Publication

Abstract : In ultrasound assisted optical elastography (UAOE) the amplitude of vibration inside the object introduced by an ultrasound (US) beam is read out by a coherent light beam. The measurement is the depth of modulation in the intensity autocorrelation of light that intercepted the insonified region and detected at the boundary. It is observed that the measured depth of modulation is owing to refractive index modulation and scattering coefficient modulation, in addition to the tissue-particle vibration. Since elasticity is measured from the amplitude of vibration it is essential to characterize and separate the contribution to the modulation from refractive index and scattering coefficient modulations. In this work we report the contribution of the scattering coefficient modulation in the insonified region to the measured modulation in the autocorrelation. We found through simulation studies that the contribution from scattering coefficient is small compared to the vibration. In addition, this contribution becomes smaller as the stiffness in the region increases. We also provide a means of quantifying this contribution so that the effect of vibration amplitude can be separated from the overall measured modulation depth.