Multispectral polarization-resolved endoscopy and vision for intraoperative imaging of tissue microstructure and function

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The paradigm of modern surgical treatment is to reduce the invasive trauma of procedures by using small keyhole ports to enter the body with endoscopic imaging used to see the interior. In clinical endoscopic investigations, information about tissue characteristics or function is therefore limited to colours and features that are visible from white light reflection images, which correspond well to vision by naked eye but only represent a small part of what may be recorded with modern image sensors. Efforts are well underway to bring multispectral (or narrow band imaging), visible and near infrared fluorescence, and microscopic/endoconfocal modalities into endoscopic investigations. One interaction that is frequently overlooked is the scattering of polarized light by biological tissue, which is affected in a complex way by the tissue's scattering and absorption properties.As a simple example of how the polarization-resolved interaction can be used in practice, light that is singly scattered preferentially maintains its polarization over multiply scattered light and this can act as a filter for superficial scattering. The depolarization effect can be used to characterise the scatterer sizes and thus for detection of enlarged nuclei found in precancerous pathologies. More complex analysis requires 16 images to be acquired and processed, allowing detailed analysis of depolarization and retardance in particular leading to the detection of early cancer by revealing tissue structural properties such as birefringence and structural alignment. This project will develop advanced endoscopic imaging approaches that better inform the surgeon about tissue structure and function in real-time during a procedure.Underpinned by polarization properties and effects, we will develop a new endoscopic imaging device that will combine a novel approach to polarization resolved endoscopy (PRE) together with computational tools and models to understand the images it can acquire. This will include Monte Carlo modelling of the polarized light-tissue interaction and approaches for registering, processing and reducing the number of polarized images required for diagnostics. The aim is to produce a clinical instrument that can be applied in the detection and characterisation of peritoneal carcinomatosis, a form of metastatic disease that is common for ovarian and colorectal cancers. This requires image registration, augmentation and data reduction as well as simplified endoscopic hardware. Beyond this immediate clinical investigation, there are a range of screening and image-guided procedures that may be aided by PRE.As well as having direct applications in surgery, the PRE imaging paradigm will be applicable to many other sectors transformed by powerful, small profile imaging endoscopes, for example manufacturing or inspection in constrained environments. For this cross sector impact to be achieved the project will build theoretical knowledge and robust software platforms as well as hardware and optical solutions.