Abstract
All-optical ultrasound imaging, where ultrasound is generated and detected using light, has recently been demonstrated as a viable modality that is inherently insensitive to electromagnetic interference and exhibits wide bandwidths. High-quality 2D and 3D all-optical ultrasound images of tissues have previously been presented; however, to date, long acquisition times (ranging from minutes to hours) have hindered clinical application. Here, we present the first all-optical ultrasound imaging system capable of video-rate, real-time two-dimensional imaging of biological tissue. This was achieved using a spatially extended nano-composite optical ultrasound generator, a highly sensitive fibre-optic acoustic receiver, and eccentric illumination resulting in an acoustic source exhibiting optimal directivity. This source was scanned across a one-dimensional source aperture using a fast galvo mirror, thus enabling the dynamic synthesis of source arrays comprising spatially overlapping sources at non-uniform source separation distances. The resulting system achieved a sustained frame rate of 15 Hz, a dynamic range of 30 dB, a penetration depth of at least 6 mm, a resolution of 75 µm (axial) by 100 µm (lateral), and enabled the dynamics of a pulsating ex vivo carotid artery to be captured.
Highlights
All-optical ultrasound is an emerging imaging modality that shows great promise for biomedical imaging
Compared to conventional electronic systems comprising piezoelectric or capacitive ultrasound transducer elements, optical transducers have been shown to yield similar or higher pressures and bandwidths [2, 4, 10, 15,16,17,18]. When such an optical acoustic source is paired with an optical acoustic receiver, reflected acoustic waves can be captured with an all-optical pulse-echo transducer element that contains no electronics, and is MRI compatible and immune to electromagnetic interference
We present a new paradigm for all-optical ultrasound imaging that enables real-time, video-rate 2D ultrasound imaging at a frame rate of 15 Hz
Summary
All-optical ultrasound is an emerging imaging modality that shows great promise for biomedical imaging. Compared to conventional electronic systems comprising piezoelectric or capacitive ultrasound transducer elements, optical transducers have been shown to yield similar or higher pressures and bandwidths [2, 4, 10, 15,16,17,18]. When such an optical acoustic source is paired with an optical acoustic receiver, reflected acoustic waves can be captured with an all-optical pulse-echo transducer element that contains no electronics, and is MRI compatible and immune to electromagnetic interference. For in vivo biomedical imaging, these times need to be decreased by several orders of magnitude to capture dynamic processes in the presence of physiological motion
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