infection risk to the host by redistributing the inhaled viruses to healthy lung lobes. Airway remodeling effects should also be considered in the treatment planning of inhalation therapies, not only because of the dosimetry variation from altered lung morphology but also its evolution as the disease progresses.

Investigations of the effects of cosmic rays on Artemia cysts and tobacco seeds; results of Exobloc II experiment, flown aboard Biocosmos 1887.

Artemia (Brine shrimp) cysts and tobacco seeds, dormant biological material devoid of metabolic activity, were flown aboard the Soviet Biocosmos 1887 in order to investigate the effects of cosmic rays. Artemia cysts and tobacco seeds were used in bulk or in monolayers sandwiched with track detectors. Biological and physical units were located outside and inside the spacecraft. Stacks included lead shielding in order to expose the objects to different doses of radiation. Total dosimetry was performed using thermoluminescent detectors. In spite of low levels of doses, the space flight resulted in a decrease in developmental capacity of Artemia cysts, and in a higher mutation rate in tobacco seeds. The more obvious responses occurred, in both cases, in biological objects exposed to the highest doses. These results are compared to those of previous space experiments.