Current Issue : January - March Volume : 2015 Issue Number : 1 Articles : 5 Articles
Background: In ultrasound elastography, reconstruction of tissue elasticity\n(e.g., Youngâ��s modulus) requires regularization and known information of forces\nand/or displacements on tissue boundaries. In practice, it is challenging to choose an\nappropriate regularization parameter; and the boundary conditions are difficult to\nobtain in vivo. The purpose of this study is to develop a more applicable algorithm that\ndoes not need any regularization or boundary force/displacement information.\nMethods: The proposed method adopts the bicubic B-spline as the tissue motion\nmodel to estimate the displacement fields. Then the estimated displacements are input\nto the finite element inversion scheme to reconstruct the Youngâ��s modulus of each\nelement. In the inversion, a modulus boundary condition is used instead of force/\ndisplacement boundary conditions. Simulation and experiments on tissue-mimicking\nphantoms are carried out to test the proposed method.\nResults: The simulation results demonstrate that Youngâ��s modulus reconstruction of the\nproposed method has a relative error of ?3.43 �± 0.43% and root-squared-mean error of\n16.94 �± 0.25%. The phantom experimental results show that the target hardening artifacts\nin the strain images are significantly reduced in the Youngâ��s modulus images. In both\nsimulation and phantom studies, the size and position of inclusions can be accurately\ndepicted in the modulus images.\nConclusions: The proposed method can reconstruct tissue Youngâ��s modulus distribution\nwith a high accuracy. It can reduce the artifacts shown in the strain image and correctly\ndelineate the locations and sizes of inclusions. Unlike most modulus reconstruction\nmethods, it does not need any regularization during the inversion procedure.\nFurthermore, it does not need to measure the boundary conditions of displacement or\nforce. Thus this method can be used with a freehand scan, which facilitates its usage in\nthe clinic....
Background: Disorders associated with excessive swelling of the lower extremities are\ncommon. They can be associated with pain, varicose veins, reduced blood pressure\nwhen standing and may cause syncope or fainting. The common physical remedy to\nthese disorders is the use of compression stockings and pneumatic compression leg\nmassagers, which both attempt to limit blood pooling and capillary filtration in the\nlower limbs. However, compression stockings provide a constant pressure, and their\nefficiency has been challenged according to some recent studies. Air compression leg\nmassagers on the other hand, restricts patient mobility. In this work we therefore\npresent an innovative active compression bandage based on the use of a smart\nmaterials technology that could produce intermittent active pressure to mitigate the\nsymptoms of lower extremity disorders.\nMethods: An active compression bandage (ACB), actuated by shape memory alloy\n(SMA) wires, was designed and prototyped. The ACB was wrapped around a calf model\nto apply an initial pressure comparable to the one exerted by commercial compression\nstockings. The ACB was controlled to apply different values of compression. A data\nacquisition board and a LabVIEW program were used to acquire both the pressure data\nexerted by the ACB and the electrical current required to actuate the SMA wires. An\nanalytical model of the ACB based on a SMA constitutive model was developed. An\noptimizer was implemented to identify optimal parameters of the model to best\nestimate the performance of the ACB.\nResults: The maximum increase in pressure due to the SMA wires activation was\n40.8% higher than the initially applied pressure to the calf model. The analytical model\nof the ACB estimated the behaviour of the ACB with less than 0.32 mmHg difference\nwith the experimental results.\nConclusions: The prototyped ACB was able to apply an initial compression\ncomparable to the one applied by commercial compression stockings. Activation of\nthe ACB resulted in an increase of compression up to 9.06 mmHg. Comparison\nbetween analytical and experimental results showed the analytical model was suitable\nto predict the behaviour of the ACB...
Background: Understanding of kinematics force applied at the elbow is important\nin many fields, including biomechanics, biomedical engineering and rehabilitation.\nThis paper provides a comparison of a mathematical model of elbow joint using\nthree different types of prosthetics for transhumeral user, and characterizes the forces\nrequired to overcome the passive mechanical of the prosthetics at the residual limb.\nMethods: The study modeled the elbow as a universal joint with intersecting axes of\nx-axis and y-axis in a plain of upper arm and lower arm. The equations of force applied,\ntorque, weight and length of different type of prosthetics and the anthropometry of\nprosthetics hand are discussed in this study. The study also compares the force, torque\nand pressure while using all three types of prosthetics with the normal hand.\nResults: The result was measured from the elbow kinematics of seven amputees, using\nthree different types of prosthetics. The F-Scan sensor used in the study is to determine\nthe pressure applied at the residual limb while wearing different type of prostheses.\nConclusion: These technological advances in assessment the biomechanics of an\nelbow joint for three different type of prosthetics with the normal hand bring the new\ninformation for the amputees and prosthetist to choose the most suitable device to be\nworn daily....
Background: The current study aimed to compare the measurements of the mandible\nmorphology using 3D cone beam computed tomography (CBCT) images with those\nusing 2D CBCT-synthesized cephalograms; to quantify errors in measurements based\non 2D synthesized cephalograms; and to clarify the effects such errors have on the\ndescription of the mandibular growth.\nMethods: Mandibles of six miniature pigs were scanned monthly using CBCT over\n12 months and the data were used to reconstruct the 3D bone models. Five anatomical\nlandmarks were identified on each bone model, and the inter-marker distances and\nmonthly distance changes were calculated and taken as the gold standard. Synthetic 2D\ncephalograms were also generated for each bone model using a digitally reconstructed\nradiography (DRR)-generation method. Errors in cephalogram measurements were\ndetermined as the differences between the calculated variables in cephalograms and the\ngold standard. The variations between cephalograms and the gold standard were also\ncompared using paired t-tests.\nResults: While the inter-marker distance increases varied among the marker pairs, all\nmarker pairs increased their inter-marker distances gradually every month, reaching 50%\nof the total annual increases during the fourth and fifth months, and then slowing down\nin the subsequent months. The 2D measurements significantly underestimated most of\nthe inter-marker distances throughout the monitoring period, in most of the monthly\ninter-marker distance changes during the first four months, and in the total growth\n(p <0.05).\nConclusions: Significant errors exist in the measurements using 2D synthesized\ncephalogram, underestimating the mandibular dimensions and their monthly changes in\nthe early stages of growth, as well as the total annual growth. These results should be\nconsidered in dental treatment planning at the beginning of the treatment in order to\ncontrol more precisely the treatment process and outcome....
Background: Impedance plethysmography applied to the head by using a pair of\nelectrodes attached to the scalp surface is known as bipolar Rheoencephalography\nor REG I and was originally proposed to measure changes in cerebral blood volume\nrelated to the heartbeat. REG I was soon discarded in favor of other REG\nconfigurations, since most of the signal was shown to be heavily contaminated by\nthe extracranial blood flow. The main goal of this study was to identify and compare\nthe part of the REG I signal caused by scalp blood flow with that originating from\nnon-extracranial sources.\nMethods: A clinical study involving thirty-six healthy volunteers was designed for\nthis purpose. REG I was first registered in each subject under normal conditions.\nA pneumatic cuff was then placed around the head and was inflated to arrest the\nscalp blood flow and a second REG I was recorded. Finally, a third REG I was taken\nimmediately after cuff deflation.\nResults: The REG I signal is attenuated, but not extinguished, during cuff inflation in\na wide subject-dependent range ratio from 0.12 to 0.68 (0.37 �± 0.15). The residual\nREG I signal has a waveform that is markedly different from that obtained before cuff\ninflation, which supports the hypothesis of the intracranial origin of the residual REG\nI signal. Additionally, an increase of 22% in REG I amplitude was observed when the\nhead cuff was deflated.\nConclusions: Waveform differences between extra and non-extracranial components\nare significant and these differences could be used in a method to distinguish\none from the other. However, a significant part of the REG I signal is caused by\na non-extracranial source and, therefore, it should not be used as a footprint of\nthe extracranial blood flow....
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