Rapid Non-Contact Optical Ultrasound for Biomedical Imaging

Biomedical ultrasound imaging is typically performed using electronic transducer technology, which results in imaging probes exhibiting large mechanical footprints that require physical contact with the imaging target. While this mature technology allows for high-quality, versatile free-hand imaging, its applicability is limited in crowded surgical settings and scenarios at risk of infection or trauma. Instead, here a novel system is presented that enables non-contact ultrasound imaging through remote sensing. This is achieved using light rather than electronics to both generate and detect ultrasound, which is delivered in free-space to the surface of the object by weakly-focussed beams. To maximise the signal fidelity, a custom membrane was developed that is deposited to the surface of the imaging target. The combined system and membrane currently achieve real-time and dynamic imaging at a frame rate of up to 22 Hz for highly reflective targets, and requires an acquisition time of ca. 27 s for physiologically relevant phantoms. As such, the system already achieves clinically relevant performance for, e.g., needle or instrument tracking, and various improvements are suggested that in the near future will significantly accelerate image acquisition of soft tissue – ultimately resulting in sub-second biomedical non-contact ultrasound imaging.