Technical Note: Anti-phase microwave illumination-based thermoacoustic tomography of in vivo human finger joints.

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.