Purpose Conventional antenna used in thermoacoustic imaging (TAI) is often bulky, making it difficult to translate TAI from the bench to the clinic. In this paper, we proposed a handheld dipole antenna which will be a good candidate for the construction of a compact TAI system. Methods Here, we propose a TAI system based on a handheld dipole antenna with an aperture of 6 cm and a weight of 230 g. Compensation of the electric field attenuation for such a system was also investigated. Results Compared to the conventional open‐ended waveguide and pyramidal horn antenna used in TAI, our results reveal that the electric field attenuation induced distortion is effectively reduced by using the attenuation factor 1/r2 for compensation and that the handheld dipole antenna provides the highest efficiency of microwave delivery. Conclusions This study suggests that the handheld dipole antenna has the potential to be utilized for the construction of a compact TAI system, making TAI more suitable for preclinical and clinical applications.

Purpose Thermoacoustic tomography (TAT) has been studied to image joints. While several joint tissues could be thermoacoustically imaged, tendons and bone could not be recovered completely or clearly. The purpose of this study was to overcome this limitation. Methods We developed a novel TAT system based on anti‐phase microwave illumination method to image the proximal interphalangeal joint and middle phalanx of a right middle finger from a healthy volunteer. The performance of this new system for imaging joints and tendons was compared with that by in‐phase microwave illumination and a conventional pyramidal horn antenna. Results Anti‐phase microwave illumination can produce relatively homogeneous electric (E)‐Field distributions inside the joint tissues. The homogeneous E‐Field distributions can enhance the detectability of flexor tendon and extensor tendon. Anti‐phase microwave illumination could image the flexor tendon, and extensor tendon and bone, which were not clearly imaged by the in‐phase microwave illumination or by the horn antenna. The images generated by the in‐phase microwave illumination and pyramidal horn antenna were almost identical in terms of the tissue types they imaged. Conclusions Anti‐phase illumination can overcome the limitation associated with the conventional TAT by adding the ability of completely delineating tendons and bone in the joints. This study paves the way for us to continue the study and to validate its utility in detection of joint diseases.

We present a method that allows for hybrid microwave-excited thermoacoustic and ultrasound (HMTAU) imaging without an additional ultrasound transmitting circuitry. The same microwave pulse is used to simultaneously generate thermoacoustic (TA) signals from the sample by the thermoacoustic effect, and ultrasound (US) signals from the piezoelectric transducer by the inverse piezoelectric effect. The same transducer collects the US signals reflected from the sample as a result of the US pulse (pulse-echo) and the TA signals as a result of the sample absorbing microwaves. Experiments are conducted to show how the microwave pulse-width significantly impacts the excitation efficiency of ultrasonic waves, which can reduce the requirement for microwave power. We found that the mechanical response of the US transducer to this transient expansion shows a maximum if the pulse-width of the microwave is close to half of the center period of the US transducer. We also use phantom experiments to demonstrate the complementary contrast mechanisms of the two modalities. The results obtained indicate that our method offers the potential of a low-cost dual-modality technique for noninvasive biomedical imaging.