Current Issue : January - March Volume : 2013 Issue Number : 1 Articles : 5 Articles
Image segmentation is an important task involved in different areas from image processing to image analysis.\r\nOne of the simplest methods for image segmentation is thresholding. However, many thresholding methods are\r\nbased on a bi-level thresholding procedure. These methods can be extended to form multi-level thresholding, but they\r\nbecome computationally expensive because a large number of iterations would be required for computing the optimum\r\nthreshold values. In order to overcome this disadvantage, a new method based on a Shrinking Search Space (3S)\r\nalgorithm is proposed in this paper. The method is applied on statistical bi-level thresholding approaches including\r\nEntropy, Cross-entropy, Covariance, and Divergent Based Thresholding (DBT), to achieve multi-level thresholding and\r\nused for intracranial segmentation from brain MRI images. The paper demonstrates that the impact of the proposed\r\n3S technique on the DBT method is more significant than the other bi-level thresholding approaches. Comparing the\r\nresults of using the proposed approach against those of the Fuzzy C-Means (FCM) clustering method demonstrates\r\na better segmentation performance by improving the similarity index from 0.58 in FCM to 0.68 in the 3S method. Also,\r\nthis method has a lower computation complexity of around 0.37s with respect to 157s processing time in FCM. In\r\naddition, the FCM approach does not always guarantee the convergence, whilst the 3S technique always converges\r\nto the optimum res....
Background: The paper presents a newly researched acoustic system for blood\r\nvolume measurements for the developed family of Polish ventricular assist devices.\r\nThe pneumatic heart-supporting devices are still the preferred solution in some\r\ncases, and monitoring of their operation, especially the temporary blood volume, is\r\nyet to be solved.\r\nMethods: The prototype of the POLVAD-EXT prosthesis developed by the\r\nFoundation of Cardiac Surgery Development, Zabrze, Poland, is equipped with the\r\nnewly researched acoustic blood volume measurement system based on the\r\nprinciple of Helmholtz�s acoustic resonance. The results of static volume\r\nmeasurements acquired using the acoustic sensor were verified by measuring the\r\nvolume of the liquid filling the prosthesis. Dynamic measurements were conducted\r\non the hybrid model of the human cardiovascular system at the Foundation, with the\r\nTransonic T410 (11PLX transducer - 5% uncertainty) ultrasound flow rate sensor, used\r\nas the reference.\r\nResults: The statistical analysis of a series of static tests have proved that the sensor\r\nsolution provides blood volume measurement results with uncertainties (understood\r\nas a standard mean deviation) of less than 10%. Dynamic tests show a high\r\ncorrelation between the results of the acoustic system and those obtained by flow\r\nrate measurements using an ultrasound transit time type sensor.\r\nConclusions: The results show that noninvasive, online temporary blood volume\r\nmeasurements in the POLVAD-EXT prosthesis, making use of the newly developed\r\nacoustic system, provides accurate static and dynamic measurements results.\r\nConducted research provides the preliminary view on the possibility of reducing the\r\nadditional sensor chamber volume in future....
Background: It has been proposed that in the absence of a blood supply, the ocular\r\nlens operates an internal microcirculation system. This system delivers nutrients,\r\nremoves waste products and maintains ionic homeostasis in the lens. The\r\nmicrocirculation is generated by spatial differences in membrane transport\r\nproperties; and previously has been modelled by an equivalent electrical circuit and\r\nsolved analytically. While effective, this approach did not fully account for all the\r\nanatomical and functional complexities of the lens. To encapsulate these\r\ncomplexities we have created a 3D finite element computer model of the lens.\r\nMethods: Initially, we created an anatomically-correct representative mesh of the\r\nlens. We then implemented the Stokes and advective Nernst-Plank equations, in\r\norder to model the water and ion fluxes respectively. Next we complemented the\r\nmodel with experimentally-measured surface ionic concentrations as boundary\r\nconditions and solved it.\r\nResults: Our model calculated the standing ionic concentrations and electrical\r\npotential gradients in the lens. Furthermore, it generated vector maps of intra- and\r\nextracellular space ion and water fluxes that are proposed to circulate throughout\r\nthe lens. These fields have only been measured on the surface of the lens and our\r\ncalculations are the first 3D representation of their direction and magnitude in the\r\nlens.\r\nConclusion: Values for steady state standing fields for concentration and electrical\r\npotential plus ionic and fluid fluxes calculated by our model exhibited broad\r\nagreement with observed experimental values. Our model of lens function\r\nrepresents a platform to integrate new experimental data as they emerge and assist\r\nus to understand how the integrated structure and function of the lens contributes\r\nto the maintenance of its transparency....
Background: Micro bubbles were initially introduced as contrast agents for\r\nultrasound examinations as they are able to modify the signal-to-noise ratio in\r\nimaging, thus improving the assessment of clinical information on human tissue.\r\nRecent developments have demonstrated the feasibility of using these bubbles as\r\ndrug carriers in localized delivery. In micro fluidics devices for generation of micro\r\nbubbles, the bubbles are formed at interface of liquid gas through a strangulation\r\nprocess. A device that uses these features can produce micro bubbles with small size\r\ndispersion in a single step.\r\nMethods: A T-junction micro fluidic device constructed using 3D prototyping was\r\nmade for the production of mono dispersed micro bubbles. These micro bubbles\r\nuse sunflower oil as a lipid layer. Stability studies for micro bubbles with diameters\r\ndifferent generated from a liquid phase of the same viscosity were conducted to\r\nevaluate whether micro bubbles can be used as drug carriers. The biocompatibility\r\nof coating layer, the ability to withstand environmental pressure variations combined\r\nwith echogenicity, are key factors that they can safely play the role of drug\r\ntransporters.\r\nResults: The normal distribution curve with small dispersion of the diameter of\r\nbubbles validates the process of generating micro bubbles with low value of\r\nvariation coefficient, i.e., 0.381 at 1.90%. The results also showed the feasibility of\r\nusing sunflower oil as the lipid matrix with stable population of bubbles over\r\n217 minutes for micro bubbles with an average diameter of 313.04 �µm and\r\n121 minutes for micro bubbles with an average diameter of 73.74 �µm, considering\r\nbubbles with air as gaseous phase.\r\nConclusion: The results indicate that the micro fluidic device designed can be used\r\nfor producing micro bubbles with low variation coefficient using sunflower oil as a\r\ncoating of micro bubbles. These carriers were stable for periods of time that are long\r\nenough for clinical applications even when regular air is used as the gas phase.\r\nImproved stability can be achieved when biocompatible gas with lower permeability\r\nis used....
Objective: The objective of this study was to test a newly developed implant for the treatment of intertrochanteric\r\nfractures, the X-Bolt, against the current gold standard, the Dynamic Hip Screw (DHS), by comparing the amount of\r\nenergy required to cause failure of both of them.\r\nMethods: Push out studies were performed with both the dynamic hip screw and the X-Bolt in an artificial bone\r\nsubstrate in the form of polyurethane foam blocks, which have predefined mechanical properties. These push out\r\nstudies were performed as a means to investigate each implants resistance to ââ?¬Ë?cut outââ?¬â?¢ as this is the most common\r\nmode of failure with the DHS.\r\nResults: The results demonstrate that the X-Bolt produced a force displacement curve with a different pattern of\r\nfailure than the DHS. The X-Bolt initially required less energy to move it within the test material, than the DHS. However,\r\nthe further the X-Bolt advanced within the test material, the greater the resistance and as this was the opposite as to\r\nwhat occurred with the DHS, the X-Bolt eventually required more energy than the DHS to advance through the test\r\nmaterial and fail due ââ?¬Ë?cut outââ?¬â?¢.\r\nConclusion: The X-Bolt is a new concept with regard to fixation of intertrochanteric fractures. It produces a different\r\nforce displacement curve than the dynamic hip screw. However further investigations are necessary before the true\r\npotential of this new implant is known....
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