Logan Williams

Real time multicomponent echo particle image velocimetry technique for opaque flow imaging

This letter reports on a contrast-based ultrasonic particle imaging technique (echo PIV) for measuring multicomponent velocity vectors in opaque flows with excellent temporal (up to 0.5ms) and spatial (up to 0.4mm) resolution. Ultrasound contrast microbubbles are used as flow tracers, and digitally acquired rf data are converted into B-mode images for PIV analysis. Here, velocity fields from various flow patterns (including rotating and transient vortex flows) that are difficult to measure using other opaque flow methods such as ultrasound Doppler or magnetic resonance imaging are measured using echo PIV. This nonintrusive technique should be a promising addition to opaque flow diagnostics.

Development of a custom-designed echo particle image velocimetry system for multi-component hemodynamic measurements: system characterization and initial experimental results

We have recently developed an ultrasound-based velocimetry technique, termed echo particle image velocimetry (Echo PIV), to measure multi-component velocity vectors and local shear rates in arteries and opaque fluid flows by identifying and tracking flow tracers (ultrasound contrast microbubbles) within these flow fields. The original system was implemented on images obtained from a commercial echocardiography scanner. Although promising, this system was limited in spatial resolution and measurable velocity range. In this work, we propose standard rules for characterizing Echo PIV performance and report on a custom-designed Echo PIV system with increased spatial resolution and measurable velocity range. Then we employed this system for initial measurements on tube flows, rotating flows and in vitro carotid artery and abdominal aortic aneurysm (AAA) models to acquire the local velocity and shear rate distributions in these flow fields. The experimental results verified the accuracy of this technique and indicated the promise of the custom Echo PIV system in capturing complex flow fields non-invasively.

Getting Undone Technology Done: Global Techno-assemblage and the Value Chain of Invention:

The global techno-assemblage shapes the continued lagging of southern countries and firms behind those from the global north. The biotechnology industry is one form of this assemblage and operates according to inter-related logics (i.e., economic, hybrid and social) which are shaped by particular governmental policies and corporate decisions to minimise risk and philanthropic efforts. Within this form, a non-profit ophthalmic consumables manufacturing company, Aurolab, in southern India creates new innovations. According to the ‘technology follower’ conceptual framework by innovation studies and management scholars, biotechnology firms have two options to ‘move up’ the international value chain of invention: they must either ‘catch up’ at a very high rate, or ‘leap-frog’ up through research, design and development. Aurolab innovates to heal eye diseases. They focus on affordability issues through research and development as well as design and development. At Aurolab, they shift between these two strategies depending upon the drug or device they are working on. This article considers additional incentives to refocus firms on local needs-based technology according to a social logic. As Aurolab demonstrates, a new focus on technology to address structural inequality may be necessary to get ‘undone technology’ done.

Three Models of Development: Community Ophthalmology NGOs and the Appropriate Technology Movement

Abstract This paper describes a new shift in the appropriate technology movement in less economically developed countries as seen in a multi-sited ethnography of non-governmental organizations (NGOs) in the scientific field of ophthalmology. This research reveals how Aravind Eye Care System in southern India and Tilganga Institute of Ophthalmology in Nepal are addressing “undone science” for avoidable blindness. They are creating the requisite local hospital and personnel infrastructure while conducting “civil society research.” They are also providing high quality modern care to low-income patients of the global south while charging reduced or no fees. This paper argues that they represent a third model in the appropriate technology movement—contextually appropriate local production of high technology. This third model focuses on socially responsible innovation for purposes of social improvement; it is rooted in nonprofit, social enterprise organizations to include the following four aspects: (1) scientific innovation or the “appropriation” of new science; (2) organizational innovation, including changes in operations management for self-sufficiency through multiple revenue streams; (3) technological innovation or the creation of new products and artifacts; and (4) an underlying ideological orientation that is based on local philosophy (and challenges hegemonic understandings of postcolonial dependency or neoliberalism).

Mapping Superpositionality in Global Ethnography

Science studies scholars often study up to high-tech elites who produce and design scientific knowledge and technology. Methodological tension begins when you pair a desire to study down to less economically developed countries, with the desire to study up to high-tech elites within them. This becomes further complicated when the ethnographer and his/her informants share professional interests and credentials. In these situations, the researcher has high status because of geopolitical privilege. However, the researcher is neither a high-tech elite nor a local cultural elite. How might the ethnographer successfully access and navigate field sites imbued with these unseen power differentials? There are currently no visual mapping tools to enhance the process of reflexivity by feminist ethnographers, as they consider their globally embedded multiple, hierarchical, and situated positionality. This reflection methodology piece provides a tool to consider this phenomenon, as it exists across the Global North/South divide of power. Such a tool would be useful to northern ethnographers to better strategize ethics and access while avoiding complicity with structures of inequality and empowering their southern interlocutors.

P2A-5 Effect of Contrast Microbubble Concentration on Quality of Echo Particle Image Velocimetry (Echo PIV) Data: Initial In Vitro Studies

We have recently developed a novel contrast-based ultrasonic particle image velocimetry (Echo PIV) technique to measure multi-component velocity vectors in opaque flows. In the technique, ultrasound contrast microbubbles are used as flow tracers, and digitally acquired backscattered RF-data are used with custom velocimetry analysis to obtain velocity vectors. The technique has been shown as useful in obtaining 2D flow velocity from various flow patterns, including blood flow. Well control of timely sensitive microbubble concentration in Echo PIV is very important to produce robust data quality. In this paper, effect of microbubble concentration on Echo PIV data quality was examined and a quantitative tool based on feature of Echo PIV image cross-correlation was developed to evaluate real time robustness of Echo PIV data quality induced by bubble concentration and image quality

The South Asian Origins of the Global Network to Eradicate Blindness: WHO, NGOs, and Decentralization

The global network to eradicate blindness emerged out of the work of Western and South Asian professionals to eradicate smallpox which was endemic in South Asia. The history of the emergence of the global network to eradicate blindness demonstrates a shift from vertical command and control public health programs directed by the WHO, to the decentralized public health services originating in non-profit, non-governmental organizations and coordinated by the WHO. The WHO constitution started with a federal regionalist structure that encouraged collaboration and coordination with NGOs. In South Asia in particular, epidemiologists and general medical practitioners moved from eradicating smallpox through the WHO to creating their own domestic and international NGOs based in various countries with a mission to control blindness in South Asia and Africa. In 1975, pushed by the WHO Director General, these new NGOs in turn joined with individual ophthalmologists and existing blind member associations to form the International Agency for the Prevention of Blindness. Thus, the WHO was shaped by, and shaping, international NGOs such as the IAPB. The IAPB pushed for the formation of the WHO Prevention of Blindness program. This was the earliest example of how the IAPB facilitates bottom-up agenda-setting in the WHO. In 1980, when the WHO officially closed the smallpox program, the Prevention of Blindness program first received independent funding. Presently, the IAPB acts as a decentralized arm of the WHO.

Unconfined compression of porcine ocular lenses: Experiments and finite element analysis

Understanding the mechanics of lens accommodation (ability of the eye dynamically to focus near to far, or far to near) can assist in the diagnosis of early presbyopia as well as identify potential clinical treatments and lens prosthetic implantation strategies [1–3]. Related to the mechanism of focusing, presbyopia is an ocular disease that stems from age-related loss of lens accommodation leading to a loss of focusing range and near vision [4]. This is attributed to changes in ciliary muscle function, as well as changes in the mechanical properties of the lens substance, lens capsule, and zonules, presumably. The precise relationship of these changes, however, is not well described. The location of the lens in the eye is shown in Fig.1 [5].Copyright

1J-2 Development of a Customized Echo Particle Image Velocimetry System for Real Time Multi-component Hemodynamics Measurements: System Characterization and Initial Experiments

The measurement of multi-component temporal blood velocity and shear stress distributions in the cardiovascular system is important in hemodynamic evaluation of patients with various cardiovascular diseases since changes in local flow patterns may reflect development and progression of pathology. Here, we report on a custom designed echo particle image velocimetry (Echo PIV) system, with improved dynamic velocity range and spatial resolution over prior systems, to perform real time non-invasive measurement of multi-dimensional velocity and shear stress components in arteries and hearts by identifying and tracking flow tracers (ultrasound contrast microbubbles) within the flow fields. The customized Echo PIV system was developed with a novel linear ultrasound array transducer (128 elements, 7.5 MHz center frequency, 73% bandwidth), a custom-controllable signal processing system and custom PIV analysis. The maximum achievable frame rate of the system is 1786 fps, which allows maximum velocities up to 2.14 m/s to be measured. Initial in vitro measurements were made on pipe flows, simulating flow in blood vessels and in vitro models simulating abdominal aortic aneurysms (AAA). Ultrasound Doppler measurements of peak velocity were also taken in the pipe flow studies for comparison. Echo PIV measured velocities agreed well with Doppler measurements with a maximum deviation of 3.6%. The Echo PIV system also captured successfully the vortex rings in AAA models and the corresponding shear stress distributions in these flow fields. Such multi-component velocity measurements are clinically unfeasible using conventional ultrasound Doppler flow imaging