Two-dimensional tissue imaging by use of parallel detection of ultrasound-modulated laser speckles

Ultrasound-modulated optical tomography in biological tissue was studied. An ultrasonic beam was focused into a biological tissue sample to modulate the laser light passing through the ultrasonic beam inside the tissue. The speckle field formed by the transmitted laser light was detected by a CCD camera with the source-synchronous-illumination lock- in technique. The ultrasound-modulated laser light reflects the local optical and mechanical properties within the ultrasonic beam and can be used for tomographic imaging of the tissue. We implemented frequency-swept modulation to obtain spatial resolution along the ultrasonic axis. 2D images of biological tissue were successfully obtained with both single frequency modulation and frequency-swept modulation. 3D images could be acquired as well in principle.