Doppler optical coherence tomography monitoring of microvascular tissue response during photodynamic therapy in an animal model of Barrett's esophagus.
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.
Standish
Beau A
BA
Department of Medical Biophysics, University of Toronto, Ontario Cancer Institute, Toronto, Ontario, Canada.
Yang
Victor X D
VX
Munce
Nigel R
NR
Wong Kee Song
Louis-Michel
LM
Gardiner
Geoffrey
G
Lin
Annie
A
Mao
Youxin I
YI
Vitkin
Alex
A
Marcon
Norman E
NE
Wilson
Brian C
BC
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
D011166:Porphyrins