Ring-shaped light illumination ultrasound-modulated optical tomography and its application for sentinel lymph node mapping ex vivo

We have succeeded in implementing ring-shaped light illumination ultrasound-modulated optical tomography (UOT) in both transmission and reflection modes. These systems used intense acoustic bursts and a charge-coupled device camera-based speckle contrast detection method. By mounting an ultrasound transducer into an optical condenser, we can combine the illuminating light component with the ultrasound transducer. Thus, the UOT system is more clinically applicable than previous orthogonal mode systems. Furthermore, we have successfully imaged an ex vivo methyleneblue-dyed sentinel lymph node (SLN) embedded deeper than 12 mm, the mean depth of human sentinel lymph nodes, in chicken breast tissue. These UOT systems offer several advantages: noninvasiveness, nonionizing radiation, portability, cost-effectiveness, and possibility of combination with ultrasound pulse-echo imaging and photoacoustic imaging. One potential application of the UOT systems is mapping SLNs in axillary staging for breast cancer patients.