Fluence rate as a modulator of PDT mechanisms.

Fluence rate as a modulator of PDT mechanisms. Research Abstract Details 

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Fluence rate as a modulator of PDT mechanisms. Abstract Text:

Barbara W Henderson,Theresa M Busch,John W Snyder,

BACKGROUND AND OBJECTIVES: Molecular oxygen in the tissue to be treated by photodynamic therapy (PDT) is critical for photodynamic cell killing. The fluence rate of PDT light delivery has been identified as an important modulator of tissue oxygenation and treatment outcome. This article provides supporting evidence for the role of fluence rate in PDT and discusses the underlying mechanisms. STUDY DESIGN/MATERIALS AND METHODS: Intratumoral pO2 was measured polarographically in murine tumors before and during PDT light treatment using the Eppendorf pO2 Histograph. Tumor response as a function of fluence rate and fluence was also assessed in murine tumor models. Changes in vascular permeability as a function of fluence rate were determined in murine tumors by measuring tumor uptake of fluorescent beads (200 nm diameter). RESULTS: Severe oxygen depletion is shown to occur within seconds of illumination at a fluence rate of 75 mW/cm2 in radiation-induced fibrosarcoma (RIF) tumors photosensitized with AlPcS2. This effect was reversible and consistent with photochemical oxygen depletion, which has been shown by us and others to be fluence rate dependent. It is demonstrated that fluence rate affects the PDT tumor response in the Colon 26 tumor model, high fluence rate diminishing or even totally inhibiting tumor control, low fluence rate promoting tumor control. The influence of fluence rate is not restricted to cytocidal effects, but can also be seen in sublethal conditions such as vascular permeability. CONCLUSIONS: Fluence rate of PDT light delivery exerts far-reaching control upon treatment outcome through its oxygenation modulating properties and possibly other mechanisms yet to be identified. This has been shown to be true in the preclinical and clinical setting. Further development of in situ dosimetry will be necessary to take full advantage of these discoveries.

Fluence rate as a modulator of PDT mechanisms. Publishing Authors By Initials

BW Henderson,TM Busch,JW Snyder,

For similar chemical actions and uses: pharmacologic actions: physiological effects of drugs: radiation-sensitizing agents: photosensitizing agents research abstracts see: chemical actions and uses: pharmacologic actions: physiological effects of drugs: radiation-sensitizing agents: photosensitizing agents research

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Fluence rate as a modulator of PDT mechanisms. Journal Published:

PUBLICATION TYPE: Review

Journal: Lasers in surgery and medicine

VOLUME: 38

Page Numbers: 489-93

Journal Abbreviation:

ISSN: 0196-8092

DAY: 3

MONTH: Jun

YEAR: 2006

Fluence rate as a modulator of PDT mechanisms. Information

Number of References: 26

LANGUAGE: eng

NlmUniqueID: 8007168

Fluence rate as a modulator of PDT mechanisms. Keywords Mesh Terms:

KEYWORDS: Photosensitizing Agents

MESH TERMS: pharmacology

Chemical & Substance for Abstract: Fluence rate as a modulator of PDT mechanisms. Information

Substance Name: Oxygen

Registry Number: 7782-44-7

Grant and Affiliation Information for Fluence rate as a modulator of PDT mechanisms.

AFFILIATION: Department of Cell Stress Biology, The Photodynamic Therapy Center, Roswell Park Cancer Institute, Buffalo, New York, New York 14263, USA. barbara.henderson@roswellpark.org

Country: United States

AGENCY: United States NCI

GRANT: CA55791

ACRONYM: CA

MEDLINETA: Lasers Surg Med

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