The piezoelectric materials, such as ceramics, crystals, and films, have wide applications in the mechanical industry, medical imaging, electronic information, and ultrasonic devices, etc. Generally, adding oxide dopants, or introducing new solid solutions to form the morphotropic phase boundary of the piezoelectric materials were common strategies to enhance the electric properties. In recent decades, rare-earth elements doped piezoelectric materials have attracted much attention due to their multifunctional performances combining piezoelectric and photoluminescence properties, which has potential applications in ultrasonics, electronics, automatic control, machinery and optoelectronic fields. An overview of the recent investigations and perspectives on rare-earth doped piezoelectric ceramics, single crystals, and films were presented.

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.

Objective. Exhaustion of Serotonin (5-hydroxytryptamine, 5-HT) is a typical cause of the depression disorder’s development and progression, including depression-like behaviors. Transcranial ultrasound stimulation (TUS) is an emerging non-invasive neuromodulation technique treating various neurodegenerative diseases. This study aims to investigate whether TUS ameliorates depression-like behaviors by restoring 5-HT levels. Methods. The depression model mice are established by chronic restraint stress (CRS). Ultrasound waves (FF = 1.1 MHz, PRF = 1000 Hz, TBD = 0.5 ms, SD = 1 s, ISI = 1 s, and DC = 50%) were delivered into the dorsal raphe nucleus (DRN) for 30 min per day for 2 weeks. Depression-like behavior changes are evaluated with the sucrose preference and tail suspension tests. Liquid chromatography–mass spectrometry is performed to quantitatively detect the concentration of 5-HT in the DRN to explore its potential mechanism. The effectiveness and safety of TUS were assessed by c-Fos immunofluorescence and hematoxylin and eosin (HE) staining, respectively. Results. Three weeks after CRS, 22 depressive mice models were screened by sucrose preference index (SPI). After 2 weeks of ultrasound stimulation of the DRN (DRN-TUS) in depressive mice, the SPI was increased ( p = 0.1527) and the tail suspension immobility duration was significantly decreased ( p = 0.0038) compared with the non-stimulated group. In addition, TUS significantly enhances the c-Fos ( p = 0.05) positive cells’ expression and the 5-HT level ( p = 0.0079) in the DRN. Importantly, HE staining shows no brain tissue damage. Conclusion. These results indicate that DRN-TUS has safely and effectively improved depression-like behaviors including anhedonia and hopelessness, potentially by reversing the depletion of 5-TH. Significance TUS may provide a new perspective on depression therapy, possibly through restoring monoamine levels.

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.