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The transparent [Li 0.04 (K 0.5 Na 0.5) 0.96 ]NbO 3 +0.5mol% Er 2 O 3 (KNNLN-Er) lead-free piezoelectric ceramics were prepared by stereolithography technique. The influence of different sintering holding time (4h∼8h) on the micromorphology, relative density, shrinkage, electric properties, and photoluminescence properties were systematically investigated. The KNNLN-Er ceramics show the coexistence of orthorhombic and tetragonal structures. The grain size increases obviously and then decreases slightly with the holding time increasing. The KNNLN-Er ceramics exhibit good piezoelectric performance (piezoelectric constant d 33 ∼97 pC/N, electromechanical couple coefficient k t ∼0.36) and the moderate transparency of 34% when the holding time is 6h during sintering at 1120°C. Besides, the intensity of the photoluminescence emission spectra increases with the holding time increasing. Furthermore, in order to estimate the properties of the KNNLN-Er transparent ceramics, an ultrasonic transducer with a center frequency of 10.5 MHz was fabricated, which can be used for photoacoustic and fluorescence imaging. The results indicate that the KNNLN-Er ceramics have potential for multimode imaging applications. [ABSTRACT FROM AUTHOR]

Photoacoustic microscopy (PAM), due to its deep penetration depth and high contrast, is playing an increasingly important role in biomedical imaging. PAM imaging systems equipped with conventional ultrasound transducers have demonstrated excellent imaging performance. However, these opaque ultrasonic transducers bring some constraints to the further development and application of PAM, such as complex optical path, bulky size, and difficult to integrate with other modalities. To overcome these problems, ultrasonic transducers with high optical transparency have appeared. At present, transparent ultrasonic transducers are divided into optical-based and acoustic-based sensors. In this paper, we mainly describe the acoustic-based piezoelectric transparent transducers in detail, of which the research advances in PAM applications are reviewed. In addition, the potential challenges and developments of transparent transducers in PAM are also demonstrated. [ABSTRACT FROM AUTHOR]

Transcranial focused ultrasound (tFUS) is increasingly used in experimental neuroscience due to its neuromodulatory effectiveness in animal studies. However, achieving multitarget tFUS in small animals is typically limited by transducer size, energy transfer efficiency, and brain volume. The objective of this work was to construct an ultrasound system for multitarget neuromodulation in small animals. First, a miniaturized high-powered 2-D array transducer was developed. The phase delay of each array element was calculated based on the multifocal time-reversal method, generating multiple foci simultaneously in a 3-D field. The effects of the axial focal length, interfocus spacing (lateral distance between the two focal centers), and the number of foci on the focal properties of the pressure field were examined through numerical simulations. In-vitro ultrasonic measurements and transcranial simulations on a rat skull were conducted. The minimum interfocus spacing separating two −6-dB foci and the peak full-width at half-maximum were positively correlated with axial focal length; the relative relationship between the interfocus spacing and pressure field properties was similar for each axial focal length. The maximum acoustic pressure and spatial average intensity at focus in deionized water were 2.21 MPa and 133 W/cm2, respectively. The simulated and experimental results were compared, demonstrating agreement in both peak position and focus shape. The ultrasound system can provide a neuroscientific platform for evaluating the feasibility of multitarget ultrasound stimulation treatment protocols, thus improving the understanding of functional neuroanatomy. [ABSTRACT FROM AUTHOR]

Transcranial ultrasound therapy has become a noninvasive method for treating neurological and psychiatric disorders, and studies have further demonstrated that multitarget transcranial ultrasound therapy is a better solution. At present, multitarget transcranial ultrasound therapy in small animals can only be achieved by the multitransducer or phased array. However, multiple transducers may cause spatial interference, and the phased array system is complicated, expensive, and especially unsuitable for small animals. This study is the first to design and fabricate a miniature acoustic holography lens for multitarget transcranial ultrasound therapy in rats. The acoustic holographic lens, working at a frequency of 1.0 MHz, with a size of 10.08 mm $\times10.08$ mm and a pixel resolution of 0.72 mm, was designed, optimized, and fabricated. The dual-focus transcranial ultrasound generated based on the lens was measured; the full-width at half-maximum (FWHM) of the focal spots in the ${y}$ -direction was 2.15 and 2.27 mm and in the ${z}$ -direction was 2.3 and 2.36 mm. The focal length was 5.4 mm, and the distance between the two focuses was 5.6 mm, close to the desired values of 5.4 and 6.0 mm. Finally, the multiple-target blood–brain barrier opening in rats’ bilateral secondary visual cortex (mediolateral area, V2ML) was demonstrated using the transcranial ultrasound therapy system based on the lens. These results demonstrate the good performance of the multitarget transcranial ultrasound therapy system for small animals, including high spatial resolution, small size, and low cost. [ABSTRACT FROM AUTHOR]

Background: Histologic studies have demonstrated that lipid content and its spatial distribution is related to plaque vulnerability. However, in vivo imaging is still limited. Photoacoustic imaging may provide novel in vivo insights into these lipid-rich plaques. Objectives: This study sought to examine whether intravascular photoacoustic tomography (IVPAT) allows localization and quantification of lipid content in atherosclerotic plaques. Methods: Rabbits fed with a high-fat/high-cholesterol diet served as the atherosclerotic model. Catheter-based IVPAT was used to evaluate pixel-based lipid relative concentration (LRC) of the vessel wall. The aorta of 4 groups of rabbits (n = 12) were examined ex vivo with IVPAT after 0, 5, 10, and 15 weeks of a high-fat diet, respectively. Six rabbits underwent 3-dimensional (3D) IVPAT after 20 weeks of the high-fat diet. Three rabbits were examined in vivo using IVPAT without interruption of blood flow. Concentration-based lipid map and quantitative index were calculated. For subsequent histologic correlation, all specimens were evaluated with Oil Red O staining. Results: Cross-sectional LRC maps allowed visualization of concentration and depth information of lipid content in the atherosclerotic plaques. Lipid accumulation within plaque, assessed by the maximum LRC, mean LRC, and high lipid content area correlated to duration of a high-fat diet. Three-dimensional LRC maps enabled overall evaluation of focal plaques in an intact explanted aorta including spatial and structural features. In vivo-obtained LRC maps accurately showed the structure of lipid core with high contrast. Ex vivo and in vivo IVPAT results were highly consistent with histological results. Conclusions: In an animal model, IVPAT allowed characterization of spatial and quantitative features of lipid-rich plaques. [ABSTRACT FROM AUTHOR]

X-ray-induced acoustic computed tomography (XACT) is a unique hybrid imaging modality that combines high X-ray absorption contrast with high ultrasonic resolution. X-ray radiography and computerized tomography (CT) are currently the gold standards for 2-D and 3-D imaging of skeletal tissues though there are important properties of bone, such as elasticity and speed of sound (SOS), that these techniques cannot measure. Ultrasound is capable of measuring such properties though current clinical ultrasound scanners cannot be used to image the interior morphology of bones because they fail to address the complicated physics involved for exact image reconstruction; bone is heterogeneous and composed of layers of both cortical and trabecular bone, which violates assumptions in conventional ultrasound imaging of uniform SOS. XACT, in conjunction with the time-reversal algorithm, is capable of generating precise reconstructions, and by combining elements of both X-ray and ultrasound imaging, XACT is potentially capable of obtaining more information than any single of these techniques at low radiation dose. This article highlights X-ray-induced acoustic detection through linear scanning of an ultrasound transducer and the time-reversal algorithm to produce the first-ever XACT image of a bone sample. The results of this study should prove to enhance the potential of XACT imaging in the evaluation of bone diseases for future clinical use. [ABSTRACT FROM AUTHOR]

In this study, we propose an integrated approach which combines 3D printing and liquid precursor infiltration together to prepare alumina-toughened zirconia (ATZ) composite. Controllable manipulation of the microstructure of the composite could be realized through different infiltration times and sintering temperature. The 3D-printed ATZ with infiltration and post-CIP sintered at 1550 °C possesses the highest relative density (98.11%), hardness (12.65 ± 0.24 GPa) and fracture toughness (6.42 ± 0.33 MPa m1/2). The rates of increase in the performance compared with the undoped zirconia sintered at 1550 °C are 1.8%, 8.4% and 34.6%, respectively. The dominated toughening mechanism of ATZ could be attributed to the effect of Al2O3 inclusion on crack deflection and energy absorption. The 3D-printed ATZ sample with infiltration followed by CIP sintered at 1550 °C shows the lowest aging rate and the lowest phase transformation depth compared with 3Y-TZP (Tetragonal Zirconia Polycrystal). Our integrated approach could not only realize the complex and ultrafine shape free of molds, but also suppress the low temperature aging behavior of dental implants, which has baffled dentists for a long time. [ABSTRACT FROM AUTHOR]

Abstract The PZT ceramics with different weight content from 78% to 89% were printed using the stereolithography method. The piezoelectric properties as well as the microstructure of the ceramics were investigated in detail. X-ray patterns and Raman spectra demonstrate that the steady PZT tetragonal phase has already formed in these sintered ceramics. Besides, the piezoelectric constant and dielectric constant were 212–345 pC/N and 760–1390, which were sligthly lower than that of the dry pressing disk. Furthermore, a two-dimensional ultrasound transducer array (8 × 8) was designed and developed to evaluate the properties of the 3D-printed PZT ceramics. [ABSTRACT FROM AUTHOR]

In this work, a stereolithography-based method of 3D printing was successfully used to fabricate a complex-shaped triangular zirconia cutting tool with a tool withdrawal groove and a honeycomb ceramic component. The sintered bodies displayed significant shrinkage after sintering, with the maximum shrinkage being 35.26%. The XRD pattern indicated that the crystalline phase of the parts was the t-ZrO 2 phase, while SEM characterization revealed that the sintered bodies were composed of densely packed submicron-grade grains, without any discernible pores. The density of the parts was measured as 97.14% via Archimedes’ water displacement method, which is consistent with the results of SEM characterization. Additionally, the measured Vickers hardness and fracture toughness of the fabricated parts were 13.0597 GPa and 6.0380 MPa m 1/2 , respectively. These values are close to the structural properties of common zirconia ceramics prepared by conventional approaches. Hence, a novel DLP-stereolithography-based 3D printing process for the fabrication of complex and dense zirconia ceramic parts has been proposed in this work. [ABSTRACT FROM AUTHOR]

Ultrasonic is one of the well-known methods for surface roughness measurement, but small roughness will only lead to a subtle variation of transmission or reflection. To explore sensitive techniques for surfaces with small roughness, nonlinear ultrasonic measurement in through-transmission and pulse-echo modes was proposed and studied based on an effective unit-cell finite element (FE) model. Higher harmonic generation in solids was realized by applying the Murnaghan hyperelastic material model. This FE model was verified by comparing the absolute value of the nonlinearity parameter with the analytical solution. Then, random surfaces with different roughness values ranging from 0 μm to 200 μm were repeatedly generated and studied in the two modes. The through-transmission mode is very suitable to measure the surfaces with roughness as small as 3% of the wavelength. The pulse-echo mode is sensitive and effective to measure the surface roughness ranging from 0.78% to 5.47% of the wavelength. This study offers a potential nondestructive testing and monitoring method for the interfaces or inner surfaces of the in-service structures. [ABSTRACT FROM AUTHOR]