Speckle interferometry using a hardwired autocorrelator

Imperial Users onl

Exploring the feasibility of wavelength modulated near-infrared spectroscopy

Significance: The application of near-infrared spectroscopy (NIRS) to determine the concentrations of tissue chromophores has typically relied on three alternative technological approaches: continuous-wave, frequency-domain, and time-domain. It is often the case that uncertain and variable coupling of light into and out of the skin surface renders absolute measurements unreliable, and NIRS methods are mostly used to measure changes of chromophore concentrations and of physiological parameters such as blood volume and oxygenation. Aim: The aim has been to investigate whether an approach based on a wavelength-modulated source may enable measurements to be acquired, which are independent of surface coupling and may facilitate derivation of absolute values of tissue parameters. Approach: An analysis is performed using the modified Beer–Lambert law. Results: It is shown that the relative modulation in detected intensity resulting from a wavelength-modulated source could be used to estimate absolute concentrations of chromophores if unknown surface coupling losses and geometrical factors are insensitive to small changes in wavelength. Conclusions: Wavelength modulated NIRS could be an effective tool for quantitative in vivo analysis of tissues, although it may be technically challenging

Ultrasound scanner—Teaching tool

Ultrasound imaging, one of the most widely used diagnostic modalities, anchors the fields of medicine, physics, and engineering. In university classrooms, however, ultrasound imaging is often taught passively with a lack of practical element as the clinical machines are not easily available and there are very few alternative teaching tools available on the market. As part of an undergraduate student project, we have developed a teaching toolkit featuring an inexpensive ultrasonic range finder to demonstrate the pulse-echo imaging process. The primary focus is the construction of equipment to enable known pedagogic principles (relating to active learning) to be applied to the subject area of ultrasound. Although operating at an acoustic frequency considerably lower than that employed clinically (and therefore achieving a much lower spatial resolution), the toolkit provides students with large observable effects while keeping cost to the minimum. Completed with an easy-to-use user interface and a set of carefully designed supplementary material (https://stacks.iop.org/EJP/42/055703/mmedia) including worksheets and lab technician guide, this toolkit aims to teach students the fundamental principles of ultrasound imaging via hands-on practice. We have designed it to be cheap, easy to set up, and portable. The effectiveness and impact of the toolkit were evaluated by ten undergraduate students who responded in the form of satisfaction questionnaires. To minimise the selection bias, we chose five students who had received no prior university-based instruction on ultrasound and five third-year biomedical engineering students who had learned about the topic previously. They demonstrated a strong interest in using the toolkit for a lab session and described it as user-friendly and highly engaging

Quality assurance in proton beam therapy using a plastic scintillator and a commercially available digital camera

PURPOSE: In this article, we evaluate a plastic scintillation detector system for quality assurance in proton therapy using a BC-408 plastic scintillator, a commercial camera, and a computer. METHODS: The basic characteristics of the system were assessed in a series of proton irradiations. The reproducibility and response to changes of dose, dose-rate, and proton energy were determined. Photographs of the scintillation light distributions were acquired, and compared with Geant4 Monte Carlo simulations and with depth-dose curves measured with an ionization chamber. A quenching effect was observed at the Bragg peak of the 60 MeV proton beam where less light was produced than expected. We developed an approach using Birks equation to correct for this quenching. We simulated the linear energy transfer (LET) as a function of depth in Geant4 and found Birks constant by comparing the calculated LET and measured scintillation light distribution. We then used the derived value of Birks constant to correct the measured scintillation light distribution for quenching using Geant4. RESULTS: The corrected light output from the scintillator increased linearly with dose. The system is stable and offers short-term reproducibility to within 0.80%. No dose rate dependency was observed in this work. CONCLUSIONS: This approach offers an effective way to correct for quenching, and could provide a method for rapid, convenient, routine quality assurance for clinical proton beams. Furthermore, the system has the advantage of providing 2D visualization of individual radiation fields, with potential application for quality assurance of complex, time-varying fields

Building local capacity in the arts

© 2016 Informa UK Limited, trading as Taylor & Francis GroupThe importance of place-based funding and local policy initiatives is evident in policy literature internationally with concepts of creative cities and cultural regeneration building in prominence since the 1990s. Such literature makes the case that investment in arts and culture will bring broader social and economic benefits at a local level, but in practice investment and research has prioritised a small number of metropolitan arts venues and mega events over a larger rural or community-based infrastructure. This paper in contrast explores two case studies of cultural planning in small towns. It analyses the relationship between policy and practice in these specific community contexts and considers the role of participatory decision-making in developing a local arts infrastructure. The findings suggest that locally based initiatives can build capacity and engagement with the arts. But it further argues that this requires long-term commitment and investment, to facilitate shared decision-making between professionals and public

Multispectral imaging of the ocular fundus using light emitting diode illumination

We present an imaging system based on light emitting diode (LED) illumination that produces multispectral optical images of the human ocular fundus. It uses a conventional fundus camera equipped with a high power LED light source and a highly sensitive electron-multiplying charge coupled device camera. It is able to take pictures at a series of wavelengths in rapid succession at short exposure times, thereby eliminating the image shift introduced by natural eye movements (saccades). In contrast with snapshot systems the images retain full spatial resolution. The system is not suitable for applications where the full spectral resolution is required as it uses discrete wavebands for illumination. This is not a problem in retinal imaging where the use of selected wavelengths is common. The modular nature of the light source allows new wavelengths to be introduced easily and at low cost. The use of wavelength-specific LEDs as a source is preferable to white light illumination and subsequent filtering of the remitted light as it minimizes the total light exposure of the subject. The system is controlled via a graphical user interface that enables flexible control of intensity, duration, and sequencing of sources in synchrony with the camera. Our initial experiments indicate that the system can acquire multispectral image sequences of the human retina at exposure times of 0.05 s in the range of 500-620 nm with mean signal to noise ratio of 17 dB (min 11, std 4.5), making it suitable for quantitative analysis with application to the diagnosis and screening of eye diseases such as diabetic retinopathy and age-related macular degeneration

Monitoring the response to neoadjuvant hormone therapy for locally advanced breast cancer using three-dimensional time-resolved optical mammography.

Optical mammography is a functional imaging technique that uses near-infrared light to produce three-dimensional breast images of tissue oxygen saturation and hemoglobin concentration. It has been used to monitor the response to neoadjuvant chemotherapy in breast cancer patients. We present the first results on monitoring tumor response to hormone therapy using optical mammography. We present three case studies from postmenopausal women treated with neoadjuvant hormone therapy for locally advanced breast cancer. The women were scanned before starting treatment, once during treatment, and then before surgery. Changes in physiological and optical properties within the tumor and in the rest of the breast were evaluated. At the time of surgery, two patients partially responded to treatment and one did not respond. The patients that partially responded on ultrasound revealed a corresponding recovery to normal in the hemoglobin concentration images, whereas the nonresponder indicated an increase in hemoglobin concentration in the tumor compared to her pretreatment images. These case studies suggest that optical imaging of the breast during neoadjuvant hormone treatment can provide potentially valuable information, and that physiological changes within the tumor can be seen in response to treatment

Research volunteers workshop: report on workshop proceedings: discussion, conclusions and next steps

The Research Volunteers Workshop provided the opportunity for a diverse group of stakeholders in biomedical research to come together and discuss the role of the research participants (or ‘subjects’) in contemporary research practice. Those invited included researchers, patients, patient groups, funders, managers and policymakers. The objective was to try and assess practices in order to improve both the experience of the participants, and the quality of research findings. Wellmanaged volunteer involvement has the potential to generate research results that are better honed to public needs, and of more reliable quality. The findings of the workshop have wideranging implications for policy

A dual-wavelength spread spectrum-based spectroscopic system For time-domain near-infrared diffuse optical imaging

We advance our previous research on spread spectrum spectroscopy by adding spectroscopic functionality using a custom-made optical transceiver. The new transceiver module features a 680nm communications-grade verticalcavity surface-emitting laser (VCSEL) and matches the performance of commercial 10Gb/s optical transceivers, which allow for a sub-ns instrument response. The optical power of the VCSEL can be software-adjusted up to 2mW with ∼40μA driving current resolution. This module, combined with a commercially available Gigabit optical transceiver at 850nm, allows us to derive information about the optical properties of tissue-equivalent phantoms and the concentration of various haemodynamic parameters in in vivo measurements

Image reconstruction of oxidized cerebral cytochrome C oxidase changes from broadband near-infrared spectroscopy data

In diffuse optical tomography (DOT), overlapping and multidistance measurements are required to reconstruct depth-resolved images of oxy- ([Formula: see text]) and deoxy- (HHb) hemoglobin concentration changes occurring in the brain. These can be considered an indirect measure of brain activity, under the assumption of intact neurovascular coupling. Broadband systems also allow changes in the redox state of cytochrome c oxidase (oxCCO) to be measured, which can be an important biomarker when neurovascular coupling is impaired. We used DOT to reconstruct images of [Formula: see text], [Formula: see text], and [Formula: see text] from data acquired with a broadband system. Four healthy volunteers were measured while performing a visual stimulation task (4-Hz inverting checkerboard). The broadband system was configured to allow multidistance and overlapping measurements of the participants' visual cortex with 32 channels. A multispectral approach was employed to reconstruct changes in concentration of the three chromophores during the visual stimulation. A clear and focused activation was reconstructed in the left occipital cortex of all participants. The difference between the residuals of the three-chromophore model and of the two-chromophore model (recovering only [Formula: see text] and [Formula: see text]) exhibits a spectrum similar to that of oxCCO. These results form a basis for further studies aimed to further optimize image reconstruction of [Formula: see text]