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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/cm 2 , 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.

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.

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]

In this work, Pb(InNb)O-Pb(MgNb)O-PbTiO (PIN-PMN-PT) single crystal/epoxy 1-3 composites with different thicknesses (400 μm to 825 μm) were fabricated using the conventional dice-and-fill method. Their properties were compared with the corresponding lead zirconate titanate (PZT) ceramic 1-3 composites. Excellent properties for ultrasonic transducer applications have been achieved, such as high electromechanical coupling coefficient ( k ≈ 78% to 83%), high piezoelectric strain coefficient ( d ≈ 1000 pm/V), and lower acoustic impedance ( Z ≈ 20 Mrayl). The strain levels of PIN-PMN-PT composites were almost constant (1000 pm/V) with decreasing thickness, being much higher than those of PZT composites (650 pm/V). However, an increase in strain hysteresis was observed with decreasing thickness, reaching 25.3% for the 400- μm single-crystal 1-3 composite, which is lower than the corresponding PZT composites (44.1% for 350- μm PZT ceramic 1-3 composite). These results show that PIN-PMN-PT single-crystal 1-3 composites have great potential for use in advanced ultrasound transducer applications. [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]