Microwave-induced thermoacoustic imaging (TAI) is a noninvasive modality based on the differences in microwave absorption of various biological tissues. TAI has been extensively researched in recent years, and several studies have revealed that TAI possesses advantages such as high resolution, high contrast, high imaging depth and fast imaging speed. In this paper, we reviewed the development of the TAI technique, its excitation source, data acquisition system and biomedical applications. It is believed that TAI has great potential applications in biomedical research and clinical study.

Microwave-induced thermoacoustic imaging (MTAI) utilizes the high dielectric contrast of tissues in the microwave range, and, combined with the high resolution of ultrasound imaging, can noninvasively obtain anatomical and functional structure information.

Purpose: To investigate the feasibility of microwave-induced thermoacoustic imaging (MTAI) in detecting small pancreatic tumors (< 10 mm in diameter) and to complement the limitation of current clinical imaging methods. Methods: A home-made MTAI system composed of a portable antenna and pulsed microwave generator was developed. The thermoacoustic nanoparticles were composed of the galectin-1 antibody for targeting pancreatic tumors and Fe 3 O 4 nanoparticles as microwave absorbers (anti-Gal1-Fe 3 O 4 nanoparticles). The microwave absorption properties of the nanoparticles were measured with a vector network analyzer and the resolving power of MTAI was investigated by imaging excised pancreatic tumors of different sizes (diameters of 1.0 mm, 3.1 mm, 5.0 mm, 7.2 mm). To simulate actual imaging scenarios, an in vivo heterozygosity model was constructed by covering the pancreatic tumors (~ 3 mm in diameter) in BALB/c nude mice with biologic tissue (~ 5 cm in depth). MTAI images of the heterozygosity model were acquired with/without the injection of the anti-Gal1-Fe 3 O 4 nanoparticles and the thermoacoustic contrast from pancreatic tumors was evaluated with Student's paired t test. The data were analyzed with analysis of variance and nonparametric statistics. Results : Following intravenous infusion, anti-Gal1-Fe 3 O 4 nanoparticles efficiently accumulated in the tumor. The MTAI contrast enhancement in pancreatic tumors with anti-Gal1-Fe 3 O 4 nanoparticles was verified in vitro and in vivo . The pancreatic tumors were visible in nude mice examined with MTAI with a mean contrast enhancement ratio of 2.3 ± 0.15 (standard error of the mean) ( P =. 001) at 6 h post-injection of the nanoparticles. MTAI identified tiny pancreatic tumors in deep tissues with high fidelity. Conclusion : MTAI offers deep imaging depth and high contrast when used with anti-Gal1-Fe 3 O 4 nanoparticles. It can identify pancreatic tumors smaller than 5 mm, which is beyond the identification limit size (~10 mm) of other nondestructive clinical imaging methods. Thus, MTAI has great potential as an alternative imaging modality for early pancreatic cancer detection.

Structural features and microwave dielectric properties of (1−x)(Sr 0.3 Ca 0.427 Nd 0.182 )TiO 3−x SmAlO 3 (0.05 ≤ x ≤ 0.4) ceramics were investigated. X-ray diffraction patterns illustrated that solid solutions with the orthorhombic perovskite were shown to be formed in the ranges of 0.05 ≤ x ≤ 0.4. Moreover, the dielectric constant (ε r ) of sintered ceramics had a quasi-linear decrease with the increase in SmAlO 3 content. A certain amount of Sm and Al substitution for A-and B-sites could substantially improve the quality factor (Qf ) of the ceramics. Increasing the oxygen octahedral distortion led to a decrease in the temperature coefficient of the resonant frequency (τ f ) from 216.3 to −34.8 ppm • C −1 . Additionally, optimized microwave dielectric properties can be achieved for the specimens using 0.75(Sr 0.3 Ca 0.427 Nd 0.182 )TiO 3 -0.25SmAlO 3 ceramics [ε r ∼ 58.3, Qf ∼ 18800 GHz (at 4.65 GHz) and τ f ∼ 2.3 ppm • C −1 ] after being sintered at 1500 • C for 4 h. Keywords. (Sr 0.3 Ca 0.427 Nd 0.182 )TiO 3 ; SmAlO 3 ; microwave dielectric properties; oxygen octahedral distortion.

The [Bi0.5(Na0.82K0.18)0.5]1-xLaxTi1-yZryO3 (BNKLZT) energy storage ceramics were prepared by conventional solid-state reaction method. Structure, surface morphology, dielectric, ferroelectric and energy storage properties of the BNKLBZT ceramics were investigated. The BNKLZT ceramics showed perovskite, homogeneous and dense structure. Grain size was coarsened by Zr doping, and refined by La doping. Low remnant polarization (Pr) and coercive field (Ec), slim P-E loops were obtained by introducing La and Zr dopants. The optimum energy storage property was obtained for the composition of La=0.03 and Zr=0.03, with energy storage density of 0.84 J/cm3 at 80 kV/cm.