Document Detail

Oxygen consumption and diffusion effects in photodynamic therapy.
MedLine Citation:
PMID:  2034787     Owner:  NLM     Status:  MEDLINE    
Effects of oxygen consumption in photodynamic therapy (PDT) are considered theoretically and experimentally. A mathematical model of the Type II mechanism of photooxidation is used to compute estimates of the rate of therapy-dependent in vivo oxygen depletion resulting from reactions of singlet oxygen (1O2) with intracellular substrate. Calculations indicate that PDT carried out at incident light intensities of 50 mW/cm2 may consume 3O2 at rates as high as 6-9 microM s-1. An approximate model of oxygen diffusion shows that these consumption rates are large enough to decrease the radius of oxygenated cells around an isolated capillary. Thus, during photoirradiation, cells sufficiently remote from the capillary wall may reside at oxygen tensions that are low enough to preclude or minimize 1O2-mediated damage. This effect is more pronounced at higher power densities and accounts for an enhanced therapeutic response in tumors treated with 360 J/cm2 delivered at 50 mW/cm2 compared to the same light dose delivered at 200 mW/cm2. The analysis further suggests that the oxygen depletion could be partially overcome by fractionating the light delivery. In a transplanted mammary tumor model, a regimen of 30-s exposures followed by 30-s dark periods produced significantly longer delays in tumor growth when compared to the continuous delivery of the same total fluence.
T H Foster; R S Murant; R G Bryant; R S Knox; S L Gibson; R Hilf
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Radiation research     Volume:  126     ISSN:  0033-7587     ISO Abbreviation:  Radiat. Res.     Publication Date:  1991 Jun 
Date Detail:
Created Date:  1991-06-24     Completed Date:  1991-06-24     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0401245     Medline TA:  Radiat Res     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  296-303     Citation Subset:  IM; S    
University of Rochester School of Medicine and Dentistry, Department of Radiology, New York 14642.
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MeSH Terms
Mammary Neoplasms, Experimental / drug therapy,  metabolism,  pathology
Models, Chemical
Oxygen Consumption / physiology*
Rats, Inbred F344
Grant Support

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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