Sustained real-time and video-rate interventional optical ultrasound imaging

Minimally invasive surgery offers improved recovery times and reduced complication risk compared with open surgery. However, effective image acquisition probes suitable for deployment in clinical workflows are key to the success of such procedures. Fiber-optic optical ultrasound (OpUS) offers strong potential for interventional image guidance due to its small lateral probe dimensions and high imaging resolution, but to date, such miniature imaging probes have only yielded M-mode (single image line) or still images.

Here, we present a motorized actuation approach to fiber-optic interventional OpUS imaging that enables sustained and video-rate imaging while retaining its small form factor.

A fabrication method utilizing a commercial laser cutter is presented that yields partially forward-emitting OpUS sources ideally suited for interventional image guidance. These transmitters were incorporated into a miniature imaging probe with a width of just $600\mu m$ (1.8 mm with protective encapsulation) and combined with a linear actuator to synthesize an imaging aperture at the distal end of the probe through manipulation at its proximal end.

The presented imaging paradigm achieved real-time, two-dimensional OpUS imaging at frame rates of up to 7 Hz and was capable of high-resolution imaging ( $94\mu m$ axial and $241\mu m$ lateral). The imaging performance of the presented imaging system was assessed using various imaging phantoms, and its clinical suitability was confirmed by emulating endobronchial OpUS imaging through a commercial bronchoscope.

These results constitute the first-ever sustained, real-time dynamic imaging using a side-viewing single-element OpUS probe via rapid actuation, which enables a wide range of applications in minimally invasive surgical guidance.