All-optical ultrasound imaging, in which ultrasound is generated and received using light, is well-suited to minimally invasive surgical procedures. Here we present a device that can provide real-time M-mode ultrasound images, and demonstrate its use imaging a dynamic heart valve phantom. This device, comprising two optical fibres, one with a graphene-polydimethylsiloxane composite coating for ultrasound generation, and a second with a concave Fabry-Perot cavity for ultrasound reception, had a diameter of < 1 mm. This provided a wide ultrasound transmission bandwidth (> 30 MHz) that enabled imaging with high axial resolution (< 50 μm) and large imaging depths (> 2 cm). M-mode imaging with an A-line rate of 100 Hz was demonstrated on a heart valve phantom with realistic mitral valve motion. This work demonstrates the potential for all-optical ultrasound imaging to be used for guidance of intracardiac interventions.
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