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.

Microwave-induced thermoacoustic (TA) imaging is efficient in detecting anomalous absorption areas, especially breast tumors. The operation of previous imaging systems has generally suffered from complexity, and early-stage tumors could be missed because of signal loss. In this paper, we report a variable-curvature and multi-dimensional screening method realized by combining a redesigned adaptive algorithm and an integrated TA breast screening system (ITBCS) comprising a flexible detector and a traction device designed for multi-axis rotation. In contrast to conventional TA imaging systems, the proposed system improves the ability to identify early-stage breast tumors, with a simplified system and operational process. Variable curvature is achieved by the flexible characteristics of the detector, which achieves good shape adaptation between the tissue and the detector. Moreover, multi-dimensional scanning is achieved by the multi-axis traction device and meets the requirements for angle transformation and dynamic imaging. The experimental results indicate that ITBCS exhibits a good performance in detecting breast tumors. Faster screening makes inspection more efficient, thereby improving clinical applicability and providing a convenient facility for large-scale physical examination.

No abstract