Biomedical subjects

J D Schroeter

Publications and source records attributed to J D Schroeter.

3 recordsLinked to original sources

PubMed2001

Computer simulations of lung airway structures using data-driven surface modeling techniques.

Knowledge of human lung morphology is a subject critical to many areas of medicine. The visualization of lung structures naturally lends itself to computer graphics modeling due to the large number of airways involved and the complexities of the branching systems. In this study, a method of generating three-dimensional computer simulations of human lung airway networks using data-driven, surface modeling techniques is presented. By simulating the tubular airway structures and realistic bifurcation shapes, anatomically accurate representations of human lungs are obtained. These computer models are designed for use in computational fluid dynamic applications and particle trajectory analyses, and to be complimentary to medical imaging (gamma scintigraphy) protocols.

Computer Graphics↗

PubMed2001

Factors affecting the deposition of aerosolized insulin.

The inhalation of insulin for absorption into the bloodstream via the lung seems to be a promising technique for the treatment of diabetes mellitus. A fundamental issue to be resolved in the development of such insulin aerosol delivery systems is their efficiency (measured, for example, in terms of the amount of insulin absorbed in the blood compared to the total amount loaded into an inhalation device). A primary factor that could cause inefficiency of insulin absorption is deposition in the nonalveolated airways with subsequent removal from the lung via mucociliary clearance. Thus, a better understanding of the spatial distribution of insulin particle deposition in the lung can give guidance to the optimization of inhalation therapy. A mathematical model was used to study factors affecting the disposition of aerosolized insulin. The model calculates the trajectories of inhaled particles in the lung and has been validated by data from human subject experiments. Computer simulations were performed describing a wide range of patient breathing maneuvers. The results indicate significant variations in particle deposition patterns within lungs for different tidal volumes, inspiratory flow rates, and breath hold times. These findings indicate that particle sizes and ventilatory parameters are significant factors determining locations of particle deposition within human lungs, and thus the absorption of insulin into the blood stream via alveloated airways. Mathematical modeling is a valuable technique to complement clinical studies in the targeted delivery of inhaled insulin.

Administration, Inhalation↗

PubMed2000

Lung models: strengths and limitations.

The most widely used particle dosimetry models are those proposed by the National Council on Radiation Protection, International Commission for Radiological Protection, and the Netherlands National Institute of Public Health and the Environment (the RIVM model). Those models have inherent problems that may be regarded as serious drawbacks: for example, they are not physiologically realistic. They ignore the presence and commensurate effects of naturally occurring structural elements of lungs (eg, cartilaginous rings, carinal ridges), which have been demonstrated to affect the motion of inhaled air. Most importantly, the surface structures have been shown to influence the trajectories of inhaled particles transported by air streams. Thus, the model presented herein by Martonen et al may be perhaps the most appropriate for human lung dosimetry. In its present form, the model's major "strengths" are that it could be used for diverse purposes in medical research and practice, including: to target the delivery of drugs for diseases of the respiratory tract (eg, cystic fibrosis, asthma, bronchogenic carcinoma); to selectively deposit drugs for systemic distribution (eg, insulin); to design clinical studies; to interpret scintigraphy data from human subject exposures; to determine laboratory conditions for animal testing (ie, extrapolation modeling); and to aid in aerosolized drug delivery to children (pediatric medicine). Based on our research, we have found very good agreement between the predictions of our model and the experimental data of Heyder et al, and therefore advocate its use in the clinical arena. In closing, we would note that for the simulations reported herein the data entered into our computer program were the actual conditions of the Heyder et al experiments. However, the deposition model is more versatile and can simulate many aerosol therapy scenarios. For example, the core model has many computer subroutines that can be enlisted to simulate the effects of aerosol polydispersity, aerosol hygroscopicity, patient ventilation, patient lung morphology, patient age, and patient airway disease.

Aerosols↗