Coherent Multi-Transducer Ultrasound Imaging

An extended aperture has the potential to greatly improve ultrasound imaging performance. This work extends the effective aperture size by coherently compounding the received radio frequency data from multiple transducers. A framework is developed in which an ultrasound imaging system consisting of $N$ synchronized matrix arrays, each with partly shared field of view, take turns to transmit plane waves. Only one individual transducer transmits at each time while all $N$ transducers simultaneously receive. The subwavelength localization accuracy required to combine information from multiple transducers is achieved without the use of any external tracking device. The method developed in this study is based on the study of the backscattered echoes received by the same transducer and resulting from a targeted scatterer point in the medium insonated by the multiple ultrasound probes of the system. The current transducer locations along with the speed of sound in the medium are deduced by optimizing the cross-correlation between these echoes. The method is demonstrated experimentally in 2-D using ultrasound point and anechoic lesion phantoms and a first demonstration of a free-hand experiment is also shown. Results demonstrate that the coherent multi-transducer imaging has the potential to improve ultrasound image quality, improving resolution and target detectability. Lateral resolution, contrast and contrast-to-noise ratio improved from 0.67 mm, -6.708 dB and 0.702, respectively, when using a single probe, to 0.18 mm, -7.251 dB and 0.721 in the coherent multi-transducer imaging case

ESA Nanosatellites for D3S (Distributed Space Weather Sensor System)

In early 2021, SSTL was selected to be the prime contractor for an ongoing 18 month ESA-funded Phase 0/A study titled “SSA P3-SWE-LIII Nanosatellites for D3S”. The objective of the study is to assess the feasibility of using nanosatellites for future operational space weather monitoring missions as part of ESA's Distributed Space Weather Sensor System (D3S). The Phase 0 study initially involved an analysis of science measurement requirements and space weather instruments as well as an analysis of recent relevant nanosatellite missions and nanosatellite technologies which could be used on future ESA D3S Nanosatellites. This was followed by an initial trade-off of a range of high-level mission architecture concepts, eventually converging down to two mission architecture concepts proposed for further analysis during the remainder of the Phase 0 study. The aim of the first mission architecture concept is to provide near-real time measurements of radiation, thermal plasma and Ionospheric neutrals/plasma, via a constellation of 20x SSTL-21 satellites. The objective of the second mission architecture concept is to provide near-real time measurements of radiation, the Ionosphere and the Thermosphere, via a constellation of 6x 16U SSTL-Cube satellites. ESA selected the second mission architecture concept to take through into the Phase A study. This paper will mainly describe the details of the Phase 0 study, as well as touching on the current status of the Phase A study

Clogging the machinery: the BBC's experiment in science coordination, 1949–1953

In 1949, physicist Mark Oliphant criticised the BBC’s handling of science in a letter to the Director General William Haley. It initiated a chain of events which led to the experimental appointment of a science adviser, Henry Dale, to improve the ‘coordination’ of science broadcasts. The experiment failed, but the episode revealed conflicting views of the BBC’s responsibility towards science held by scientists and BBC staff. For the scientists, science had a special status, both as knowledge and as an activity, which in their view obligated the BBC to make special arrangements for it. BBC staff, however, had their own professional procedures which they were unwilling to abandon. The events unfolded within a few years of the end of the Second World War, when social attitudes to science had been coloured by the recent conflict, and when the BBC itself was under scrutiny from the William Beveridge’s Committee. The BBC was also embarking on new initiatives, notably the revival of adult education. These contextual factors bear on the story, which is about the relationship between a public service broadcaster and the external constituencies it relies on, but must appear to remain independent from. The article therefore extends earlier studies showing how external bodies have attempted to manipulate the inner workings of the BBC to their own advantage (e.g. those by Doctor and Karpf) by looking at the little-researched area of science broadcasting. The article is largely based on unpublished archive documents

High-Frame-Rate Contrast Echocardiography using diverging waves: initial in-vitro and in-vivo evaluation

Contrast Echocardiography (CE) ultrasound with microbubble contrast agents (UCA) has significantly advanced our capability for assessment of cardiac function, including myocardium perfusion quantification. However in standard CE techniques obtained with line by line scanning, the frame rate and image quality are limited. Recent research has shown significant frame rate improvement in non-contrast cardiac imaging. In this work we present and initially evaluate, both in-vitro and in-vivo, a high frame rate (HFR) CE imaging system using diverging waves and pulse inversion sequence. An imaging frame rate of 5500 frames per second before and 250 frames per second after compounding is achieved. A destruction-replenishment sequence has also been developed. The developed HFR CE is compared with standard CE in-vitro on a phantom and then in-vivo on a sheep heart. The image signal to noise ratio, contrast between the myocardium and the chamber are evaluated. Results show up to 13.4 dB improvement in contrast for HFR CE over standard CE when compared at the same display frame-rate even when the average spatial acoustic pressure in HFR CE is 36% lower than the standard CE. It is also found that when coherent compounding is used the HFR CE image intensity can be significantly modulated by the flow motion in the chamber