Enhancing photoacoustic visualization of medical devices with elastomeric nanocomposite coatings

Abstract

Ultrasound (US) imaging is widely used for guiding minimally invasive procedures. However, with this modality, there can be poor visibility of interventional medical devices such as catheters and needles due to back-reflections outside the imaging aperture and low echogenicity. Photoacoustic (PA) imaging has shown promise with visualising bare metallic needles. In this study, we demonstrate the feasibility of a light emitting diode (LED)-based PA and US dual-modality imaging system for imaging metallic needles and polymeric medical catheters in biological tissue. Four medical devices were imaged with the system: two 20-gauge spinal needles with and without a multi-walled carbon nanotube / polydimethylsiloxane (MWCNT/PDMS) composite coating, and two 18-gauge epidural catheters with and without the MWCNT/PDMS composite coating. These devices were sequentially inserted into layers of chicken breast tissue within the US imaging plane. Interleaved PA and US imaging was performed during insertions of the needle and catheter. With US imaging, the uncoated needle had very poor visibility at an insertion angle of 45°. With PA imaging, the uncoated needle was not visible, but its coated counterpart was clearly visualised up to depths of 35 mm. Likewise, both catheters were not visible with US imaging. The uncoated catheter was not visible on PA images, but its coated counterpart was clearly visualised up to depths of 35 mm. We conclude that the highly absorbing CNT/PDMS composite coating conferred excellent visibility for medical devices with the LED-based PA imaging system and that it is promising for translation in minimally invasive procedures.