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

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.

The impact of the proposed research can be widespread and with ample cross disciplinary potential.

Healthcare: The focus for the project is to improve real-time imaging during surgery. This has the potential to reduce surgical complications, patient readmission, disease specific indications such as positive margins and ischaemia damage during vessel clamping, and generally all operative risks while increasing the success of surgery. These objectives, if achieved, will have a significant measureable impact on reducing mortality in patients and increasing the quality of life post-surgery with potential applications in a wide range of clinical indications. Such impact would have obvious societal and economic measures.

Impact on Medical Technology: Facilitating new imaging during surgery has important synergies with surgical instrumentation, especially with emerging robotic systems. Multinational corporations in this space have recently made significant investments and acquisitions (Google, Johnson & Johnson - Ethicon, Medtronic, Stryker, and others) which are likely to result in a surge in surgical robot devices in the next five years. This will be a fertile ground for commercial exploitation of project outputs. The project management group will also help with links to medical device exploitation pathways.

Academic Impact: The intersection between biophotonics and computational imaging will result in publications at high profile meetings as well as in high-impact journals (see Pathways to Impact and Cost of Support). The PRE hardware will be presented at conferences such as OSA Biomed and ECBO, and published in journals such as Journal of Biophotonics, Biomedical Optics Express etc. Computer vision techniques for real-time surgical procedures is a highly active and challenging area that is strongly represented at international conferences such as MICCAI and IPCAI and additional dissemination can also happen at the leading vision meetings like CVPR, ECCV and ICCV for theoretical work. Because the proposed work will result in new devices, mathematical models and biomedical computing, there will be ample opportunities to disseminate results and findings.

Impact on the Wider Research Community: Combination of PRE, modelling approaches and imaging methodologies through i) data fusion, ii) dimensionality reduction, and iii) modelling and inverse problems, are recognised active topics, not only in surgical imaging, but more widely e.g. in remote monitoring, inspection, assembly line characterisation etc. Cross-fertilization between such different application areas is naturally stimulated through this interaction between ICL and UCL. The Alan Turing Institute, in close proximity to UCL, will allow participation in wider programmes of research in large scale data processing exploiting theoretical developments in mathematics, signal processing and machine learning techniques. The work is directly relevant to the CRUK Imperial Cancer Centre, for which Professor Elson is a Co-Investigator. There is further potential to move towards a trial through the support offered by this, and the Experimental Cancer Medicine Centre. This and the EPSRC Networks will allow a rapid and effective mechanism to present project results.

Impact on teaching: By developing software throughout the project within structured frameworks, the project outputs will contribute to toolbox software that will be used within new and established programmes. Both technical investigators are MSc/MRes Programme Directors and can facilitate as well as manage such opportunities.