PARENT SESSION
1:30 PM to 3:30 PM
Saturday, April 20, 2002
Poster Session 1 Noninvasive Treatment Monitoring and Treatment Planning
Room: Nevada 1-2
(MP01-8) Utility of optical sensors in monitoring interstitial laser photocoagulation.
Chin, Lee*,1,2, Whelan, William2,4, Sherar, Michael1,2,3, Vitkin, Alex1,2,3, 1 Ontario Cancer Institute / Princess Margaret Hospital University Health Network, Toronto, Ont.2 Department of Medical Biophysics, University of Toronto, Toronto, Ont.4 Ryerson Polytechnic University, Toronto, Ont.3 Department of Radiation Oncology, University of Toronto, Toronto, Ont.
ABSTRACT-
Interstitial laser photocoagulation (ILP) is a novel therapy that is currently under development for the treatment of solid tumors. Due to the complex and dynamic nature of tissue alterations occurring during ILP, the development of real-time monitoring systems that can accurately detect tissue changes during ILP and preserve critical normal structures is vital. Currently, temperature sensors offer a practical means by which to monitor and control ILP treatments. However, due to characteristically slow thermal conduction times, interspecies variability in thermal damage, and the inability to directly sense tissue coagulation, temperature measurements alone, might be insufficient for assessing treatment efficacy. Optical monitoring, where light intensity information is measured using interstitial optical sensors provides near instantaneous response to structural changes that occur during treatment. Our experiments in phantoms and ex-vivo tissue have demonstrated that optical monitoring is able to determine the onset of coagulation, occurrence of charring, and the location of the coagulation front as it passes the optical sensor. Theoretically, we are using a two region Monte Carlo simulation (of coagulated and native tissue) in both spherical and cylindrical geometry to assess the ability of radiance and fluence information in determining the boundary of tissue coagulation. Monte Carlo simulations and experimental data demonstrate that optical information, most notably radiance, is sensitive to changes in tissue structure due to coagulation, particularly as the coagulation front passes an optical sensor. However, to quickly determine the extent of coagulation at all other locations requires an appropriate analytical two-region light model of coagulated and native tissue. Currently, we are performing parametric studies against our Monte Carlo results using a two-region diffusion theory model of coagulated and native tissue to inversely predict the boundary of coagulation at all locations throughout the course of the ILP treatment.
KEYWORDS: optical monitoring, laser thermal therapy, fluence, radiance