Shear wave elastography method combining phase-sensitive optical coherence tomography and coded acoustic radiation force

We combined phase-sensitive optical coherence tomography (PhS-OCT) and acoustic radiation force (ARF) to develop a shear wave elastography (SWE) method that could be used for ophthalmic applications. SWE measures tissue stiffness from the speed of shear waves propagating through tissue. Assessing the elastic properties of the cornea and the intraocular lens can, for example, help the management of refractive surgeries (myopia or presbyopia correction). OCT is a non-contact imaging method easily applicable in vivo that provides micron-scale resolution particularly suitable for characterizing ocular tissues. ARF is commonly used to remotely induce shear waves in tissue by emitting short (~100 μs) focused ultrasound pulses. To increase the signal-to-noise ratio (SNR) of detected shear waves, we used a pulse compression method in which the instantaneous peak energy is spread over long (several ms) coded emissions and the detected signal is digitally compressed into a short pulse to increase both SNR and spatio-temporal resolution. The post-compression displacements were used to reconstruct maps of the shear wave speed in gelatin phantoms. We demonstrated the feasibility of using PhS-OCT and ARF to perform elastography at low acoustic pressures (1.5 MPa) owing to the high SNR provided by pulse compression. Future work will focus on implementing this technique for ocular tissues and investigating potential clinical applications.