title: In vivo photoactivation without "light": use of Cherenkov radiation to overcome the penetration limit of light.
abstract: OBJECTIVE
  The poor tissue penetration of visible light has been a major barrier for optical imaging, photoactivatable conversions, and photodynamic therapy for in vivo targets with depths beyond 10 mm. In this report, as a proof-of-concept, we demonstrated that a positron emission tomography (PET) radiotracer, 2-deoxy-2-[(18)F]fluoro-D-glucose ((18)FDG), could be used as an alternative light source for photoactivation.
  
  
  METHODS
  We utilized (18)FDG, which is a metabolic activity-based PET probe, as a source of light to photoactivate caged luciferin in a breast cancer animal model expressing luciferase.
  
  
  RESULTS
  Bioluminescence produced from luciferin allowed for the real-time monitoring of Cherenkov radiation-promoted uncaging of the substrate.
  
  
  CONCLUSIONS
  The proposed method may provide a very important option for in vivo photoactivation, in particular for activation of photosensitizers for photodynamic therapy and eventually for combining radioisotope therapy and photodynamic therapy.
authors.affiliation: Molecular Imaging Laboratory, Department of Radiology, Massachusetts General Hospital/Harvard Medical School, Charlestown, MA 02129, USA.
authors.forename: Chongzhao
authors.initials: C
authors.lastname: Ran
authors.forename: Zhaoda
authors.initials: Z
authors.lastname: Zhang
authors.forename: Jacob
authors.initials: J
authors.lastname: Hooker
authors.forename: Anna
authors.initials: A
authors.lastname: Moore
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D002853:Chromatography, Liquid; D003952:Diagnostic Imaging / Q000379:methods*; D004601:Elementary Particles; D049454:Firefly Luciferin / Q000737:chemistry / Q000378:metabolism; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008027:Light; D008163:Luminescent Measurements; D013058:Mass Spectrometry; D051379:Mice; D008819:Mice, Nude; D012996:Solutions
chemical_list: D012996:Solutions; D019788:Fluorodeoxyglucose F18; D049454:Firefly Luciferin