Overcoming tissue specular reflection challenges in micro camera endoscopy for in-vivo clinical applications.

Abstract

Surgical guidance and diagnostics by diffuse optical imaging using micro camera technology at the tip endoscopic probes have the potential to act as intra-operative supportive tools for clinicians. Micro camera probes need to address undesirable specular reflections in order to be clinically relevant. In this work we overcome specular reflections caused by the glossy uneven tissue surface. We adapt and compare two techniques for miniaturised probes designed to view tissue. Two camera probes are developed using different modalities to remove these surface reflections, with line-of-sight to further miniaturisation. 1) The multi-flash technique illuminates the sample from four different positions, causing a shift in reflections which is filtered out in a post processing image reconstruction step. 2) The cross polarisation technique integrates orthogonal polarisers on to the tip of the illumination fibres and camera, respectively, to filter out the polarisation maintaining reflections. These form part of an imaging system that is capable of rapid image acquisition using different illumination wavelengths. The system is validated on tissue mimicking phantoms with high surface reflection, as well as excised human breast tissue. It is demonstrated that both methods effectively remove the specular reflections, revealing previously hidden underlying information. The methods demonstrate two effective options for improving image quality in miniaturised systems, for human and machine observers, in a surgical setting.