First assessment of thermoacoustic tomography for in vivo detection of rheumatoid arthritis in the finger joints detection of rheumatoid arthritis in the finger joints

Background The diagnosis of rheumatoid arthritis (RA) is complicated because of the complexity of symptoms and joint structures. Current clinical imaging techniques for the diagnosis of RA have strengths and weaknesses. Emerging imaging techniques need to be developed for the diagnosis or auxiliary diagnosis of RA. Purpose This study aimed to demonstrate the potential of thermoacoustic tomography (TAT) for in vivo detection of RA in the finger joints. Methods Finger joints were imaged by a TAT system using three different microwave illumination methods including pyramidal horn antenna, and parallel in‐phase and anti‐phase microwave illuminations. Both diseased and healthy joints were imaged and compared when the three microwave illumination methods were used. Magnetic resonance imaging (MRI) of all the joints was performed to validate the TAT findings. In addition, two diseased joints were imaged at two time points by the pyramidal horn antenna‐based TAT to track/monitor the progression of RA during a time period of 16 months. Three‐dimensional (3‐D) TAT images of the joints were also obtained. Results The TAT images of the diseased joints displayed abnormalities in bone and soft tissues compared to the healthy ones. The TAT images by pyramidal horn antenna and in‐phase microwave illumination showed high similarity in image appearance, while the anti‐phase‐based TAT images provided different information about the disease. We found that the TAT findings matched well with the MRI images. The 3‐D TAT images effectively displayed the stereoscopic effect of joint lesions. Finally, it was evident that TAT could detect the development of the lesions in 16 months. Conclusion TAT can noninvasively visualize bone lesions and soft tissue abnormalities in the joints with RA. This first in vivo assessment of TAT provides a foundation for its clinical application to the diagnosis and monitoring of RA in the finger joints.