Special Section Guest Editorial - Tissue Polarimetry

Tissue polarimetry is an emerging area of technology development in tissue optics that is expected to lead to important research applications in biology and medicine. Traditional polarimetry is a mature field, but its application to thick tissues has been hindered by technical hurdles associated with multiple light scattering. However, light is intrinsically polarized; and many biological tissue components or molecules—such as collagen, muscle fibers, keratin, retina, and glucose—possess polarization properties. Further, biological scatterers—such as cell nuclei and mitochondria—alter light polarization upon each scattering event according to the geometric and optical parameters of the scatterers. Since incident polarized light is rapidly depolarized by scattering, polarization-sensitive detection of reflected or transmitted light selects only the early escaping photons and rejects multiply scattered light. Hence, polarized light offers a means of gating: reflected polarized photons interrogate superficial tissue layers, whereas transmitted polarized photons image the ballistic or quasi-ballistic region. Polarization can therefore provide novel contrast mechanisms for imaging, diagnosis, and sensing

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Two women struggle to sustain a sense of private identity in a boarding house for elderly ladies. They live within imposed roles that deny all recognition of their individuality

Light backscattering polarization patterns from turbid media: theory and experiment

We present both experimental measurements and Monte-Carlo-based simulations of the diffusely backscattered intensity patterns that arise from illuminating a turbid medium with a polarized laser beam. It is rigorously shown that, because of axial symmetry of the system, only seven elements of the effective backscattering Mueller matrix are independent. A new numerical method that allows simultaneous calculation of all 16 elements of the two-dimensional Mueller matrix is used. To validate our method we compared calculations to measurements from a turbid medium that consisted of polystyrene spheres of different sizes and concentrations in deionized water. The experimental and numerical results are in excellent agreement

Training agricultural scientists at the International Center for the Improvement of Maize and Wheat

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Bibliography: leaves 155-163.Not availabl

Real-time, closed-loop dual-wavelength optical polarimetry for glucose monitoring

The development of a real-time, dual-wavelength optical polarimetric system to ultimately probe the aqueous humor glucose concentrations as a means of noninvasive diabetic glucose monitoring is the long-term goal of this research. The key impact of the work is the development of an approach for the reduction of the time-variant corneal birefringence due to motion artifact, which is still a limiting factor preventing the realization of such a device. Our dual-wavelength approach utilizes real-time, closed-loop feedback that employs a classical three-term feedback controller and efficiently reduces the effect of motion artifact that appears as a common noise source for both wavelengths. In vitro results are shown for the open-loop system, and although the dual-wavelength system helps to reduce the noise, it is shown that closed-loop control is necessary to bring the noise down to a sufficient level for physiological monitoring. Specifically, in vitro measurement results with the closed-loop dual-wavelength approach demonstrate a sensitivity of 12.8 mg∕dl across the physiologic glucose range in the presence of time-variant test cell birefringence. Overall, it is shown that this polarimetric system has the potential to be used as a noninvasive measure of glucose for diabetes

Diffuse reflectance polarization images of turbid media affected by glucose

Diffuse reflectance polarimetry has been used to obtain images from tissue-simulating turbid media with different glucose concentrations to investigate the changes in the polarization patterns induced by glucose. The optical properties change as the concentration of glucose is varied in the medium. The polarization patterns are affected by the overall optical properties of the turbid medium under study. This approach has potential applications in actual biological tissues for rapidly determining glucose levels non-invasively