An improved polarization-sensitive optical coherence tomography (OCT) system is developed and used to measure birefringence in porcine myocardium tissue and produce two-dimensional birefringence mapping of the tissue. Signal-to-noise issues that cause systematic measurement errors are analyzed to determine the regime in which such measurements are accurate. The advantage of polarization-sensitive OCT systems over standard OCT systems in avoiding image artifacts caused by birefringence is also demonstrated.
We demonstrate cross-sectional birefringence- and polarization-independent backscatter imaging of laser-induced thermal damage in porcine myocardium in vitro, using a polarization-sensitive optical coherence tomography system. We compare the generated images with histological sections of the tissue and demonstrate that birefringence is a more sensitive indicator of thermal damage than is backscattered light. Loss of birefringence in thermally damaged regions is quantified and shown to have significant contrast with undamaged sections of the tissue. A detailed theoretical analysis of the birefringence measurements is provided, including a calculation of the systematic errors associated with background noise, system imperfections, and tissue dichroism.
End-to-end carotid artery anastomoses and aorta arteriotomy closure in rats have been performed using a diffraction limited semiconductor MOPA laser, coupled to an operating microscope and emitting a 1 watt continuous power output at a wavelength of 985 nm. Laser aiming was performed using an eyeguided laser targeting prototype, which allows to direct the laser with a beam steering unit controlled by the surgeon's eye movements. Preliminary results show that efficient welds can be obtained with the MOPA laser with irradiances of 670 and 1 195 W/cm2. The ease and efficiency of the eye-guided procedures enabled to close up to 5 mm long arteriotomies in the rat aorta and to accurately perform laser assisted microvascular anastomoses of rat carotid arteries. These laser welding procedures demonstrate the feasibility of eyeguided laser targeting in laser microsurgery.
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