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8 May 1997 Feasibility study of PDT light sources based on lasing action in strongly scattering media
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Lasing action in strongly scattering media containing a fluorescent dye and pumped by a pulsed high peak power laser can be used to produce light sources which may be suitable for surface or intracavity light delivery in photodynamic therapy, eliminating the need for a dye laser to obtain selectable treatment wavelengths. The present study focuses on evaluating the effects, in cylindrical fiber tip sources for interstitial light delivery, of fluorophore concentration and scattering particle density on lasing peak power, emission wavelength and maximum deliverable, clinically useful fluence-rate and radiant exposure. The sources tested are comprised of Rhodamine 640 perchloride incorporated into a TiO2 based scattering matrix in either ethylene glycol or methanol. The cylindrical fiber tips, 10 mm long and 2 mm in diameter, were pumped via a 320 micrometers diameter multimode optical fiber, achieving line narrowing to approximately 7 nm FWHM at approximately 617 nm, using pulse energies of 1.7 mJ, delivered in 10 nsec from a Q-switched, frequency doubled Nd:YAG laser. The results showed the dependence of the total gain length in the pump volume and reabsorption effects in the remaining volume of the fiber tip. Sources capable of delivering sufficient radiant exposure for clinical use were achieved. While these sources are promising, for clinical use of these fiber sources pump lasers delivering MW pulses at high repetition rates are required to achieve acceptable total irradiation times.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lothar D. Lilge, Gendi Pang, James Jonkman, and Brian C. Wilson "Feasibility study of PDT light sources based on lasing action in strongly scattering media", Proc. SPIE 2972, Optical Methods for Tumor Treatment and Detection: Mechanisms and Techniques in Photodynamic Therapy VI, (8 May 1997);

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