Impact of simulated light scatter on the quantitative, noninvasive assessment of retinal arteriolar hemodynamics
We determine the impact of artificial light scatter on quantitative, noninvasive assessment of retinal arteriolar hemodynamics. One eye from each of 10 healthy young subjects between the ages of 18 an...
Quantitative comparison of tissue oxygen and motexafin lutetium uptake by ex vivo and noninvasive in vivo techniques in patients with intraperitoneal carcinomatosis
Near-infrared diffuse reflectance spectroscopy (DRS) has been used to noninvasively monitor optical properties during photodynamic therapy (PDT). This technique has been extensively validated in tissu...
Interstitial Doppler optical coherence tomography monitors microvascular changes during photodynamic therapy in a Dunning prostate model under varying treatment conditions
J. Biomed. Opt., Vol. 12, 034022 (2007);
doi:10.1117/1.2744068
I. Alex Vitkin Ontario Cancer Institute, University of Toronto, Department of Medical Biophysics, Toronto, Ontario M5G 2M9, Canada and Ontario Cancer Institute, Radiation Oncology, Toronto, Ontario M5G 2M9, Canada
Victor X. D. Yang Ontario Cancer Institute, University of Toronto, Department of Medical Biophysics, Toronto, Ontario M5G 2M9, Canada and Ryerson University, Department of Physics, Toronto, Ontario M5B 2K3, Canada and Sunnybrook Health Science Center, Imaging Research, Toronto, Ontario M4N 3M5, Canada
We measure the tumor vascular response tovarying irradiance rates during photodynamic therapy (PDT) in a Dunningrat prostate model with interstitial Doppler optical coherence tomography (IS-DOCT).Rats are given a photosensitizer drug, Photofrin, and the tumorsare exposed to light (635 nm) with irradiance rates ranging from8 to 133 mW/cm2 for 25 min, corresponding to total irradiance of12 to 200 J/cm2 (measured at surface). The vascular index computedfrom IS-DOCT results shows the irradiance rate and total irradiancedependent microvascular shutdown in the tumor tissue during PDT. Whilefaster rates of vascular shutdown were associated with increasing PDTirradiance rate and total irradiance, a threshold effect was observedas irradiance rates above 66 mW/cm2 (surface), where no further increasein vascular shutdown rate was detected. The maximum post-treatment vascularshutdown (81%) without immediate microcirculatory recovery was reached with thePDT condition of 33 mW/cm2 and 50 J/cm2. Control groups without Photofrinshow no significant microvascular changes. Microvascular shutdown occurs at differentrates and shows correlation with PDT total irradiance and irradiancerates. These dependencies may play an important role in PDTtreatment planning, feedback control for treatment optimization, and post-treatment assessment.
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