title: Doppler optical coherence tomography monitoring of microvascular tissue response during photodynamic therapy in an animal model of Barrett's esophagus.
abstract: BACKGROUND
  Doppler optical coherence tomography (DOCT) is an imaging modality that allows assessment of the microvascular response during photodynamic therapy (PDT) and may be a powerful tool for treatment monitoring/optimization in conditions such as Barrett's esophagus (BE).
  
  
  OBJECTIVE
  To assess the technical feasibility of catheter-based intraluminal DOCT for monitoring the microvascular response during endoluminal PDT in an animal model of BE.
  
  
  METHODS
  Thirteen female Sprague-Dawley rats underwent esophagojejunostomy to induce enteroesophageal reflux for 35 to 42 weeks and the formation of Barrett's mucosa. Of these, 9 received PDT by using the photosensitizer Photofrin (12.5 mg/kg intravenous), followed by 635-nm intraluminal light irradiation 24 hours after drug administration. The remaining 4 surgical rats underwent light irradiation without Photofrin (controls). Another group of 5 normal rats, without esophagojejunostomy, also received PDT. DOCT imaging of the esophagus by using a catheter-based probe (1.3-mm diameter) was performed before, during, and after light irradiation in all rats.
  
  
  RESULTS
  Distinct microstructural differences between normal squamous esophagus, BE, and the transition zone between the 2 tissues were observed on DOCT images. Similar submucosal microcirculatory effects (47%-73% vascular shutdown) were observed during PDT of normal esophagus and surgically induced BE. Controls displayed no significant microvascular changes.
  
  
  CONCLUSIONS
  No apparent difference was observed in the PDT-induced vascular response between normal rat esophagus and the BE rat model. Real-time monitoring of PDT-induced vascular changes by DOCT may be beneficial in optimizing PDT dosimetry in patients undergoing this therapy for BE and other conditions.
authors.affiliation: Department of Medical Biophysics, University of Toronto, Ontario Cancer Institute, Toronto, Ontario, Canada.
authors.forename: Beau A
authors.initials: BA
authors.lastname: Standish
authors.forename: Victor X D
authors.initials: VX
authors.lastname: Yang
authors.forename: Nigel R
authors.initials: NR
authors.lastname: Munce
authors.forename: Louis-Michel
authors.initials: LM
authors.lastname: Wong Kee Song
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Gardiner
authors.forename: Annie
authors.initials: A
authors.lastname: Lin
authors.forename: Youxin I
authors.initials: YI
authors.lastname: Mao
authors.forename: Alex
authors.initials: A
authors.lastname: Vitkin
authors.forename: Norman E
authors.initials: NE
authors.lastname: Marcon
authors.forename: Brian C
authors.initials: BC
authors.lastname: Wilson
mesh_terms: D000818:Animals; D001471:Barrett Esophagus / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000503:physiopathology; D001783:Blood Flow Velocity; D004947:Esophagus / Q000098:blood supply* / Q000000981:diagnostic imaging; D005260:Female; D008833:Microcirculation; D010778:Photochemotherapy; D011166:Porphyrins / Q000627:therapeutic use; D051381:Rats; D017207:Rats, Sprague-Dawley; D041623:Tomography, Optical Coherence / Q000379:methods; D018615:Ultrasonography, Doppler, Color
chemical_list: D011166:Porphyrins