Air-coupled ultrasound based noncontact reverberant optical coherence elastography

Reverberant optical coherence elastography (Rev-OCE) has been used to map the mechanical properties of tissues with high quality and resolution regardless of tissue boundaries and stiffness.Generally, Rev-OCE utilizes the interference of multiple arbitrary mechanical waves generated by distinct sources in direct contact with the sample.In this study, a novel methodology was designed and implemented to create a completely noncontact method utilizing multiple air-coupled ultrasound (ACUS) transducers capable of generating a reverberant field within the sample.An array of unfocused ACUS transducers with a resonant frequency of 40 kHz was characterized and placed in a 3D-printed ring to produce a reverberant field in a side-by-side gelatin phantom (4% and 8% w/w gelatin concentration).The results showed the generation of a reverberant field within the sample with a transverse resolution of 208.8 72.4 m.Also, this method was tested in porcine cornea showing the stiffness differences found in the corneal layers, where the wave speed is substantially higher in the epithelium (3.7 m/s) and anterior stroma regions compared with the posterior and endothelium regions (2.2 m/s).The generation of a reverberant field using ACUS Rev-OCE guarantees the integrity of sensitive samples, and it shows its potential to be used in-vivo without causing any damage or discomfort in live subjects.