Laser-generated ultrasound with optical fibres using functionalised carbon nanotube composite coatings

Optical ultrasound transducers were created by coating optical fibres with a composite of carbon nanotubes (CNTs) and polydimethylsiloxane (PDMS). Dissolution of CNTs in PDMS to create the composite was facilitated by functionalisation with oleylamine. Composite surfaces were applied to optical fibres using dip coating. Under pulsed laser excitation, ultrasound pressures of 3.6 MPa and 4.5 MPa at the coated end faces were achieved with optical fibre core diameters of 105 and 200 μm, respectively. The results indicate that CNT-PDMS composite coatings on optical fibres could be viable alternatives to electrical ultrasound transducers in miniature ultrasound imaging probes

Ultrasensitive plano-concave optical microresonators for ultrasound sensing

Highly sensitive broadband ultrasound detectors are needed to expand the capabilities of biomedical ultrasound, photoacoustic imaging and industrial ultrasonic non-destructive testing techniques. Here, a generic optical ultrasound sensing concept based on a novel plano-concave polymer microresonator is described. This achieves strong optical confinement (Q-factors > 105) resulting in very high sensitivity with excellent broadband acoustic frequency response and wide directivity. The concept is highly scalable in terms of bandwidth and sensitivity. To illustrate this, a family of microresonator sensors with broadband acoustic responses up to 40 MHz and noise-equivalent pressures as low as 1.6 mPa per √Hz have been fabricated and comprehensively characterized in terms of their acoustic performance. In addition, their practical application to high-resolution photoacoustic and ultrasound imaging is demonstrated. The favourable acoustic performance and design flexibility of the technology offers new opportunities to advance biomedical and industrial ultrasound-based techniques

Counterparts: Clothing, value and the sites of otherness in Panapompom ethnographic encounters

This is an Author's Accepted Manuscript of an article published in Anthropological Forum, 18(1), 17-35, 2008 [copyright Taylor & Francis], available online at: http://www.tandfonline.com/10.1080/00664670701858927.Panapompom people living in the western Louisiade Archipelago of Milne Bay Province, Papua New Guinea, see their clothes as indices of their perceived poverty. ‘Development’ as a valued form of social life appears as images that attach only loosely to the people employing them. They nevertheless hold Panapompom people to account as subjects to a voice and gaze that is located in the imagery they strive to present: their clothes. This predicament strains anthropological approaches to the study of Melanesia that subsist on strict alterity, because native self‐judgments are located ‘at home’ for the ethnographer. In this article, I develop the notion of the counterpart as a means to explore these forms of postcolonial oppression and their implications for the ethnographic encounter

Exclusion and reappropriation: Experiences of contemporary enclosure among children in three East Anglian schools

Transformations of the landscapes which children inhabit have significant impacts on their lives; yet, due to the limited economic visibility of children’s relationships with place, they have little stake in those transformations. Their experience, therefore, illustrates in an acute way the experience of contemporary enclosure as a mode of subordination. Following fieldwork in three primary schools in South Cambridgeshire, UK, we offer an ethnographic account of children’s experiences of socio-spatial exclusion. Yet, we suggest that such exclusion is by no means an end-point in children’s relationships with place. Challenging assumptions that children are disconnected from nature, we argue that through play and imaginative exploration of their environments, children find ways to rebuild relationships with places from which they find themselves excluded. This is the author accepted manuscript. The final version is available from SAGE via http://dx.doi.org/10.1177/026377581664194

Real-time and Freehand Multimodal Imaging: Combining White Light Endoscopy with All-Optical Ultrasound

Minimally invasive surgery offers significant benefits over open surgery in terms of patient recovery, complication rates, and cost. Accurate visualisation is key for successful interventions; however, no single imaging modality offers sufficient resolution, penetration, and soft-tissue contrast to adequately monitor interventional treatment. Consequently, multimodal interventional imaging is intensively investigated. All-optical ultrasound (AOUS) imaging is an emerging modality where light is used to both generate and detect ultrasound. Using fibre-optics, highly miniaturised imaging probes can be fabricated that yield high-quality pulse-echo images and are readily integrated into minimally invasive interventional instruments. In this work, we present the integration of a miniature (diameter: 800 µm), highly directional AOUS imaging probe into a commercially available white light urethroscope, and demonstrate the first real-time, 3D multimodal imaging combining AOUS and white light endoscopy. Through the addition of an electromagnetic tracker, the position and pose of the instrument could be continuously recorded. This facilitated accurate real-time registration of the imaging modalities, as well as freehand operation of the instrument. In addition, the freehand imaging paradigm allowed for “piece-wise” scanning where the instrument was retracted and repositioned without recalibration. The presented imaging probe and system could significantly improve the quality of image guidance during interventional surgery

Robot-assisted Optical Ultrasound Scanning

Optical ultrasound, where ultrasound is both generated and received using light, can be integrated in very small diameter instruments making it ideally suited to minimally invasive interventions. One-dimensional information can be obtained using a single pair of optical fibres comprising of a source and detector but this can be difficult to interpret clinically. In this paper, we present a robotic-assisted scanning solution where a concentric tube robot manipulates an optical ultrasound probe along a consistent trajectory. A torque coil is utilised as a buffer between the curved nitinol tube and the probe to prevent torsion on the probe and maintain the axial orientation of the probe while the tube is rotating. The design and control of the scanning mechanism are presented along with the integration of the mechanism with a fibre-based imaging probe. Trajectory repeatability is assessed using electromagnetic tracking and a technique to calibrate the transformation between imaging and robot coordinates using a known model is presented. Finally, we show example images of 3D printed phantoms generated by collecting multiple OpUS A-scans within the same 3D scene to illustrate how robot-assisted scanning can expand the field of view

Optical fiber laser ultrasound transmitter with electrospun composite for minimally invasive medical imaging

We report an optical fiber ultrasound transmitter with electrospun MWCNT-polymer composite, generating high-amplitude broadband ultrasound. They produced pressures in the range of conventional intravascular imaging transducers, and can be incorporated into catheters/needles for keyhole surgery

Measurement of Liver Blood Flow: A Review

The study of hepatic haemodynamics is of importance in understanding both hepatic physiology and disease processes as well as assessing the effects of portosystemic shunting and liver transplantation. The liver has the most complicated circulation of any organ and many physiological and pathological processes can affect it1,2. This review surveys the methods available for assessing liver blood flow, examines the different parameters being measured and outlines problems of applicability and interpretation for each technique