Dynamic measurement of laser-induced changes in rat tail tendon birefringence

Summary form only given. The authors report the birefringent response of rat tail tendon (RTT) to rapid heating by 200-/spl mu/s-long, 2.1-/spl mu/m Ho:YAG laser pulses. The results indicate that dynamic measurement of linear birefringence can be used as an optical feedback parameter to control laser tissue heating. Tendon samples were extracted from the tails of one-month old, Sprague Dawley rats. The tendon fibers were rinsed, stored in saline, arid used within 48 hrs post mortum. Single, 150-/spl mu/m-diameter fibers were mounted between quartz flats in 10 /spl mu/l of saline. A 100-/spl mu/m-thick gasket was used to fix the pathlength of light through the RTT. The sample was placed between crossed polarizers and illuminated with a probe beam from a 5-mW HeNe laser. The signal transmitted through the crossed polarizers was attributed solely to the tendon birefringence. A Ho:YAG laser beam served as the heat source. The authors´ preliminary data are consistent with the premise that linear birefringence can be used to detect small changes in tissue structure sensitively. They further suggest that because the change in birefringence occurs on a millisecond timescale, birefringence could be used to study the rapid kinetics of tissue structure changes during laser heating.