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. Author manuscript; available in PMC: 2017 Jul 1.
Published in final edited form as: IEEE J Sel Top Quantum Electron. 2015 Dec 17;22(4):6802816. doi: 10.1109/JSTQE.2015.2505147

Fig. 4.

Fig. 4

Spectroscopic and shear-wave MM-OCE. (a, b) Spectroscopic MM-OCE is an alternative way of determining the resonant/natural frequency. (a) Excited by a chirp waveform, a cylindrical agarose sample exhibits (top) a frequency-dependent displacement, where (middle) the computed amplitude reveals the longitudinal resonance modes n =1,2,3,4, and (bottom) the phase shift from 0 to π across each resonance mode agrees with theoretical expectation [72]. (b) Spectroscopic MM-OCE with a two-dimensional imaging scheme was applied to probe the biomechanical properties of the sample both spatially and temporally, where the mechanical spectral response can be revealed in both (I, II) homogenous rat muscle and lung tissues and (III, IV) more heterogeneous tissues such as at the tumor-adipose margin in human breast tissue. (IV) A stronger MM-OCT signal is seen at lower excitation frequencies for softer tissue and at higher frequencies for the stiffer areas (tumor) [75]. (c) Shear wave MM-OCE shown in (I) a heterogeneous agarose sample where a clear boundary between stiff and soft regions can be seen. (II) The wave propagation can be visualized and further used for (III) Young's moduli quantification and mapping [74].