31 research outputs found

    Microultrasound characterisation of <i>ex vivo</i> porcine tissue for ultrasound capsule endoscopy

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    Gastrointestinal (GI) disease development and progression is often characterised by cellular and tissue architectural changes within the mucosa and sub-mucosa layers. Current clinical capsule endoscopy and other approaches are heavily reliant on optical techniques which cannot detect disease progression below the surface layer of the tissue. To enhance the ability of clinicians to detect cellular changes earlier and more confidently, both quantitative and qualitative microultrasound (μUS) techniques are investigated in healthy ex vivo porcine GI tissue. This work is based on the use of single-element, focussed μUS transducers made with micromoulded piezocomposite operating at around 48 MHz. To explore the possibility that μUS can detect Crohn's disease and other inflammatory bowel diseases, ex vivo porcine small bowel tissue samples were cannulised and perfused with phosphate-buffered saline followed by various dilutions of polystyrene microspheres. Comparison with fluorescent imaging showed that the microspheres had infiltrated the microvasculature of the samples and that μUS was able to successfully detect this as a mimic of inflammation. Samples without microspheres were analysed using quantitative ultrasound to assess mechanical properties. Attenuation coefficients of 1.78 ± 0.66 dB/mm and 1.92 ± 0.77 dB/mm were obtained from reference samples which were surgically separated from the muscle layer. Six intact samples were segmented using a software algorithm and the acoustic impedance, Z, for varying tissue thicknesses, and backscattering coefficient, BSC, were calculated using the reference attenuation values and tabulated

    Performance of a 50 MHz annular array based imaging system

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    Acoustic tractor beam

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    Investigation of cross talk in kerfless annular arrays for high-frequency imaging

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    The sonic screwdriver

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    When samples of interest are small enough, even the relatively weak forces and torques associated with light can be sufficient for mechanical manipulation, can offer extraordinary position control, and can measure interactions with three orders of magnitude better resolution than atomic force microscopy. However, as the components of interest grow to slightly larger length scales (which may yet be of interest for microfluidic, lab-on-a-chip technologies and for research involving biomedical imaging), other approaches gain strength. This paper includes discussion of the angular momentum carried by sonic beams that we have implemented both to levitate and controllably rotate disks as large as four inches across. Discussion of such acoustic beams complements the discussion of the angular momentum carried by light and, by further analogy, how we view stationary states discussed in quantum mechanics. Hence, a primary use of the sonic screwdriver is as a model system, although these beams are useful for a variety of other reasons as well (not least for aberration correction for ultrasonic array systems). Methods, including the use of holographically structured fields, are discussed
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