Birefringence Measurement of Rapid Structural Changes during Collagen Denatu ration

Abstract— Linear birefringence, an optical property that results from a material's structure and composition, can be used to study dynamic changes in tissue structure. Single, 200 μs‐long pulses from a Ho:YAG laser emitting 2.1 μm radiation were used to induce changes in the linear birefringence of rat tail tendon. Such changes were measured on a millisecond timescale. The measured rate coefficients describing the denaturation are not predicted by previous studies of collagen denaturation induced by slower, lower‐temperature heating. Two types of laser‐induced collagen denaturation can be differentiated: thermal denaturation, which appears rate‐limited, and thermomechanical denaturation, which is observed at higher laser radiant exposures. Neither process is described by standard Arrhenius‐type kinetic models.

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