{Reference Type}: Journal Article
{Title}: Through-needle all-optical ultrasound imaging in vivo: a preclinical swine study.
{Author}: Finlay MC;Mosse CA;Colchester RJ;Noimark S;Zhang EZ;Ourselin S;Beard PC;Schilling RJ;Parkin IP;Papakonstantinou I;Desjardins AE;
{Journal}: Light Sci Appl
{Volume}: 6
{Issue}: 12
{Year}: Dec 2017
{Factor}: 20.257
{DOI}: 10.1038/lsa.2017.103
{Abstract}: High-frequency ultrasound imaging can provide exquisite visualizations of tissue to guide minimally invasive procedures. Here, we demonstrate that an all-optical ultrasound transducer, through which light guided by optical fibers is used to generate and receive ultrasound, is suitable for real-time invasive medical imaging in vivo. Broad-bandwidth ultrasound generation was achieved through the photoacoustic excitation of a multiwalled carbon nanotube-polydimethylsiloxane composite coating on the distal end of a 300-μm multi-mode optical fiber by a pulsed laser. The interrogation of a high-finesse Fabry-Pérot cavity on a single-mode optical fiber by a wavelength-tunable continuous-wave laser was applied for ultrasound reception. This transducer was integrated within a custom inner transseptal needle (diameter 1.08 mm; length 78 cm) that included a metallic septum to acoustically isolate the two optical fibers. The use of this needle within the beating heart of a pig provided unprecedented real-time views (50 Hz scan rate) of cardiac tissue (depth: 2.5 cm; axial resolution: 64 μm) and revealed the critical anatomical structures required to safely perform a transseptal crossing: the right and left atrial walls, the right atrial appendage, and the limbus fossae ovalis. This new paradigm will allow ultrasound imaging to be integrated into a broad range of minimally invasive devices in different clinical contexts.