Ultra-miniature dual-wavelength spatial frequency domain imaging for micro-endoscopy

There is a need for a cost-effective, quantitative imaging tool that can be deployed endoscopically to better detect early stage gastrointestinal cancers. Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that produces near-real time, quantitative maps of absorption and reduced scattering coefficients, but most implementations are bulky and suitable only for use outside the body. We present an ultra-miniature SFDI system comprised of an optical fiber array (diameter 0.125 mm) and a micro camera (1 x 1 mm package) displacing conventionally bulky components, in particular the projector. The prototype has outer diameter 3 mm, but the individual components dimensions could permit future packaging to < 1.5 mm diameter. We develop a phase-tracking algorithm to rapidly extract images with fringe projections at 3 equispaced phase shifts in order to perform SFDI demodulation. To validate performance, we first demonstrate comparable recovery of quantitative optical properties between our ultra-miniature system and a conventional bench-top SFDI system with agreement of 15% and 6% for absorption and reduced scattering respectively. Next, we demonstrate imaging of absorption and reduced scattering of tissue-mimicking phantoms providing enhanced contrast between simulated tissue types (healthy and tumour), done simultaneously at wavelengths of 515 nm and 660 nm. This device shows promise as a cost-effective, quantitative imaging tool to detect variations in optical absorption and scattering as indicators of cancer.Comment: 26 Pages, 7 Figure

Ultra-miniaturised spatial frequency domain imaging for improved early detection of gastrointestinal cancers

The low five year-survival rates for gastrointestinal cancers evidences a strong clinical need to improve their early detection. Current imaging methods for early detection are expensive and rely on white light imaging which lacks sufficient contrast to spot a wide range of potential tumours. Changes in absorption and reduced scattering coefficients can be linked to pre-cancerous abnormalities, such as Barrett’s Oesophagus, and invasive squamous cell carcinoma, in the oesophagus. Spatial Frequency Domain Imaging (SFDI) is a low-cost imaging technique from which quantitative maps of absorption and reduced scattering coefficients may be obtained using structured illumination. We have developed a clinically translatable, ultra-miniaturised SFDI system using optical fibers (0.125 mm diameter) to project structured illumination and a miniature camera (< 1 mm diameter) to capture the pattern response for a sample under test. The total package could therefore be made < 1.1mm diameter, representing, to the best of our knowledge, the smallest full SFDI probe achieved to date. We have demonstrated recovery of absorption and reduced scattering maps with our system for tissue mimicking co-polymer in oil phantoms of biologically relevant absorption and scattering properties. This technology represents a first step towards a less-invasive, cost-effective device which produces close to real-time absorption and reduced scattering maps for improved in vivo disease detection of the gastrointestinal tract

Inkjet printed LED based pH chemical sensor for gas sensing

Predictable behaviour is a critical factor when developing a sensor for potential deployment within a wireless sensor network (WSN). The work presented here details the fabrication and performance of an optical chemical sensor for gaseous acetic acid analysis, which was constructed using inkjet printed deposition of a colorimetric chemical sensor. The chemical sensor comprised a pH indicator dye (bromophenol blue), phase transfer salt tetrahexylammonium bromide and polymer ethyl cellulose dissolved in 1-butanol. A paired emitter-detector diode (PEDD) optical detector was employed to monitor responses of the colorimetric chemical sensor as it exhibits good sensitivity, low power consumption, is low cost, accurate and has excellent signal to noise ratios. The chemical sensor formulation was printed directly onto the surface the emitter LED, and the resulting chemical sensors characterised with respect to their layer thickness, response time and recovery time. The fabrication reproducibility of inkjet printed chemical sensors in comparison to drop casted chemical sensors was investigated. Colorimetric chemical sensors produced by inkjet printing, exhibited an improved reproducibility for the detection of gaseous acetic acid with a relative standard deviation of 5.5 % in comparison to 68.0 % calculated for drop casted sensors (n = 10). The stability of the chemical sensor was also investigated through both intra and inter-day studies

Simulating medical applications of tissue optical property and shape imaging using open-source ray tracing software

Oesophageal cancer and colon cancer have five year survival rates of 15% and 63% respectively. These low survival rates are due in part to poor early detection during endoscopic screening, with conventional endoscopes providing insufficient information about tissue properties to spot a wide range of potential tumours. Improving early detection of gastrointestinal cancers would dramatically increase their five year survival rates. Spatial Frequency Domain Imaging (SFDI) is a low-cost imaging technique that can measure absorption, scattering and shape as potential indicators of cancer. Specific absorption and scattering properties are known to be linked to malignancy in the oesophagus, and shape is an important indicator in colon cancer. Though a range of research and commercial SFDI systems have been developed, adapting these for in vivo clinical application is challenging due to constraints imposed by miniaturisation, sample geometry and illumination conditions. To facilitate design of novel SFDI systems under such constraints, we have developed a model of an SFDI imaging system built on the open-source 3D modelling software Blender. Using Blender’s Cycles ray-tracing engine, we are able to simulate a range of different scattering and absorption coefficients for a number of different imaging configurations, sample geometries and illumination patterns. Using established processing algorithms, we show we can recover maps of absorption, scattering and shape in a range of simulated ex vivo and in vivo imaging geometries with relevance to clinical detection of tumours. Our system enables accessible exploration of different optical configurations and realistic illumination conditions that will inform future design of compact, low-cost instruments

Beyond the Comfort Zone: A Guide to Supervising Qualitative Undergraduate Psychology Dissertations for Quantitative Researchers

The Teaching Qualitative Psychology Group (TQP) is a group of experienced academics supporting the sharing of best practice in the teaching and supervision of qualitative research methods in psychology. In this paper the group share their knowledge and practice suggestions with a specific focus on supporting academics who do not come from a qualitative research background, but who are supervising qualitative dissertations. This paper will explore why quantitative researchers may want to supervise qualitative dissertations and suggest ways in which this methodological shift might be managed well in the context of the undergraduate project as well as some practical advice for a valuable supervision experience

Sentry bioconvertible inferior vena cava filter: Study of stages of incorporation in an experimental ovine model

The Sentry inferior vena cava (IVC) filter is designed to provide temporary protection from pulmonary embolism (PE) and then bioconvert to become incorporated in the vessel wall, leaving a patent IVC lumen. Objective. To evaluate the performance and stages of incorporation of the Sentry IVC filter in an ovine model. Methods. Twenty-four bioconvertible devices and 1 control retrievable filter were implanted in the infrarenal IVC of 25 sheep, with extensive daily monitoring and intensive imaging. Vessels and devices were analyzed at early (≤98 days, n = 10) and late (180 ± 30 days, n = 14 study devices, 1 control) termination and necropsy time-points. Results. Deployment success was 100% with all devices confirmed in filtering configuration, there were no filter-related complications, and bioconversion was 100% at termination with vessels widely patent. By 98 days for all early-incorporation analysis animals, the stabilizing cylindrical part of the Sentry frame was incorporated in the vessel wall, and the filter arms were retracted. By 180 days for all late-incorporation analysis animals, the filter arms as well as frames were stably incorporated. Conclusions. Through 180 days, there were no filter-related complications, and the study devices were all bioconverted and stably incorporated, leaving all IVCs patent

Bronchoscopy masks mitigate aerosols during upper gastrointestinal endoscopies

Background and study aims: Upper gastrointestinal endoscopies are considered aerosol-generating procedures (AGP) that risk spread of airborne diseases such as SARS-CoV-2. We aimed to investigate where clinically approved bronchoscopy masks applied to patients during esophagogastroduodenoscopies can mitigate spread of aerosols and droplets.Patients and methods: This study included patients undergoing routine upper gastrointestinal endoscopy in a standard endoscopy room and used a particle counter to measure size and number of particles 10 cm from the mouths of 49 patients undergoing upper gastrointestinal endoscopies, of whom 12 wore bronchoscopy masks and 37 did not (controls). Particle counts in the aerosol (≤ 5 µm diameter) and droplet (> 5 µm-diameter) size ranges were measured and averaged over the duration of procedures.Results: The use of bronchoscopy masks offers a 47% reduction (P = 0.01) in particle count for particles < 5 μm in diameter over the procedure duration (aerosols).Conclusions: Bronchoscopy masks or similar are a simple, low-cost mitigation technique that can be used during outbreaks of respiratory diseases such as COVID-19 to improve safety and reduce fallow times

Factors determining social participation in the first year after kidney transplantation: a prospective study

BACKGROUND: This study describes changes in social participation in the first year after kidney transplantation and examines the influence of clinical factors, health status, transplantation-related symptoms, and psychological characteristics on change in social participation. METHODS: A prospective study was performed on a cohort of primary kidney transplant recipients, transplanted between March 2002 and March 2003. Data on participation in obligatory activities (i.e., employment, education, household tasks) and leisure activities (i.e., volunteer work, assisting others, sports, clubs/associations, recreation, socializing, going out) were collected by in-home interviews (n=61) at 3 months (T1) and 1 year posttransplantation (T2). Analysis of covariance was performed. RESULTS: Data showed an increase in participation in obligatory activities and diversity of leisure participation between T1 and T2, although pre-end-stage renal disease level was not regained and differed from the general population. On T1, the majority of employed recipients were on sick leave, but returned to work on T2. Employment rate remained stable. An increase in obligatory participation was predicted by clinical factors (i.e., peritoneal dialysis, initial hospitalization), whereas change in leisure participation was related to serum albumin and cognitive capacity. No effects were found for type of donation, comorbidity, and renal function. CONCLUSIONS: We found that mainly clinical factors were associated with an increase in participation in society. Although health-status related factors and the psychological attribute self-efficacy may be related to recovery of social participation, their effect was outweighed by the strength of clinical predictors in multivariate analysis