Mapping cortical haemodynamics during neonatal seizures using diffuse optical tomography: A case study

AbstractSeizures in the newborn brain represent a major challenge to neonatal medicine. Neonatal seizures are poorly classified, under-diagnosed, difficult to treat and are associated with poor neurodevelopmental outcome. Video-EEG is the current gold-standard approach for seizure detection and monitoring. Interpreting neonatal EEG requires expertise and the impact of seizures on the developing brain remains poorly understood. In this case study we present the first ever images of the haemodynamic impact of seizures on the human infant brain, obtained using simultaneous diffuse optical tomography (DOT) and video-EEG with whole-scalp coverage. Seven discrete periods of ictal electrographic activity were observed during a 60 minute recording of an infant with hypoxic–ischaemic encephalopathy. The resulting DOT images show a remarkably consistent, high-amplitude, biphasic pattern of changes in cortical blood volume and oxygenation in response to each electrographic event. While there is spatial variation across the cortex, the dominant haemodynamic response to seizure activity consists of an initial increase in cortical blood volume prior to a large and extended decrease typically lasting several minutes. This case study demonstrates the wealth of physiologically and clinically relevant information that DOT–EEG techniques can yield. The consistency and scale of the haemodynamic responses observed here also suggest that DOT–EEG has the potential to provide improved detection of neonatal seizures

A novel treatment for pathogen reduction

The body routinely encounters new micro-organisms and epithelial surfaces provide the first line of defence. Most micro-organisms that get passed this barrier are detected and eliminated by the immune system. The liver plays an important role. Patients suffering from acute liver failure (ALF) are more prone to bacterial infections, and death from sepsis is not uncommon. Liver transplantation, is a successful therapy available for ALF, but too few donor organs are available. A bio-artificial liver (BAL) machine could “buy time” for a patient to recover or to bridge to eventual transplantation. An extracorporeal device was developed that can be integrated into the BAL, to treat in real time plasma infections, eliminating pathogens whilst conserving the integrity and functionality of plasma components, as one component of the BAL. Our hypothesis was that phototreatment is the most suitable pathogen reduction technology (PRT) for real time applications. The efficacy of a number of photosensitisers and light sources were evaluated. Custom equipment was developed to investigate the characteristics of semiconductor light sources. Their optimum operating conditions were investigated in terms of operating temperature, supply current and placement. Further experiments were performed to select appropriate materials for the construction of the phototreatment exposure unit. A first PRT prototype was developed and used to illuminate samples of E. coli in saline solution. The experiments demonstrated more than 4 log 10 reduction of surviving colony formation units, thus proving the method antimicrobial. A second PRT prototype was developed and used with a wider choice of light intensity, wavelengths and photosensitisers. It was used to perform further phototreatment experiments against E. coli, S. warneri and C. albicans. Significant reduction of pathogens was demonstrated in all cases. This thesis has demonstrated the initial proof of this hypothesis, leading to further in- vestigations being performed and the development of a clinical scale model

Shared memories: a trail-based coordination server for robot teams

Robust, dependable and concise coordination between members of a robot team is a critical ingredient of any such collective activity. Depending on the availability and the characteristics of the particular communication infrastructure, coordination mechanisms can take varied forms, leading to distinct system behaviors. In this paper, we consider the case of robot teams operating within relatively sparse wireless sensor network deployments. We introduce Shared Memories, a trail-based coordination engine, that analyzes interaction patterns between participating team members and sensor network nodes capable to discover significant aggregate patterns, which are made available to the team. To this end, we propose a model for the representation of captured interactions and their sensory context developed as a probabilistic grammar, as well as associated metrics used to rank trails and quantify their significance. Such trails are used as the basis for coordinated operation in team tasks and are made available by the engine to all team members. Our implementation deploys ad-hoc wireless local networking capability available through surrogate devices to commodity robots and RFID proximity sensors. We report on the performance of this system in experiments conducted in a laboratory environment, which highlight the advantages and limitations of our approach

Towards a wearable near infrared spectroscopic probe for monitoring concentrations of multiple chromophores in biological tissue in vivo

The first wearable multi-wavelength technology for functional near-infrared spectroscopy has been developed, based on a custom-built 8-wavelength light emitting diode (LED) source. A lightweight fibreless probe is designed to monitor changes in the concentrations of multiple absorbers (chromophores) in biological tissue, the most dominant of which at near-infrared wavelengths are oxyhemoglobin and deoxyhemoglobin. The use of multiple wavelengths enables signals due to the less dominant chromophores to be more easily distinguished from those due to hemoglobin and thus provides more complete and accurate information about tissue oxygenation, hemodynamics, and metabolism. The spectroscopic probe employs four photodiode detectors coupled to a four-channel charge-to-digital converter which includes a charge integration amplifier and an analogue-to-digital converter (ADC). Use of two parallel charge integrators per detector enables one to accumulate charge while the other is being read out by the ADC, thus facilitating continuous operation without dead time. The detector system has a dynamic range of about 80 dB. The customized source consists of eight LED dies attached to a 2 mm × 2 mm substrate and encapsulated in UV-cured epoxy resin. Switching between dies is performed every 20 ms, synchronized to the detector integration period to within 100 ns. The spectroscopic probe has been designed to be fully compatible with simultaneous electroencephalography measurements. Results are presented from measurements on a phantom and a functional brain activation study on an adult volunteer, and the performance of the spectroscopic probe is shown to be very similar to that of a benchtop broadband spectroscopy system. The multi-wavelength capabilities and portability of this spectroscopic probe will create significant opportunities for in vivo studies in a range of clinical and life science applications