David E. Morris

Short communication: A web-based tool for eliciting probability distributions from experts

We present a web-based probability distribution elicitation tool: The MATCH Uncertainty Elicitation Tool. The Tool is designed to help elicit probability distributions about uncertain model parameters from experts, in situations where suitable data is either unavailable or sparse. The Tool is free to use, and offers five different techniques for eliciting univariate probability distributions. A key feature of the Tool is that users can log in from different sites and view and interact with the same graphical displays, so that expert elicitation sessions can be conducted remotely (in conjunction with tele- or videoconferencing). This will make probability elicitation easier in situations where it is difficult to interview experts in person. Even when conducting elicitation remotely, interviewers will be able to follow good elicitation practice, advise the experts, and provide instantaneous feedback and assistance.

Exploring the Potential for Automatic Extraction of Vegetation Phenological Metrics from Traffic Webcams

Phenological metrics are of potential value as direct indicators of climate change. Usually they are obtained via either satellite imaging or ground based manual measurements; both are bespoke and therefore costly and have problems associated with scale and quality. An increase in the use of camera networks for monitoring infrastructure offers a means of obtaining images for use in phenological studies, where the only necessary outlay would be for data transfer, storage, processing and display. Here a pilot study is described that uses image data from a traffic monitoring network to demonstrate that it is possible to obtain usable information from the data captured. There are several challenges in using this network of cameras for automatic extraction of phenological metrics, not least, the low quality of the images and frequent camera motion. Although questions remain to be answered concerning the optimal employment of these cameras, this work illustrates that, in principle, image data from camera networks such as these could be used as a means of tracking environmental change in a low cost, highly automated and scalable manner that would require little human involvement.

Reduction of error in spectrophotometry of scattering media using polarization techniques.

Scattering can result in erroneous determination of the concentrations of constituent absorbers in spectrophotometry. This is due to the relationship between attenuation and absorption coefficient becoming nonlinear; hence, the use of the Lambert–Beer law becomes invalid. It has previously been shown that application of polarization techniques can reduce these effects, resulting in a more linear relationship. Here we quantify the impact of this improvement on measurement of the ratio of concentrations for two general absorbing species and show that measurement using polarization-maintaining light is more accurate. This is performed using a generalized version of theory previously dependent on selection of isosbestic wavelengths. For the absorbing species and geometries considered here, the mean error on the estimation of absorber concentration ratio is 18.2% for the case of detection without polarization discrimination. When polarization-maintaining light is extracted, mean errors of 1.2% and 5.1% are achieved for linear and circular polarizations, respectively. The improvement provided by the polarization techniques is observed regardless of the illuminating wavelengths but is achieved at the expense of a reduced signal-to-noise ratio. Taking this into account, for the detection scheme considered with a detector well capacity of 4 × 105 electrons the improvement provided by linear polarization-maintaining light is reduced to a factor of 3.6 and for circular polarizations a factor of 2.2.

Thermal imaging is a non-invasive alternative to PET-CT for measurement of brown adipose tissue activity in humans

Obesity and its metabolic consequences are a major cause of morbidity and mortality. Brown adipose tissue (BAT) utilizes glucose and free fatty acids to produce heat, thereby increasing energy expenditure. Effective evaluation of human BAT stimulators is constrained by the current standard method of assessing BAT—PET/CT—as it requires exposure to high doses of ionizing radiation. Infrared thermography (IRT) is a potential noninvasive, safe alternative, although direct corroboration with PET/CT has not been established. Methods: IRT and 18F-FDG PET/CT data from 8 healthy men subjected to water-jacket cooling were directly compared. Thermal images were geometrically transformed to overlay PET/CT-derived maximum intensity projection (MIP) images from each subject, and the areas with the most intense temperature and glucose uptake within the supraclavicular regions were compared. Relationships between supraclavicular temperatures (TSCR) from IRT and the metabolic rate of glucose uptake (MR(gluc)) from PET/CT were determined. Results: Glucose uptake on MR(gluc)MIP was found to correlate positively with a change in TSCR relative to a reference region (r2 = 0.721; P = 0.008). Spatial overlap between areas of maximal MR(gluc)MIP and maximal TSCR was 29.5% ± 5.1%. Prolonged cooling, for 60 min, was associated with a further TSCR rise, compared with cooling for 10 min. Conclusion: The supraclavicular hotspot identified on IRT closely corresponded to the area of maximal uptake on PET/CT-derived MR(gluc)MIP images. Greater increases in relative TSCR were associated with raised glucose uptake. IRT should now be considered a suitable method for measuring BAT activation, especially in populations for whom PET/CT is not feasible, practical, or repeatable.

Quantitative spectrophotometry of scattering media via frequency-domain and constant-intensity measurements

The attenuation of light by scattering and absorbing media is nonlinearly dependent upon the absorption coefficient, since detected light has experienced many different flight times. The frequency response of such a sample to modulated light is also nonlinear. We derive an expression for the attenuation that includes both the absorption coefficient and the modulation frequency. Its form is a power series whose coefficients are the cumulants of the temporal point-spread function (TPSF). Recasting this expression in terms of intensity leads to a similar expression with the cumulants replaced by the moments of the TPSF. A means of exploiting this relationship to produce estimates of the absolute concentration of the absorbing species is suggested.

Time-optimized X-ray micro-CT imaging of polymer based scaffolds†

Although X-ray microscopic computed tomography is widely used to assess the structural properties of polymeric tissue scaffolds its validity is dependent on the quality of the images obtained. Here, the role of resolution, integration time, image averaging, and X-ray power on the accurate determination of scaffold porosity, while aiming to minimize imaging time, was investigated. This work identified key parameters for optimization and a methodology to vary them to improve results. Based on this, guidelines were developed to assist in the selection of image acquisition parameters to allow rapid and accurate scaffold imaging as required for mass manufacture.

The use of infrared thermography in the measurement and characterization of brown adipose tissue activation

ABSTRACT Interest in brown adipose tissue has increased in recent years as a potential target for novel obesity, diabetes and metabolic disease treatments. One of the significant limitations to rapid progress has been the difficulty in measuring brown adipose tissue activity, especially in humans. Infrared thermography (IRT) is being increasingly recognized as a valid and complementary method to standard imaging modalities, such as positron emission tomography–computed tomography (PET/CT). In contrast to PET/CT, it is non-invasive, cheap and quick, allowing, for the first time, the possibility of large studies of brown adipose tissue (BAT) on healthy populations and children. Variations in study protocols and analysis methods currently limit direct comparison between studies but IRT following appropriate BAT stimulation consistently shows a change in supraclavicular skin temperature and a close association with results from BAT measurements from other methods.

Generation and simulated imaging of pseudo-scaffolds to aid characterisation by X-ray micro CT.

In order to assess the suitability of polymer tissue scaffolds for use in regenerative medicine, methods to characterise scaffolds are needed. This requires the scaffolds structure to be determined for which X-ray microscopic computed tomography (X-ray micro CT) is widely used. However, because scaffolds are generally made of materials with low X-ray attenuating properties the images produced are far from ideal, which makes distinguishing scaffold material from the pores within it a non-trivial process. This paper presents a method for generating computer-simulated scaffolds that resemble the form of foamed polymer tissue scaffolds. Virtual images of the scaffold are then produced via a simulated X-ray micro CT process enabling the effect of varying the key parameters in the imaging process to be investigated. Here this is assessed via the calculated porosity of the sample, this being a simple measure of a scaffolds properties. Results highlight the difficulties in using X-ray micro CT to characterise scaffolds constructed from materials with low X-ray attenuating properties and suggest strategies that may be adopted in order to improve the quality of the images produced.

An automated quasi-continuous capillary refill timing device.

Capillary refill time (CRT) is a simple means of cardiovascular assessment which is widely used in clinical care. Currently, CRT is measured through manual assessment of the time taken for skin tone to return to normal colour following blanching of the skin surface. There is evidence to suggest that manually assessed CRT is subject to bias from ambient light conditions, a lack of standardisation of both blanching time and manually applied pressure, subjectiveness of return to normal colour, and variability in the manual assessment of time. We present a novel automated system for CRT measurement, incorporating three components: a non-invasive adhesive sensor incorporating a pneumatic actuator, a diffuse multi-wavelength reflectance measurement device, and a temperature sensor; a battery operated datalogger unit containing a self contained pneumatic supply; and PC based data analysis software for the extraction of refill time, patient skin surface temperature, and sensor signal quality. Through standardisation of the test, it is hoped that some of the shortcomings of manual CRT can be overcome. In addition, an automated system will facilitate easier integration of CRT into electronic record keeping and clinical monitoring or scoring systems, as well as reducing demands on clinicians. Summary analysis of volunteer (n = 30) automated CRT datasets are presented, from 15 healthy adults and 15 healthy children (aged from 5 to 15 years), as their arms were cooled from ambient temperature to 5°C. A more detailed analysis of two typical datasets is also presented, demonstrating that the response of automated CRT to cooling matches that of previously published studies.

Determination of the validity of spectrophotometric measurements based upon cumulants of the temporal point-spread function.

Spectrophotometric measurements of scattering media are nontrivial owing to the nonlinear relationship between the observed attenuation A and the level of absorption coefficient micro(a). Presented is a method, utilizing frequency-domain measurements, capable of determining the validity of a measured change in micro(a) based purely on the characteristics of a baseline temporal point-spread function. The order of cumulant used is shown to provide variation of the sensitivity of the method, and its use is demonstrated through Monte Carlo simulations of transmission measurements taken from a scattering slab.