In this study, we have developed an acoustic radiation force orthogonal excitation optical coherence elastography
(ARFOE-OCE) method for the visualization of the shear wave and the calculation of the shear modulus based on the OCT
Doppler variance method. The vibration perpendicular to the OCT detection direction is induced by the remote acoustic
radiation force (ARF) and the shear wave propagating along the OCT beam is visualized by the OCT M-scan. The
homogeneous agar phantom and two-layer agar phantom are measured using the ARFOE-OCE system. The results show
that the ARFOE-OCE system has the ability to measure the shear modulus beyond the OCT imaging depth. The OCT
Doppler variance method, instead of the OCT Doppler phase method, is used for vibration detection without the need of
high phase stability and phase wrapping correction. An M-scan instead of the B-scan for the visualization of the shear
wave also simplifies the data processing.
High-resolution elasticity mapping of tissue biomechanical properties is crucial in early detection of many diseases. We report a method of acoustic radiation force optical coherence elastography (ARF-OCE) based on the methods of vibroacoustography, which uses a dual-ring ultrasonic transducer in order to excite a highly localized 3-D field. The single element transducer introduced previously in our ARF imaging has low depth resolution because the ARF is difficult to discriminate along the entire ultrasound propagation path. The novel dual-ring approach takes advantage of two overlapping acoustic fields and a few-hundred-Hertz difference in the signal frequencies of the two unmodulated confocal ring transducers in order to confine the acoustic stress field within a smaller volume. This frequency difference is the resulting “beating” frequency of the system. The frequency modulation of the transducers has been validated by comparing the dual ring ARF-OCE measurement to that of the single ring using a homogeneous silicone phantom. We have compared and analyzed the phantom resonance frequency to show the feasibility of our approach. We also show phantom images of the ARF-OCE based vibro-acoustography method and map out its acoustic stress region. We concluded that the dual-ring transducer is able to better localize the excitation to a smaller region to induce a focused force, which allows for highly selective excitation of small regions. The beat-frequency elastography method has great potential to achieve high-resolution elastography for ophthalmology and cardiovascular applications.