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Proceedings Paper

Modeling the oxygen microheterogeneity of tumors for photodynamic therapy dosimetry
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Paper Abstract

Photodynamic theory of tumors uses optical excitation of a sensitizing drug within tissue to produce large deposits of singlet oxygen, which are thought to ultimately cause the tumor destruction. Predicting dose deposition of singlet oxygen in vivo is challenging because measurement of this species in vivo is not easily achieved. But it is possible to follow the concentration of oxygen in vivo, and so measuring the oxygen concentration transients during PDT may provide a viable method of estimating the delivered dose of singlet oxygen. However modeling the microscopic heterogeneity of the oxygen distribution within a tumor is non-trivial, and predicting the microscopic dose deposition requires further study, but this study present the framework and initial calibration needed or modeling oxygen transport in complex geometries. Computational modeling with finite elements provides a versatile structure within which oxygen diffusion and consumption can be modeled within realistic tissue geometries. This study develops the basic tools required to simulate a tumor region, and examines the role of (i) oxygen supply and consumption rates, (ii) inter- capillary spacing, (iii) photosensitizer distribution, and (iv) differences between simulated tumors and those derived directly from histology. The result of these calculations indicate that realistic tumor tissue capillary networks can be simulated using the finite element method, without excessive computational burden for 2D regions near 1 mm2, and 3D regions near 0.1mm3. These simulations can provide fundamental information about tissue and ways to implement appropriate oxygen measurements. These calculations suggest that photodynamic therapy produces the majority of singlet oxygen in and near the blood vessels, because these are the sites of highest oxygen tension. These calculations support the concept that tumor vascular regions are the major targets for PDT dose deposition.

Paper Details

Date Published: 29 March 2000
PDF: 9 pages
Proc. SPIE 3909, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy IX, (29 March 2000); doi: 10.1117/12.379892
Show Author Affiliations
Brian W. Pogue, Dartmouth College (United States)
Keith D. Paulsen, Dartmouth College (United States)
Julia A. O'Hara, Dartmouth Medical School (United States)
P. Jack Hoopes, Dartmouth Medical School (United States)
Harold Swartz, Dartmouth Medical School (United States)


Published in SPIE Proceedings Vol. 3909:
Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy IX
Thomas J. Dougherty, Editor(s)

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