408 research outputs found
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 Âľm), 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 âpiece-wiseâ
scanning where the instrument was retracted and repositioned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
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 3.6âMPa and 4.5âMPa at the coated end faces were achieved with optical fibre core diameters of 105 and 200âÎźm, 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
Acoustical characterisation of carbon nanotube-loaded polydimethylsiloxane used for optical ultrasound generation
An optical ultrasound generator was used to perform broadband (2-35 MHz) acoustical characterisation measurements of a nanocomposite comprising carbon nanotubes (CNT) and polydimethylsiloxane (PDMS), a composite that is commonly used as optical ultrasound generator. Samples consisting of either pure PDMS or CNT-loaded PDMS were characterised to determine the influence of CNTs on the speed of sound and power-law acoustic attenuation parameters. A small weight fraction (<; 1.8%) of added CNTs was found to yield a prominent increase in the exponent of the power law, resulting in a significant increase in acoustic attenuation at higher frequencies. The speed of sound was found to be nearly identical, however. These results could prove useful in the numerical modelling and design of future optical ultrasound sources based on CNT-loaded PDMS
Comparison of Fabrication Methods for FiberâOptic Ultrasound Transmitters Using CandleâSoot Nanoparticles
Candle-soot nanoparticles (CSNPs) have shown great promise for fabricating optical ultrasound (OpUS) transmitters. They have a facile, inexpensive synthesis whilst their unique, porous structure enables a fast heat diffusion rate which aids high-frequency ultrasound generation necessary for high-resolution clinical imaging. These composites have demonstrated high ultrasound generation performance showing clinically relevant detail, when applied as macroscale OpUS transmitters comprising both concave and planar surfaces, however, less research has been invested into the translation of this material's technology to fabricate fiber-optic transmitters for image guidance of minimally invasive interventions. Here, are reported two fabrication methods of nanocomposites composed of CSNPs embedded within polydimethylsiloxane (PDMS) deposited onto fiber-optic end-faces using two different optimized fabrication methods: âAll-in-Oneâ and âDirect Deposition.â Both types of nanocomposite exhibit a smooth, black domed structure with a maximum dome thickness of 50 Âľm, broadband optical absorption (>98% between 500 and 1400 nm) and both nanocomposites generated high peak-to-peak ultrasound pressures (>3 MPa) and wide bandwidths (>29 MHz). Further, high-resolution (<40 Âľm axial resolution) B-mode ultrasound imaging of ex vivo lamb brain tissue demonstrating how CSNP-PDMS OpUS transmitters can allow for high fidelity minimally invasive imaging of biological tissues is demonstrated
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. âDevelopmentâ 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 selfâjudgments are located âat homeâ 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
- âŚ