Deep reflection-mode photoacoustic imaging of internal organs

A deep reflection-mode photoacoustic imaging system was developed and demonstrated to possess a maximum imaging depth up to 38 mm in chicken breast tissue. Using this system, structures in the thoracic cavity and vasculature in cervical area of rats were clearly imaged. Particularly, part of the heart was imaged. In the thoracic cavity, the right atrium imaged, which is one of deepest, was situated ~7 mm deep. In the cervical area, common carotid artery and jugular vein were imaged, which are appropriate for the study of oxygenation between artery and vein. In the abdominal cavity, the embedded structures of a kidney, spinal cord, and vena cava inferior were also clearly imaged in situ and in vivo. The depth of the vena cava inferior was as deep as ~15 mm in vivo. This study shows the depth capability of the system in animals. This imaging modality can be a useful tool to diagnose the disease of organs by assessing the morphological and functional changes in the blood vessels and the organs

Deep reflection-mode photoacoustic imaging of biological tissue

A reflection-mode photoacoustic (PA) imaging system was designed and built to image deep structures in biological tissues. We chose near-infrared laser pulses of 804-nm wavelength for PA excitation to achieve deep penetration. To minimize unwanted surface signals, we adopted dark-field ring-shaped illumination. This imaging system employing a 5-MHz spherically focused ultrasonic transducer provides penetration up to 38mm in chicken breast tissue. At the 19-mm depth, the axial resolution is 144μm and the transverse resolution is 560μm. Internal organs of small animals were imaged clearly

Synergistic effect of a defect-free graphene nanostructure as an anode material for lithium ion batteries

© 2019 by the authors. Licensee MDPI, Basel, Switzerland.Graphene nanosheets have been among the most promising candidates for a highperformance anode material to replace graphite in lithium ion batteries (LIBs). Studies in this area have mainly focused on nanostructured electrodes synthesized by graphene oxide (GO) or reduced graphene oxide (rGO) and surface modifications by a chemical treatment. Herein, we propose a cost-effective and reliable route for generating a defect-free, nanoporous graphene nanostructure (df-GNS) through the sequential insertion of pyridine into a potassium graphite intercalation compound (K-GIC). The as-prepared df-GNS preserves the intrinsic property of graphene without any crystal damage, leading to micro-/nano-porosity (microporosity: ~10–50 µm, nanoporosity: ~2– 20 nm) with a significantly large specific surface area. The electrochemical performance of the dfGNS as an anode electrode was assessed and showed a notably enhanced capacity, rate capability, and cycle stability, without fading in capacity or decaying. This is because of the optimal porosity, with perfect preservation of the graphene crystal, allowing faster ion access and a high amount of electron pathways onto the electrode. Therefore, our work will be very helpful for the development of anode and cathode electrodes with higher energy and power performance requirement

Three-dimensional in vivo near-infrared photoacoustic tomography of whole small animal head

A three-dimensional in vivo near-infrared photoacoustic tomography imaging system was newly designed and built to visualize the structure of a whole small animal head. For high sensitivity, a single flat 2.25MHz low frequency transducer, whose active element size is 6mm, was employed. To increase the penetration depth of light, a wavelength of 804nm in the NIR range, which matches the oxy- and deoxy-hemoglobin isosbestic point, was chosen. To avoid strong photoacoustic signal generation from the skin surface, we applied dark field illumination. To illuminate efficiently, we split the laser light into two beams, which were delivered to an animal by two mirrors and were finally homogenized by two ground glasses. To complete the dark field illumination, the transducer was located in the middle of two light sources. Two key devices for the in vivo imaging were rotating devices and animal holders. The rotating devices were composed of two parts, located at the top and bottom, which rotated at the same angular speed. The holders were composed of a head holder and a body holder. Both holders fixed the animal firmly to reduce motion artifacts. This system achieved radial resolution of up to 260μm. We accomplished successful in vivo imaging of arterial and venous vessels deeply, as well as superficially, with the animal head of up to 1.7cm diameter. The technique forms a basis for functional imaging, such as measurement of the oxygen consumption ratio in the brain, which is a vital parameter in a brain disease research

In vivo dual-modality imaging of lymphatic systems using indocyanine green in rats: three-dimensional photoacoustic imaging and planar fluorescence imaging

The purpose of this study is to map non-invasively sentinel lymph nodes (SLNs) and lymphatic vessels of rats in vivo using FDA-approved indocyanine green (ICG) and two non-ionizing imaging modalities: volumetric spectroscopic photoacoustic (PA) imaging, which measures optical absorption, and planar fluorescence imaging, which measures fluorescent emission. SLNs and lymphatic vessels were clearly visible after a 0.2 ml-intradermal-injection of 1 mM ICG in both imaging systems. We also imaged deeply positioned lymph nodes in vivo by layering biological tissues on top of rats. These two modalities, when used together with ICG, have the potential to map SLNs in axillary staging and to study tumor metastasis in breast cancer patients

Sentinel lymph node detection ex vivo using ultrasound-modulated optical tomography

We apply ultrasound-modulated optical tomography (UOT) to image ex-vivo methylene-blue-dyed sentinel lymph nodes embedded in 3.2-cm-thick chicken breast tissues. The UOT system is implemented for the first time using ring-shaped light illumination, intense acoustic bursts, and charge-coupled device (CCD) camera-based speckle contrast detection. Since the system is noninvasive, nonionizing, portable, relatively cost effective, and easy to combine with photoacoustic imaging and single element ultrasonic pulse-echo imaging, UOT can potentially be a good imaging modality for the detection of sentinel lymph nodes in breast cancer staging in vivo

In vivo three-dimensional photoacoustic tomography of a whole mouse head

An in vivo photoacoustic imaging system was designed and implemented to image the entire small animal head. A special scanning gantry was designed to enable in vivo imaging in coronal cross sections with high contrast and good spatial resolution for the first time to our knowledge. By use of a 2.25 MHz ultrasonic transducer with a 6 mm diameter active element, an in-plane radial resolution of ∼312  µm was achieved. Deeply seated arterial and venous vessels in the head measuring up to 1.7 cm in diameter were simultaneously imaged in vivo with 804 nm wavelength laser excitation of photoacoustic waves

Vision-based Crack Identification on the Concrete Slab Surface using Fuzzy Reasoning Rules and Self-Organizing

Identifying cracks on the surface of concrete slab structure is important for structure stability maintenance. In order to avoid subjective visual inspection, it is necessary to develop an automated identification and measuring system by vision based method. Although there have been some intelligent computerized inspection methods, they are sensitive to noise due to the brightness contrast and objects such as forms and joints of certain size often falsely classified as cracks. In this paper, we propose a new fuzzy logic based image processing method that extracts cracks from concrete slab structure including small cracks that were often neglected as noise. We extract candidate crack areas by applying fuzzy method with three color channel values of concrete slab structure. Then further refinement processes are performed with Self Organizing Map algorithm and density based noise removal process to obtain basic crack characteristic attributes for further analysis. Experimental result verifies that the proposed method is sufficiently identified cracks with various sizes with high accuracy (97.3%) among 1319 ground truth cracks from 30 images

DETERMINATION OF LINEAR AND NONLINEAR ROLL DAMPING COEFFICIENTS OF A SHIP SECTION USING CFD

The most prevalently used method to obtain the nonlinear roll damping coefficient is the free roll decay test. However, this method can only be conducted at the resonance frequency and thus cannot consider the effect of the frequency. This is a certain limitation as the resonance frequency can be changed at any time by the ship’s loading conditions. Therefore, it is worth investigating the frequency dependency of the nonlinear roll damping coefficients. In this study, a numerical method was proposed to derive the linear and nonlinear roll damping coefficients of ships at different frequencies. Fully nonlinear CFD simulations of forced harmonic roll motion were conducted and the roll damping coefficients were calculated. Then, the damping coefficients were decomposed into the linear and nonlinear components using the linear regression analysis. The linear roll damping coefficients were compared with potential coefficients and showed a good agreement, while the nonlinear roll damping coefficients were compared with the coefficients calculated using a semi-empirical method. The nonlinear roll damping coefficients calculated from the proposed method showed a strong frequency dependency. Finally, possible rationales for the frequency dependence of the nonlinear roll damping coefficient were investigated