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2006 Progress Report: Project 5 -- Architecture Development and Particle Deposition

EPA Grant Number: R832414C005
Subproject: this is subproject number 005 , established and managed by the Center Director under grant R832414
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
Center: San Joaquin Valley Aerosol Health Effects Research Center (SAHERC)
Center Director: Wexler, Anthony S.
Title: Project 5 -- Architecture Development and Particle Deposition
Investigators: Wexler, Anthony S. , Plopper, Charles
Current Investigators: Wexler, Anthony S. , Schelegle, Ed
Institution: University of California - Davis
EPA Project Officer: Stacey Katz/Gail Robarge,
Project Period: October 1, 2005 through September 30, 2010
Project Period Covered by this Report: October 1, 2005 through September 30, 2006
RFA: Particulate Matter Research Centers (2004)
Research Category: Particulate Matter

Description:

Objective:

The objective is to develop the tools necessary to quantify lung architecture.

Progress Summary:

Two current activities are highlighted below, acquisition of CT image data, and second, characterization of pulmonary architecture.

Acquisition of CT Image Data

A custom designed micro CT scanner was used to obtain voxel image of the lung casts. In this system, the CMOS detector with an active area of 50 × 100 mm2 and 48 μm pixel size produces 1024 × 2048 projection images with 12-bit digital resolution. A rotary stage driven by a stepping motor was used to rotate the lung specimens. To avoid motion artifacts of the cast during stage rotation, the cast was fixed in a block of paraffin wax. The 3D CT data set was reconstructed from 1000 projections with a custom developed cone beam reconstruction program using Feldkamp-Davis-Kress (FDK) algorithm. The 3D data set was reconstructed as a 512×512×300 array with corresponding pixel size of 79.4×79.4×86.6 μm3 to cover most of rat airways. A sample of projection image is shown in Figure 1.

Figure 1. CT Image in Axial View (Left) and Sagittal View (Right)
Figure 1. CT Image in Axial View (Left) and Sagittal View (Right)

Characterization of Pulmonary Architecture

We developed a new algorithm to quantify the branching structure of the pulmonary tree. A general mathematical bifurcation model was developed first that duplicates airway geometry. We used 9 independent geometric parameters to characterize bifurcation geometry. By varying the combination of these geometry parameters various bifurcation shapes can be duplicated. Using the flexible bifurcation model, parameter set that minimizes error between real lung airway (CT image data) and bifurcation model is searched at each airway, extracting key geometric information of pulmonary airways (Figure 2). This optimization problem is of large scale and one where a desired global minimum is hidden among many, poor, local minima. The simulated annealing method, known to be suitable for this kind of problem, is adopted to find the best fit. This algorithm was able to successfully analyze airways as small as branch radius is equal to 2 times pixel. The algorithm was validated by error analysis and comparison of statistical results obtained by comparing our technique with previous anatomy studies of rat lung (Phillips 1995, Sera 2003).

Figure 2. Demonstration of Characterization of Pulmonary Architecture (Dark Areas are Computer Model Predicted Fits to the Voxel Data; Light Areas are Voxelated Data From Rat Lung Casts)
Figure 2. Demonstration of Characterization of Pulmonary Architecture (Dark Areas are Computer Model Predicted Fits to the Voxel Data; Light Areas are Voxelated Data From Rat Lung Casts)

Future Activities:

The advantage of our technique is that it can perform quantitative error analysis along with characterization of pulmonary architecture. We will continue to improve the algorithm so as to clearly distinguish erroneous data from reliable results. In addition we will try various optimization subroutines to reduce computer analysis time.

References:

Phillips CG, Kaye SR. Diameter-based analysis of the bronchial geometry of four mammalian bronchial trees. Respiration Physiology 1995;102:303-316.

Sera T, Fujioka H, Yokota H, Makinouchi A, Himeno R, Schroter RC, Tanishita K. Three-dimensional visualization and morphometry of small airways from microfocal X-ray computed tomography. Journal of Biomechanics 2003;36:1587-1594.

Journal Articles:

No journal articles submitted with this report: View all 5 publications for this subproject

Supplemental Keywords:

 , ENVIRONMENTAL MANAGEMENT, Air, Scientific Discipline, Health, RFA, PHYSICAL ASPECTS, Risk Assessment, Risk Assessments, Health Risk Assessment, Physical Processes, Biochemistry, particulate matter, Environmental Chemistry, exposure assessment, cardiovascular disease, chemical characteristics, particulate matter components, children's health, cardiopulmonary responses, human health risk, acute cardiovascular effects, human health effects, toxicology, particle deposition, atmospheric particulate matter, exposure, airborne particulate matter, human exposure, PM, animal model
Relevant Websites:

http://saherc.ucdavis.edu/ exit EPA

Progress and Final Reports:
Original Abstract
2007 Progress Report
2008 Progress Report


Main Center Abstract and Reports:
R832414    San Joaquin Valley Aerosol Health Effects Research Center (SAHERC)

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R832414C001 Project 1 -- Pulmonary Metabolic Response
R832414C002 Endothelial Cell Responses to PM—In Vitro and In Vivo
R832414C003 Project 3 -- Inhalation Exposure Assessment of San Joaquin Valley Aerosol
R832414C004 Project 4 -- Transport and Fate Particles
R832414C005 Project 5 -- Architecture Development and Particle Deposition

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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