KEYWORDS: Optical coherence tomography, Fiber optics, Polarization, Phase modulation, Calibration, Mirrors, In vivo imaging, Birefringence, Signal to noise ratio, Interferometers
A swept source (SS)-based circular-state (CS) polarization-sensitive optical coherence tomography (PS-OCT) constructed entirely with polarization-maintaining fiber optics components is proposed with the experimental verification. By means of the proposed calibration scheme, bulk quarter-wave plates can be replaced by fiber optics polarization controllers to, therefore, realize an all-fiber optics CS SSPS-OCT. We also present a numerical dispersion compensation method, which can not only enhance the axial resolution, but also improve the signal-to-noise ratio of the images. We demonstrate that this compact and portable CS SSPS-OCT system with an accuracy comparable to bulk optics systems requires less stringent lens alignment and can possibly serve as a technology to realize PS-OCT instrument for clinical applications (e.g., endoscopy). The largest deviations in the phase retardation (PR) and fast-axis (FA) angle due to sample probe in the linear scanning and a rotation angle smaller than 65 deg were of the same order as those in stationary probe setups. The influence of fiber bending on the measured PR and FA is also investigated. The largest deviations of the PR were 3.5 deg and the measured FA change by ∼12 to 21 deg. Finally, in vivo imaging of the human fingertip and nail was successfully demonstrated with a linear scanning probe.
Prior studies have established the necessity of an angiotensin-converting enzyme-related (ACER) gene for heart morphogenesis of Drosophila. Nevertheless, the physiology of ACER has yet to be comprehensively understood. Herein, we employed RNA interference to down-regulate the expression of ACER in Drosophila’s heart and swept source optical coherence tomography to assess whether ACER is required for cardiac functions in living adult flies. Several contractile parameters of Drosophila heart, including the heart rate (HR), end-diastolic diameter (EDD), end-systolic diameter (ESD), percent fractional shortening (%FS), and stress-induced cardiac performance, are shown, which are age dependent. These age-dependent cardiac functions declined significantly when ACER was down-regulated. Moreover, the lifespans of ACER knock-down flies were significantly shorter than those of wild-type control flies. Thus, we posit that ACER, the Drosophila ortholog of mammalian angiotensin-converting enzyme 2 (ACE2), is essential for both heart physiology and longevity of animals. Since mammalian ACE2 controls many cardiovascular physiological features and is implicated in cardiomyopathies, our findings that ACER plays conserved roles in genetically tractable animals will pave the way for uncovering the genetic pathway that controls the renin-angiotensin system.
We report a semiautomatic algorithm that is specialized for rapid analysis of beat-to-beat contraction-relaxation parameters of the heart in Drosophila. The presented algorithm adapts the general graph theoretical image segmentation algorithm and a histogram-based thresholding algorithm, which can measure many cardiac parameters, including heart rate, heart period, diastolic and systolic intervals, and end-diastolic and end-systolic areas. Additionally, dynamic cardiac functions, such as arrhythmia index and percent fractional shortening, can be automatically calculated for all the recorded heartbeats over significant periods of time.
Ionizing radiation is a standard treatment for various human solid tumors. However, several clinical studies showed that
a significant proportion of patients undergoing radiotherapy for hepatocellular carcinoma (HCC) develop intrahepatic
and extrahepatic metastasis. Understanding of radiation-induced cancer cell invasiveness and behavior is essential and of
great important for developing suitable treatment strategies to contain cancer spread. Therefore, in this study we
evaluated the effectiveness of using swept source optical coherence tomography (SS-OCT) to monitor the enhancement
of HCC cell invasiveness by radiation. SS-OCT images were acquired and recorded to obtain three-dimensional data sets
per four hours in 48 hours after irradiating HepG2 cells with 7.5 Gy. The cell migration behavior in three-dimensional
tissue models was quantified from images of radiation-induced and sham-irradiated cells.
In this research, we have used an algorithm to extract four different optical parameters, including the scattering coefficient (μs), effective anisotropy factor (goff), birefringence coefficient (Δn), and fast-axis angle (β) from polarization-sensitive optical coherence tomography (PS-OCT) images. The proposed method was evaluated from a set of phantoms and it yielded valid results. We demonstrate that the optical characteristic of normal and different kinds of atherosclerotic lesions in human vessel can be quantitatively described. Whether change in these quantified optical properties could be used to discriminate between different types of human atherosclerotic plaques was examined.
Refractive-index mismatch in conventional confocal microscopy produces severe degradation on axial resolution of
sectioning image because the spherical aberration is generated in specimen. In this study, we propose a polarized
photon-pairs confocal laser scanning microscope (PCLSM) in which a two-frequency linear polarized photon-pairs
(LPPPs) laser beam is produced. The common-path propagation of LPPPs integrated with optical heterodyne technique
not only can reduce the spherical aberration but also decreases scattering effect in specimen at same time. Therefore, the
better axial and lateral resolutions of the sectioning image are produced simultaneously. In the experiment, a verification
and comparison between PCLSM and conventional confocal laser scanning microscope (CLSM) on the ability of
cancellation of spherical aberration induced by cover glass are demonstrated experimentally. Finally, the ability of
PCLSM which can decrease the spherical aberration based on the common-path propagation of LPPPs associated with
polarization gating, spatial coherence gating and spatial filtering gating is discussed.
We developed a novel differential-phase optical coherence reflectometer (DP-OCR) by using a low-coherence light
source and integrated with differential phase detection technique on surface profile measurement. In this setup, 2Å on
detection of axial displacement was demonstrated. Thus, a localized surface profile was measured precisely by
scanning an optical grating surface in this measurement. Moreover, the requirement on equal amplitude of the reference
and signal beams of this novel reflectometer is discussed.
Atherosclerosis is unquestionably the leading cause of morbidity and mortality in developed countries. In the mean time, the worldwide importance of acute vascular syndromes is increasing. Because collagen fiber is a critical component of atherosclerotic lesions; it constitutes up to 60% of the total atherosclerotic plaque protein. The uncontrolled collagen accumulation leads to arterial stenosis, whereas excessive collagen breakdown weakens plaques thereby making them prone to rupture finally. Thus, in this study, we present the first application, to our knowledge, of using polarization-sensitive optical coherence tomography (PS-OCT) in human atherosclerosis. We demonstrate this technique for imaging of intensity, birefringence, and fast-axis orientation simultaneously in atherosclerotic plaques. This in vitro study suggests that the birefringence change in plaque is due to the prominent deposition of collagen according to the correlation of PS-OCT images with histological counterpart. Moreover, we can acquire quantitative criteria based on the change of polarization of incident beam to estimate whether the collagen synthesized is "too much" or "not enough". Thus by combining of high resolution intensity imaging and birefringence detection makes PS-OCT could be a potentially powerful tool for early assessment of atherosclerosis appearance and the prediction of plaque rupture in clinic.
A novel optical heterodyne surface plasmon resonance (SPR) biosensor using Zeeman laser is proposed. There are two surface plasma waves (SPWs) being excited by two correlated P polarized waves in an SPR device of Kretschmann configuration. The two reflected P waves are optically heterodyned so that the amplitude of the heterodyned signal is proportional to the multiplication of two attenuated reflected P waves. The detection sensitivity and the dynamical range based on this amplitude sensitive method are enhanced. In the experiment, the kinetics between mouse IgG and anti-mouse IgG is obtained according to the sensograms of different concentrations of anti-mouse IgG. The detection sensitivity corresponding to 0.2 nM is achieved. In addition, a concentration of 5 ng/ml of protein G interacting with mouse IgG is measured successfully.
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