RESUMEN
Light propagation wavefront and photon composition variations occur when the beam encounters acoustic waves, bringing mechanical and chemical inhomogeneity-induced light-intensity modulation, while phase variations, which carry more information about the acoustic-optical coupling in the medium, are often overlooked. This paper investigates the coupling of the light beam with the propagating ultrasound and the polarization aberration of the optical wave induced by the ultrasound. A model was developed to express the variation of the ultrasound-induced polarization aberration (UIPA). The ultrasound-induced refractive index variation of the sample was observed in both the simulation and experiments. The phase differences in various ultrasound states (valley dominant state, peak dominant state) are characterized in detail. The UIPA expressed in the phase space provides a way to quantify multidimensional polarization information of the ultrasound-tagged optical waves and allows refraction-sensitive polarization parametric imaging, which may be exploited for directional high-contrast photoacoustic imaging with ultrasound tagging.
RESUMEN
Most photoacoustic computed tomography (PACT) systems usually ignore the anisotropy of the tissue absorption coefficient, which will lead to the lack of information in reconstructed images. In this work, the effect is addressed of the possible optical absorption anisotropy of tissue on PACT images. The functional relationship is derived between the photoacoustic response and the polarization angle of the excitation light. An adaptive polarized light photoacoustic imaging (AP-PACT) approach is proposed and shown to make up for the lack of imaging information and achieve optimal image contrast when imaging samples with anisotropic optical absorption, by utilizing the standard deviation of photoacoustic response as the feedback signal in an adaptive data acquisition process. The method is implemented both on phantom and in vitro experiments, which show that AP-PACT can recover anisotropic absorption-related information from reconstructed images and thus significantly improve their quality.
RESUMEN
In biomedical imaging, photoacoustic computed tomography (PACT) has recently gained increased interest as this imaging technique has good optical contrast and depth of acoustic penetration. However, a spinning blur will be introduced during the image reconstruction process due to the limited size of the ultrasonic transducers (UT) and a discontinuous measurement process. In this study, a damping UT and adaptive back-projection co-optimization (CODA) method is developed to improve the lateral spatial resolution of PACT. In our PACT system, a damping aperture UT controls the size of the receiving area, which suppresses image blur at the signal acquisition stage. Then, an innovative adaptive back-projection algorithm is developed, which corrects the undesirable artifacts. The proposed method was evaluated using agar phantom and ex-vivo experiments. The results show that the CODA method can effectively compensate for the spinning blur and eliminate unwanted artifacts in PACT. The proposed method can significantly improve the lateral spatial resolution and image quality of reconstructed images, making it more appealing for wider clinical applications of PACT as a novel, cost-effective modality.
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A stroboscopic method based on polarization selective imaging is proposed for dynamic visualization of ultrasonic waves propagating in a transparent medium. Multiple independent polarization parametric images were obtained, which enabled quantitative evaluation of the distribution of the ultrasonic pressure in quartz. In addition to the detection of optical phase differences δ in conventional photo-elastic techniques, the azimuthal angle φ and the Stokes parameter S2 of the polarized light are found to be highly sensitive to the wave-induced refraction index distribution, opening a new window on ultrasonic field visualization.
RESUMEN
Objective@#To investigate current status and associated factors of preschool children’s physical fitness, in order to provide scientific basis for improving preschool children’s physical fitness.@*Methods@#A total of 3 240 preschool children aged 3-6 years old in Kunshan city were selected through cluster sampling method. They were surveyed about physical fitness and influencing factors.@*Results@#The number of excellence of preschool children’s physical fitness was 269, and the rate was 8.30 percent. The excellence rates of preschool children’s physical fitness in girls, high grade, non-residency in Jiangsu Province were higher(10.87%, 10.96%, 14.88%), and the excellence rate of preschool children’s physical fitness in premature group was lower(4.31%)(P<0.05). Further unconditioned logistic regression analysis found that girls, middle and high grade and non-residency in Jiangsu Province were the protective factors for the excellence of preschool children’s physical fitness, OR values were 1.96, 1.94, 2.45 and 1.87, respectively; premature was a risk factor for the excellence of preschool children’s physical fitness, OR value was 0.47.@*Conclusion@#Preschool children in Kunshan have poor physical fitness, especially in boys, low grade and premature groups. Education department and health department should work together to improve the preschool children’s physical fitness.
