Optics express
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Technique of loss-of-resistance in epidural block is commonly used for epidural anesthesia in humans with approximately 90% successful rate. However, it may be one of the most difficult procedures to learn for anesthesia residents in hospital. ⋯ In an in-vivo study in piglets showed that the reflected lights from ES and its surrounding tissue ligamentum flavum (LF) are highly distinguishable. This indicates that this technique has potential to localize the ES on the spot without the help of additional guiding assistance.
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Remote measurements of the cardiac pulse can provide comfortable physiological assessment without electrodes. However, attempts so far are non-automated, susceptible to motion artifacts and typically expensive. In this paper, we introduce a new methodology that overcomes these problems. ⋯ Using Bland-Altman and correlation analysis, we compared the cardiac pulse rate extracted from videos recorded by a basic webcam to an FDA-approved finger blood volume pulse (BVP) sensor and achieved high accuracy and correlation even in the presence of movement artifacts. Furthermore, we applied this technique to perform heart rate measurements from three participants simultaneously. This is the first demonstration of a low-cost accurate video-based method for contact-free heart rate measurements that is automated, motion-tolerant and capable of performing concomitant measurements on more than one person at a time.
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"Diffuse correlation spectroscopy" (DCS) is a technology for non-invasive transcranial measurement of cerebral blood flow (CBF) that can be hybridized with "near-infrared spectroscopy" (NIRS). Taken together these methods hold potential for monitoring hemodynamics in stroke patients. ⋯ Moreover, the presence of an ipsilateral infarct was a significant effect for all parameters. Results are consistent with the notion of impaired CBF autoregulation in the infarcted hemisphere.
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A method to measure the size, orientation, and location of opaque micro-fibers using digital holography is presented. The method involves the recording of a digital hologram followed by reconstruction at different depths. ⋯ The performance of the proposed method is verified with a single fiber of known length and orientation. The potential of the method for measurement of fiber length is further demonstrated through its application to a suspension of fibers in a liquid medium.
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Optical traps use the forces exerted by structured beams of light to confine and manipulate microscopic objects in three dimensions. A popular implementation involves structuring the trap-forming beam with computer-generated holograms before focusing it into traps with a high-numerical-aperture optical train. Here, we present a fully vectorial theory for the forces and torques exerted by such systems.