Investigating laser-induced fluorescence of metabolic changes in Guinea pig livers during Nd:YAG laser irradiation

Recently, dosimetry of thermal influences on biological tissue has been attracting more and more interest among scientists. For temperatures exceeding 56 °C, the irreversible tissue coagulation can be approximately described by the Arrhenius theory, which was established in chemical kinetics. Investigations in the temperature range between 43 °C and 55 °C are rare and are, therefore, not available in a systematic form. A Nd:YAG laser (1060 nm) was used, to heat up liver tissue of guinea pigs in this temperature range periodically at intervals of ca. 3 minutes. A second laser (N2, 337 nm) was used to simultaneously excite the autofluorescence of NADH as coenzyme of the cell respiration. The results of the measurement series show strong inter‐individual variations of the metabolic decay time. The Arrhenius theory fails to provide a description in this temperature range thus opening up new modeling possibilities. (© 2005 by ASTRO, Ltd. Published exclusively by WILEY‐VCH Verlag GmbH & Co. KGaA)