Fabrication of an Array of Eccentric Sources for Freehand Optical Ultrasound Imaging

Free-hand optical ultrasound (OpUS) imaging is an emerging ultrasound imaging paradigm that utilises an array of fiber-optic sources and a fiber-optic detector to achieve video-rate, real-time imaging, with a flexible probe. Previous designs used multimode fibers to achieve circular OpUS sources that emitted divergent fields propagating away from the imaging plane, resulting in image artefacts and reduced penetration depths. The directivity of the emitted ultrasound field can be optimised by changing the trasnducer shape, moving to eccentric transducers can improve elevational confinement and associated aretefacts. In this work, methods for fabricating suitably eccentric waveguides that can be placed distally to a fiber-bundle array probe are presented. In addition, the scalability of one of these methods is demonstrated by fabricating a ten-element array of waveguides.