Frequency-swept ultrasound-modulated optical tomography of scattering media

A novel frequency-swept ultrasound-modulated optical tomography technique was developed to image scattering media. A frequency-swept ultrasonic wave was used to modulate the laser light passing through a scattering medium. The modulated light was received by an optical detector and was heterodyned with a reference frequency sweep. The heterodyned signal was recorded in the time domain and was then analyzed in the frequency domain to yield a one-dimensional image along the ultrasonic axis. Multiple one-dimensional images obtained at various positions perpendicular to the ultrasonic axis were combined to yield a two-dimensional tomographic image of the medium.