A single miniature endoscope capable of concurrently probing multiple contrast mechanisms of tissue in high resolution is highly attractive, as it makes it possible for providing complementary, more complete tissue information on internal organs hard to access. Here we describe such a miniature endoscope only 1 mm in diameter that integrates photoacoustic imaging (PAI), optical coherence tomography (OCT), and ultrasound (US). The integration of PAI/OCT/US allows for high-resolution imaging of three tissue contrasts including optical absorption (PAI), optical scattering (OCT), and acoustic properties (US). We demonstrate the capabilities of this trimodal endoscope using mouse ear, human hand, and human arteries with atherosclerotic plaques. This 1-mm-diameter trimodal endoscope has the potential to be used for imaging of internal organs such as arteries, GI tracts, esophagus, and prostate in both humans and animals.

Prenatal ethanol exposure (PEE) can lead to structural and functional abnormalities in fetal brain. Although neural developmental deficits due to PEE have been recognized, the immediate effects of PEE on fetal brain vasculature and hemodynamics remain poorly understood. One of the major obstacles that preclude the rapid advancement of studies on fetal vascular dynamics is the limitation of the imaging techniques. Thus, a technique for noninvasive in-vivo imaging of fetal vasculature and hemodynamics is desirable. In this study, we explored the dynamic changes of the vessel dimeter, density and oxygen saturation in fetal brain after acute maternal ethanol exposure in the second-trimester equivalent murine model using a real-time photoacoustic tomography system we developed for imaging embryo of small animals. The results indicate a significant decrease in fetal brain vessel diameter, perfusion and oxygen saturation. This work demonstrated that PAT can provide highresolution noninvasive imaging ability to monitor fetal vascular dynamics. K E Y W O R D Sacute prenatal ethanol exposure, fetal alcohol spectrum disorder, fetal brain vasculature, hemodynamics, real-time photoacoustic tomography

Finite element method (FEM)-based time-domain quantitative photoacoustic tomography (TD-qPAT) is a powerful approach, as it provides highly accurate quantitative imaging capability by recovering absolute tissue absorption coefficients for functional imaging. However, this approach is extremely computationally demanding, and requires days for the reconstruction of one set of images, making it impractical to be used in clinical applications, where a large amount of data needs to be processed in a limited time scale. To address this challenge, here we present a graphic processing unit (GPU)-based parallelization method to accelerate the image reconstruction using FEM-based TD-qPAT. In addition, to further optimize FEM-based TD-qPAT reconstruction, an adaptive meshing technique, along with mesh density optimization, is adopted. Phantom experimental data are used in our study to evaluate the GPU-based TD-qPAT algorithm, as well as the adaptive meshing technique. The results show that our new approach can considerably reduce the computation time by at least 136-fold over the current central processing unit (CPU)-based algorithm. The quality of image reconstruction is also improved significantly when adaptive meshing and mesh density optimization are applied.

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A novel intensity-modulated directional torsion sensor based on a helical taper is proposed and experimentally demonstrated. The tapers are fabricated in standard single-mode fiber by electric-arc discharge, and by rotating one side fiber simultaneously. Experimental results show that the intensity of transmission peak changes inversely when the helical taper is twisted in clockwise and counterclockwise, respectively. The maximum torsion sensitivity can reach -0.484 dB/(rad/m) in the twist rate ranges from -10.67 rad/m to 0 rad/m. Additionally, this torsion sensor is almost insensitive to temperature, which solves the problem of torsion-temperature cross sensitivity greatly. The novel torsion sensor provides a promising candidate for the applications that require accurate rotation, such as civil engineering, the automotive industry, and security monitoring of buildings.