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11 October 2013 Analyzing effects of temperature on tissue equivalent phantoms using fiber Bragg gratings and optical coherence tomography
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Proceedings Volume 8915, Photonics North 2013; 891504 (2013)
Event: Photonics North 2013, 2013, Ottawa, Canada
There exist a multitude of therapeutic options for the treatment of both benign and malignant tumors, where several of these options induce temperature changes in the tissue from several degrees centigrade to temperatures that ablate the region of interest (ROI). Recent advances in optical imaging technologies, namely optical coherence tomography (OCT) and Fiber Bragg Gratings (FBG), may provide the necessary hardware/software components to both monitor and quantify the direct biological response to temperature-mediated cancer therapies. Preliminary research has been conducted to identify and analyze the trends in temperature measurements from FBG's placed within phantoms that mimic the optical characteristics of human tissue. Shifts of the Bragg wavelength at selected temperature intervals depict the temperature of the phantom relative to room temperature. The scattering properties of tissue were achieved in the phantom by using 0.665 g of titanium dioxide (TiO2 - Titanium (IV) oxide, anatase) nanopowder, with a particle size smaller than 25 nm, which was mixed into 475 mL of Penecro’s Versagel (hydrocarbon material). This mixture imitates the tissue’s index of refraction of ~1.4. Shifts in the Bragg wavelength were measured using a spectrum analyzer at temperature intervals at approximately 25°C, 30°C, 35°C, 40°C, 45°C, 50°C, 55°C and 60°C. The results show that the relative Bragg wavelength is directly proportional to any increase or decrease of temperature in the phantom. In the case of these experiments, it was observed that the change in the bragg wavelength shift increased the phantom’s temperature was also increased with respect to the temperature set by the hot plate. The FBG regions that monitored temperature variations within the tissue-mimicking phantoms were also imaged, via OCT, to investigate temperature induced changes in the OCT images including investigation of changes in the OCT envelope statistics. This data may provide the base line to detect changes in the biological response to temperature variations, based solely on OCT images, and ultimately provide suitable imaging metric(s) to predict therapeutic outcome.
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Subaagari Seevaratnam, Mashal Farid, Golnaz Farhat, and Beau A. Standish "Analyzing effects of temperature on tissue equivalent phantoms using fiber Bragg gratings and optical coherence tomography", Proc. SPIE 8915, Photonics North 2013, 891504 (11 October 2013);

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