title: Local physiological changes during photodynamic therapy.
abstract: OBJECTIVE
  Herein an overview is provided of the causes, consequences, and significance of photodynamic therapy (PDT)-mediated effects on tumor oxygenation and blood flow during illumination.
  
  
  METHODS
  Techniques particularly valuable to this research have included tissue oxygen tension measurement by the Eppendorf pO2 Histograph; spatial quantification of hypoxia by EF3 and EF5; and tissue oxygenation/blood flow monitoring by diffuse reflectance/correlation spectroscopy.
  
  
  RESULTS
  Severe hypoxia was measured in vivo during PDT and is shown to be a consequence of photochemical oxygen consumption and/or compromised vascular perfusion. Oxygen depletion can be controlled by treatment regimen, occurs in a spatially-definable pattern, and is therapy-limiting. PDT-induced changes in tumor oxygenation during illumination are correlated with outcome. In PDT-treated tissues, blood flow also is determined by treatment regimen and correlates with treatment response.
  
  
  CONCLUSIONS
  Photodynamic therapy creates distinct, measurable changes in tumor oxygen and blood flow during illumination. These physiological changes may ultimately affect treatment efficacy.
authors.affiliation: Department of Radiation Oncology, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6072, USA. buschtm@mail.med.upenn.edu
authors.forename: Theresa M
authors.initials: TM
authors.lastname: Busch
mesh_terms: D000818:Animals; D000860:Hypoxia / Q000378:metabolism; D009369:Neoplasms / Q000098:blood supply* / Q000378:metabolism*; D010101:Oxygen Consumption; D010778:Photochemotherapy; D017382:Reactive Oxygen Species / Q000378:metabolism; D012039:Regional Blood Flow
chemical_list: D017382:Reactive Oxygen Species