Myocardial infarction (MI), a cause of significant morbidity and mortality, is typically followed by microstructural alterations where the necrotic myocardium is steadily replaced with a collagen scar. Engineered remodeling of the fibrotic scar via stem cell regeneration has been shown to improve/restore the myocardium function after MI. Nevertheless, the heterogeneous nature of the scar patch may impair the myocardial electrical integrity, leading to the formation of arrhythmogenesis. Radiofrequency ablation (RFA) offers an effective treatment for focal arrhythmias where local heating generated via electric current at specific spots in the myocardium ablate the arrhythmogenic foci. Characterization of these myocardial pathologies (i.e., infarcted, stem cell regenerated, and RFA-ablated myocardial tissues) is of potential clinical importance. Optical polarimetry, the use of light to map and characterize the polarization signatures of a sample, has emerged as a powerful imaging tool for structural characterization of myocardial tissues, exploiting the underlying highly fibrous tissue nature. This study aims to review the recent progress in optical polarimetry pertaining to the characterization of myocardial pathologies while describing the underlying biological rationales that give rise to the optical imaging contrast in various pathologies of the myocardium. Future possibilities of and challenges to optical polarimetry in cardiac imaging clinics are also discussed.

https://www.spiedigitallibrary.org/journals/journal-of-biomedical-optics/volume-22/issue-10/100901/Review-of-the-emerging-role-of-optical-polarimetry-in-characterization/10.1117/1.JBO.22.10.100901.pdf

Review of the Emerging Role of Optical Polarimetry in Characterization of Pathological Myocardium

An image capture device includes an electro-optics arrangement having an arrangement of polarizers, polarization sensitive optical elements, and polarization modulating elements. First and second polarization sensitive optical elements are provided having an edge displaced relative to a plane normal to an optical axis of the electro-optics arrangement. A control system coupled to the electro-optics arrangement controls the application of voltages to the polarization modulating elements to control the polarization rotation of the light input to the polarization sensitive optical elements, such that the optical path length of the polarization sensitive optical elements is changed to provide for capture of the object images at each of the different focal planes. The first and second polarization sensitive optical elements generate lateral image shifts between respective object images captured at the different focal planes responsive to the polarization rotation of the light input thereto.

Apparatus and method for image super-resolution using integral shifting optics

The invention relates to a double refraction realtime measuring device and method. The device is characterized by comprising an alignment light source, a circular polarizer, a spectroscope, a first Wollaston prism, a second Wollaston prism, a first double quadrant detector, a second double quadrant detector and a signal processing unit. According to the device and the method, double refraction of a sample can be measured in real time, and the measurement result is not affected by light-intensity variation.

Double refraction realtime measuring device and method

Real-time measurement of retardation and fast axis azimuth of wave plates is proposed. The light emitted from the laser passes through a circular polarizer and the sample successively. Then the beam is diffracted to three sub-beams by a grating. One sub-beam passes through a standard quarter-wave plate and then is split and analyzed by a Wollaston prism. The other two sub-beams are all directly split and analyzed by Wollaston prisms. Six intensities are simultaneously detected to calculate the retardation and the fast axis azimuth. Experiments show that for the quarter-wave plate the average and standard deviation of the retardation are 89.78° and 0.14°, respectively, and the maximum deviation of the fast axis azimuth is 0.6°; for the eighth-wave plate, the average and standard deviation of the retardation are 45.15° and 0.15°, respectively, and the maximum deviation of the fast axis azimuth is 0.53.

Real-time measurement of retardation and fast axis azimuth for wave plates

An alternative method is proposed for simultaneously measuring the phase retardation and fast axis angle of a wave plate by utilizing a radially polarized symmetric light beam. A horizontal polarized laser is passed through a spatial filter, a zero-order vortex half-wave retarder, for measuring the light beam. An analyzer and a charge-coupled device are used for the measurement. The charge-coupled device captures two intensity variation patterns before and after a wave plate to be tested is rotated by 45° in any initial fast axis angle direction. Through analysis of the intensity values, the phase retardation and fast axis angle of the wave plate to be tested can be accurately determined using mean calculation. To validate the proposed method, half-wave and quarter-wave plates were measured experimentally. The measurement errors of phase retardation and fast axis angle were approximately 0.087° and 0.094°, respectively.

Alternative method for measuring the phase retardation and fast axis of a wave plate

Simultaneous measurement of small birefringence magnitude and direction in real time

The invention relates to a linear birefringence measuring device and a measuring method thereof. The linear birefringence measuring device comprises a collimating light source with light intensity modulation, a circular polarizer, a Wollaston prism, a dual-quadrant detector and a signal processing unit, wherein the position relation of elements is as follows: the circular polarizer, the Wollaston prism and the dual-quadrant detector are sequentially arranged along the forward direction of a light beam output from the collimating light source with light intensity modulation, the output end of the dual-quadrant detector is connected with the input end of the signal processing unit, and a spigot of a linear birefringence sample to be measured is arranged between the circular polarizer and the Wollaston prism. The linear birefringence measuring device has simple structure and convenience for measurement and operation; in the invention, the phase retardation and the fast axis azimuth angle of the linear birefringence sample can be simultaneously measured, and a measuring result is not influenced by the light intensity variation of the collimating light source.

Linear birefringence measuring device and measuring method thereof

Simultaneous measurement of the birefringence magnitude and direction using Wollaston prism is presented. The
sinusoidally modulated laser beam passes through a circular polarizer, the birefringence sample and is split by a
Wollaston prism. The measuring beam is then detected by a bi-cell detector and two alternating current signals are
detected. Then the Wollaston prism is rotated by 45°, and another two alternating current signals are obtained. By
processing the four signals, the birefringence magnitude and direction is resolved simultaneously. In experiments, a
wedge waveplate was laterally moved and measured at different birefringence magnitude. The measured birefringence
magnitude linearly increased as the wedge waveplate was laterally moved. The maximum standard deviation of the
birefringence magnitude and direction is 0.11° and 0.05°The usefulness of this method is verified.

Beishi Chen

Papers

Simultaneous measurement of small birefringence magnitude and direction in real time

Linear birefringence measuring device and measuring method thereof

Simultaneous measurement of birefringence magnitude and direction using Wollaston prism