Journal of Mechanics in Medicine and Biology

The minimization of errors due to random noise in statistical properties such as the mean and root mean square of a vorticity distribution is investigated. We map two-dimensional (2D) vorticity fields and present the distribution of vorticity with an intensity map. Then, we quantify the reliability of the visualization configuration using statistical properties of this distribution. To validate our methodology, we devise vortical flow fields based on the analytical Lamb–Oseen vortex. The reliability of the vorticity measurements from our results shows that the size of the flow vector sampling and random noise in the data affect the fidelity of the vorticity maps. Based on this analysis, we establish an optimised configuration that minimises the influence of noise on the computed vorticity histograms. The concept outlined in this study may be used to reduce the effects of noise in a vorticity calculation, and thereby improve the effectiveness of flow visualization.

In this paper, a methodological approach to the segmentation of tumours skin lesions in dermoscopy images is presented. Melanoma is the most malignant skin tumor, growing in melanocytes, the cells responsible for pigmentation. This type of cancer is nowadays increasing rapidly, its related mortality rate increases by more modest and inversely proportional to the thickness of the tumor. This rate can be decreased by an earlier detection and better prevention. In dermatoscopic images, the segmentation is essential to characterize the information shape of the lesion and also to locate the tumor for analysis. In this domain, we have evaluated several techniques for the segmentation of dermatoscopic images. All these methods do not exactly separate the lesion from the background. In this work a fast approach in border detection of dermoscopy pigmented skin lesions images based on the region growing algorithm is presented. This method is tested on a set of 60 dermoscopy images. The obtained results show that the presented method achieves both fast and accurate border detection.

Articular cartilage is a vital component of human knee joints by providing a low-friction and wear-resistant surface in knee joints and distributing stresses to tibia. The degeneration or damage of articular cartilage will incur acute pain on the human knee joints. Hence, to understand the mechanism of normal and pathological functions of articular cartilage, it is very important to investigate the contact mechanics of the human knee joints. Experimental research has difficulties in reproducing the physiological conditions of daily activities and measuring the key factors such as contact-stress distributions inside knee joint without violating the physiological environment. On the other hand, numerical approaches such as finite element (FE) analysis provide a powerful tool in the biomechanics study of the human knee joint. This article presents a two-dimensional (2D) FE model of the human knee joints that includes the femur, tibia, patella, quadriceps, patellar tendon, and cartilages. The model is analyzed with dynamic loadings to study stress distribution in the tibia and contact area during contact with or without articular cartilage. The results obtained in this article are very helpful to find the pathological mechanism of knee joint degeneration or damage, and thus guide the therapy of knee illness and artificial joint replacement.

Interaction between articular surfaces at the knee joint allows movement and stability. The knowledge of how this mechanism works in physiological conditions could be very useful for the development of new clinical procedures. The objective of this study was to develop a subject-specific model able to estimate the articular contact area at the tibio-femoral joint avoiding any destructive measurements. Thin plate splines were used to describe articular surfaces and to allow an analytical estimation of the distance between the surfaces. The sensitivity of the model was evaluated and the tibio-femoral contact area was estimated in a living subject. Femoral contact area results were always smaller than the tibial one, whereas tibial contact area results were less repeatable. Increasing the distance threshold, the increase of the contact area was almost linear. High repeatability was obtained sampling each condyle with more than 60 steps. Contact areas, estimated with the loaded knee, were in accordance with physiology and literature showing a good repeatability. The devised model was suitably used to evaluate the articular contact at the knee joint of an healthy living subject and can be a useful clinical tool to suggest procedures aimed at restoring physiological conditions.

A mathematical model is developed for the pulsatile flow of blood through a stenosed tapered artery under the influence of externally imposed body acceleration. The artery is assumed as a cylindrical tube with time-dependent radius having mild stenosis and the non-Newtonian behavior of blood is characterized by generalized Power-law model. The governing equations are transformed by using a radial transformation and solved numerically by a suitable finite difference scheme in order to obtain the velocity, fluid acceleration, wall shear stress, and flow rate. The effect of stenosis severity, tapering, and externally imposed body acceleration on the blood flow in artery is discussed with the help of graph. It is found that all flow characteristics are affected by the stenosis severity, tapering, and periodic acceleration applied on the body.

This paper presents a new approach in the field of electrocardiogram (ECG) feature extraction system based on the discrete wavelet transform (DWT) coefficients using Daubechies Wavelets. Real ECG signals recorded in lead II configuration are chosen for processing. The ECG signal was acquired by a battery operated, portable ECG data acquisition and signal processing module. In the second step the ECG signal was denoised using soft thresholding with Symlet4 wavelet. Further denoising was achieved by removing the corresponding wavelet coefficients at higher levels of decomposition. Later the ECG data files were converted to .txt files and subsequently to. mat files before being imported into the Matlab 7.4.0 environment for the computation of the decomposition coefficients. The QRS complexes were grouped as normal or myocardial ischaemic ones based on these decomposition coefficients. The algorithm developed by us was evaluated with control database comprising 120 records and validated using 60 records making up test database. By using the DWT coefficients, we have successfully achieved the myocardial ischaemia detection rates up to 97.5% with the technique developed by us for control data and up to 100% for validation test data.

Vertebral cement augmentation is rapidly becoming the modality of choice for treating patients who are experiencing severe and persistent pain because of osteoporosis-induced vertebral compression fracture(s). The resulting cement domain (the part of the vertebral body (VB) filled with the cement) has an irregular or complicated shape. In literature reports of finite element analysis (FEA) of models of simulated vertebral cement augmentation, a variety of representations of the shape of the cement domain have been used. In the literature, only very limited attention has been given to the issue of the influence of cement domain shape representation on biomechanical parameters for a given combination of model and loading. This issue is the subject of the present work, with the model being of the L1-L3 motion segments. Augmentation of an unfractured L2 (prophylactic augmentation) was simulated, three cement domain shapes were considered — namely, solid cylinder, with rounded edges; two prolate spheroids; and oblate spheroid — and the applied loading comprised a simultaneous application of a uniform compressive pressure of 0.53 MPa (equivalent to an 800-N compression load) and a counter-clockwise-acting axial rotation moment of 1 Nm to the superior surface of L1. It was found that (1) while the cement domain shape representation has a marked influence on the mean von Mises stress (σ_AVM), the maximum von Mises stress (σ_MVM), and the strain energy density (MSED) distribution in the cement domain, its influence on each of these parameters in each of the biological tissues in the model as well as on the total segmental range of motion is minimal and (2) for σ_AVM and σ_MVM, the lowest value of each of these parameters was obtained when the oblate spheroid model was used. From both clinical and computational perspectives, these findings are significant. For example, the latter finding suggests that there is scope for researching the combination of key process variables used, such as the cement chemistry, the cement delivery system, and the augmentation technique/approach, that would ensure that the final cement domain shape in cement-augmented VBs of patients be oblate spheroid on a consistent and predictable basis.

The purpose of this article is to introduce a novel approach, by using coupled video and radiographic analysis of back surface and spinal curves in the sagittal plane to decrease the ionizing radiation exposure for subjects requiring long-term follow-up of their spinal deformity. This approach is specifically designed for the use in a clinical set-up for the follow-up of subjects with progressive spinal deformities. The subjects are radiographed with nine steel balls embedded in circular markers evenly distributed on the subject's back surface over the spinous processes of C7 to S1. A technique allows to draw the external back profile and the spinal curve. Patient-specific transfer functions are defined moving the back profile to the spinal curve. Sixteen adult volunteers were tested to validate the concepts proposed. For each of them, the values of transfer functions between radiographic back surface profile and corresponding spinal curve have been calculated. Each internal curve is correctly simulated when based upon the back profile. Our research is now focused on the prediction of the internal curve of patients from their back surface profile based on patient-specific transfer functions.

This article describes a fuzzy classifier for the identification of premature ventricular complexes (PVCs) in surface electrocardiograms (ECGs). The classifier uses features extracted from the ECG beat, such as the width of QRS complex and RR interval. The performance of the algorithm is evaluated on the MIT-BIH Arrhythmia Database following the AAMI recommendations. The results of the experiments of the recognition of PVCs have confirmed the reliability and advantage of the proposed approach.

Glenoid failure is one of the major indications for revision in total shoulder arthroplasty. Glenoid components should be carefully designed to improve the reliability of the prostheses, and mechanical testing can be a key tool to compare the performances of different designs. The most relevant guidelines for mechanical testing of glenoid prostheses are included in the ASTM F2028-05 Standard. The Standard refers to glenoid subluxation tests, designed to evaluate the intrinsic stability of the prosthesis system, and to glenoid edge displacement tests, which estimate the risk of micro-motions at the bone-glenoid interface. However, some indications given by the Standard are not mandatory, leaving the possibility to choose some parameters of the testing set-up and procedure. The main goal of this study was to investigate how different testing parameters (i.e. loads, velocities and bone-glenoid conformity) may affect the test results. In order to reach this target an experimental apparatus was developed and mechanical tests were performed on a keeled glenoid. The study showed that the applied load and the bone-glenoid conformity have a significant effect on the tests results, because of bone and glenoid deformation. Contrarily, the testing velocity was not found to be an influencing testing parameter.

In this work, an attempt has been made to correlate the dielectric permittivity of polyacrylamide based tissue mimicking phantoms with their mechanical properties such as breaking stress, breaking strain and Young's modulus. The tissue mimicking phantoms of various concentrations were prepared as per the standard protocol and their permittivity was measured using a precision impedance analyzer. The mechanical properties of the phantoms were measured by conducting tensile tests using a Universal Testing Machine. The measured mechanical properties were correlated with the dielectric permittivity by performing statistical analysis. Results demonstrate that the percentage variation in the mechanical properties correlate well with the percentage variation in the permittivity of the tissue mimicking phantoms. Further, it appears that the changes in the mechanical properties of the phantoms can be estimated by quantifying the changes in their dielectric permittivity. In this paper, the objectives of the study, methodology and significant observations are discussed in detail.

In this paper, a transparent physical head model with air bubbles to simulate the brain cavitation phenomena in head decelerating impact is presented. The transparent skull model was generated based on a real human skull through the turnover formwork technique, and a transparent gel was used to substitute the brain tissue. Air bubbles were created in the gel at the representative sites such as coup site and contrecoup site. After this, the head model was made to free fall from a position and impact on a fixed platform. The decelerating impacting process was recorded by a high-speed video camera and an accelerometer system. Through analyzing the video, the volume change of the air bubbles, namely, the mean pressure change of the air bubbles were calculated and compared. This new method has an advantage in investigating the brain cavitation phenomena using a direct and visual technique. The results showed explicitly and effectively that during the decelerating impact the contrecoup site air bubble was exposed mainly to a negative pressure which value became smaller and smaller in the first half of the impacting cycle and then came near to the normal level in the second half of the cycle; contrarily, the coup site air bubble was exposed mainly to a positive pressure which value became greater and greater in the first half of the impacting cycle and then came near to the normal level in the second half cycle. The probable biomechanics of the cavitation phenomenon is also given in this paper.