9 research outputs found
Simulation of biopsy bevel-tipped needle insertion into soft-gel
Planning and practice of surgical procedures can be improved through the use of modelling. This study provides an insight into the biopsy needle (i.e. hollow cannula) and needle-tissue interactions using a modelling approach, thus enabling the optimization of needle-tip designs not only for training but also for the planning of surgical procedures. Simulations of needle insertion into agar gel were performed using a Coupled Eulerian-Lagrangian (CEL) based finite element (FE) analysis, adapted for large deformation and tissue fracture. The experimental work covers needle insertion into 3% agar gel using a needle with a beveled tip of various angles, to assess the validity of the simulation. The simulated needle deflection and insertion force for two needles (i.e. Needle 1 with 18° bevel angle and Needle 2 with 27° bevel angle) were compared with corresponding experimental results. The contact stress (i.e. contact pressure) on the needles from the agar gel during the insertion of the needles were also studied. Observations indicate that varying the needle bevel angle from 27° to 18° results in a decrease of the peak force (i.e. puncture force) and an increase in needle deflection. Quantitatively, the percentage errors between the experimental data and the FE model for the total insertion force along the z-direction (i.e. Z Force) for Needle 1 and 2 were 4% and 4.8% (p > 0.05), respectively. Similarly, needle deflection percentage errors along the x-z plane were 5.7% and 10% respectively. Therefore, the forces and needle deflection values predicted by the simulation are a close approximation of the experimental model, validating the Coupled Eulerian-Lagrangian based FE model. Thus, providing an experimentally validated model for biopsy and cytology needle design in silico that has the potential to replace the current build and break approach of needle design used by manufacturers
Doubling the far-field resolution in midinfrared microscopy
The spatial resolution in far-field mid-infrared (λ>2.5 μm) microscopy and microspectroscopy
remains limited with the full-width at half maximum of the point-spread
function ca. λ/1.3; a value that is very poor in comparison to that commonly accessible with
visible and near-infrared optics. Hereafter, it is demonstrated however that polymer beads that
are centre-to-centre spaced by λ/2.6 can be resolved in the mid-infrared. The more than 2-fold
improvement in resolution in the far-field is achieved by exploiting a newly constructed
scanning microscope built around a mid-infrared optical parametric oscillator and a central
solid-immersion lens, and by enforcing the linear polarization unidirectional resolution
enhancement with a novel and robust specimen error minimization based on a particle swarm
optimization. The method is demonstrated with specimens immersed in air and in water, and
its robustness shown by the analysis of dense and complex self-assembled bead islands
Polarisation changes in guided infrared thermography using silver halide poly-crystalline mid-infrared fibre bundle
Broadband mid-infrared (B-MIR) thermography using fibre optic waveguides can be critical in real-time imaging in harsh environments such as additive manufacturing, personalised medical diagnosis and therapy. We investigate the polarisation effect on thermal measurements through poly-crystalline fibre bundle employing a simple broadband cross-polarisation configuration experimental set-up. Silver halide poly-crystalline fibres AgCl1-xBrx (0 = x=1) (AgClBr-PolyC) have very wide transmission bandwidth spanning over the spectral range from 1 µm up to 31 µm FWHM. Moreover, they are non-toxic, nonhygroscopic, with relatively good flexibility, which make them very adequate for spectroscopic and thermal measurements in medical and clinical fields. In this study, we used a fibre bundle composed of seven single AgClBr-PolyC fibres, each with a core diameter of about 300 µm, inserted between two broadband MIR polarisers.A silicon carbide filament source was placed at the entrance of the fibre bundle, while a FLIR thermal camera with a close-up lens was employed to measure the spatial temperature distribution over the fibre-bundle end. Indeed, polarisation dependence of temperature measurements has been clearly observed in which the orientation of temperature extrema (minima and maxima)vary from one fibre to another within the bundle. Moreover, these observations have enabled the classification of AgClBr-PolyC
fibres following their polarisation sensitivities by which some fibres are relatively highly
sensitive to polarisation with polarisation temperature difference (PTD) that can reach
22.1 ± 2.8 °C, whereas some others show very low PTD values down to 3.1 ± 2.8 °C. Many applications can readily be found based on the advantages of both extreme cases
Spatial-domain filter enhanced subtraction microscopy and application to mid-IR imaging
We have experimentally investigated the enhancement in spatial resolution by image subtraction in mid-infrared central solid-immersion lens (c-SIL) microscopy. The subtraction exploits a first image measured with the c-SIL point-spread function (PSF) realized with a Gaussian beam and a second image measured with the beam optically patterned by a silicon it-step phase plate, to realize a centrally hollow PSF. The intense sides lobes in both PSFs that are intrinsic to the SIL make the conventional weighted subtraction methods inadequate. A spatial-domain filter with a kernel optimized to match both experimental PSFs in their periphery was thus developed to modify the first image prior to subtraction, and this resulted in greatly improved performance, with polystyrene beads 1.4 0.1 mu m apart optically resolved with a mid-1R wavelength of 3.4 mu m in water. Spatial-domain filtering is applicable to other PSF pairs, and simulations show that it also outperforms conventional subtraction methods for the Gaussian and doughnut beams widely used in visible and near-1R microscopy. (C) 2017 Optical Society of Americ
Circular polarization conversion in single plasmonic spherical particles
Temporal and spectral behaviors of plasmons determine their ability to enhance the characteristics of metamaterials tailored to a wide range of applications, including electric-field enhancement, hot-electron injection, sensing, as well as polarization and angular momentum manipulation. We report a dark-field (DF) polarimetry experiment on single particles with incident circularly polarized light in which gold nanoparticles scatter with opposite handedness at visible wavelengths. Remarkably, for silvered nanoporous silica microparticles, the handedness conversion occurs at longer visible wavelengths, only after adsorption of molecules on the silver. Finite element analysis (FEA) allows matching the circular polarization (CP) conversion to dominant quadrupolar contributions, determined by the specimen size and complex susceptibility. We hypothesize that the damping accompanying the adsorption of molecules on the nanostructured silver facilitates the CP conversion. These results offer new perspectives in molecule sensing and materials tunability for light polarization conversion and control of light spin angular momentum at submicroscopic scale.</p
Image-based tracking of anticancer drug-loaded nanoengineered polyelectrolyte capsules in cellular environments using a fast Benchtop Mid-Infrared (MIR) microscope
Drug delivery monitoring and tracking in the
human body are two of the biggest challenges in targeted
therapy to be addressed by nanomedicine. The ability of
imaging drugs and micro-/nanoengineered drug carriers and of
visualizing their interactions at the cellular interface in a labelfree
manner is crucial in providing the ability of tracking their
cellular pathways and will help understand their biological
impact, allowing thus to improve the therapeutic efficacy. We
present a fast, label-free technique to achieve high-resolution
imaging at the mid-infrared (MIR) spectrum that provides
chemical information. Using our custom-made benchtop
infrared microscope using a high-repetition-rate pulsed laser (80 MHz, 40 ps), we were able to acquire images with
subwavelength resolution (0.8 × λ) at very high speeds. As a proof-of-concept, we embarked on the investigation of
nanoengineered polyelectrolyte capsules (NPCs) containing the anticancer drug, docetaxel. These NPCs were synthesized using
a layer-by-layer approach built upon a calcium carbonate (CaCO3) core, which was then removed away with
ethylenediaminetetraacetic acid. The obtained MIR images show that NPCs are attached to the cell membrane, which is a
good step toward an efficient drug delivery. This has been confirmed by both three-dimensional confocal fluorescence and
stimulated emission depletion microscopy. Coupled with additional instrumentation and data processing advancements, this
setup is capable of video-rate imaging speeds and will be significantly complementing current super-resolution microscopy
techniques while providing an unperturbed view into living cells