Medical engineering & physics
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Titanium flexible intramedullary nails have become far more prevalent for stabilization of pediatric femur fractures in recent years. While steel may be expected to have superior fracture stability due to its higher elastic modulus; titanium alloy has experimentally demonstrated improved biomechanical stability, as measured by gap closure and nail slippage. The purpose of this study was to verify these observations computationally, and thus, explain why titanium alloy may be better suited for surgical fixation of fractured femurs. ⋯ These results agree with previously published clinical and biomechanical studies that reported increased gap closure and nail slippage with stainless steel nails. The increased deformation of the titanium alloy nail likely increases the contact area with the intramedullary canal wall, thus, increasing stability. Additionally, stainless steel nails had higher curve apex von Mises stresses, potentially inducing a stress-shielding effect which could hamper remodeling and consequently increase risk of re-fracture.
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A new wavelet-based method for the compression of electrocardiogram (ECG) data is presented. A discrete wavelet transform (DWT) is applied to the digitized ECG signal. ⋯ An adaptive arithmetic coder with several different context models is employed for the entropy coding of these symbol streams. Simulation results on several records from the MIT-BIH arrhythmia database show that the proposed coding algorithm outperforms some recently developed ECG compression algorithms.
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Error propagation and word-length-growth are two intrinsic effects influencing the performance of wavelet-based ECG data compression methods. To overcome these influences, a non-recursive 1-D discrete periodized wavelet transform (1-D NRDPWT) and a reversible round-off linear transformation (RROLT) theorem are developed. The 1-D NRDPWT can resist truncation error propagation in decomposition processes. ⋯ This algorithm supplies high and low octave coefficients with small and large decimal quantization scales, respectively. Evaluation is based on the percentage root-mean-square difference (PRD) performance measure, the maximum amplitude error (MAE), and visual inspection of the reconstructed signals. By using the MIT-BIH arrhythmia database, the experimental results show that this new approach can obtain a superior compression performance, particularly in high CR situations.
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An automated loading and measurement device has been developed for assessment of the mechanical properties of a healing human tibial fracture. The characteristics of the device are presented with assessments of errors. This paper constitutes a small part of a long term research project determining a clinically quantifiable end point for fracture healing in humans, hence a sample of results is presented to demonstrate the potential application of the device. ⋯ The results from this work support the view that fracture stiffness should be measured in at least two planes. A new material property for the assessment of fracture healing, the gamma ratio gamma, is examined and preliminary results are shown. The paper also demonstrates how creep properties of a healing tibia can be assessed and proposes that this property may form the basis for future fracture assessment investigations.
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This study focuses on the effect of the temperature response of a semi-infinite biological tissue due to a sinusoidal heat flux at the skin. The Pennes bioheat transfer equation such as rho(t)c(t)( partial differentialT/ partial differentialt)+W(b)c(b)(T-T(a))=k partial differential(2)T/ partial differentialx(2) with the oscillatory heat flux boundary condition such as q(0,t)=q(0)e(iomegat) was investigated. By using the Laplace transform, the analytical solution of the Pennes bioheat transfer equation with surface sinusoidal heating condition is found. ⋯ The results show that the temperature oscillation due to the sinusoidal heating on the skin surface is unstable in the initial period. Further, it is unavailable to predict the blood perfusion rate via the phase shifting between the surface heat flux and the surface temperature. Moreover, the lower frequency of sinusoidal heat flux on the skin surface induces a more sensitive phase shift response to the blood perfusion rate change, but extends the beginning time of sampling because of the avoidance of the unavailable first cyclic oscillation.