Biomedical Engineering: Applications, Basis and Communications

Arterial stiffness, resulting in loss of the elastic properties of arteries walls, is an indicator of cardiovascular risk, though the presence of disease is not clinically evident. Augmentation index is an important biomarker of arterial stiffness by which the cardiac risk of the patient can be diagnosed. The current paper outlines the non-invasive assessment of arterial stiffness by analyzing the morphology or contour of PhotoPlethysmoGraph (PPG) signal. PPG pulse was optically acquired with the developed photometric measurement device and the desired features were extracted to determine PPG augmentation Index (PAI) through advanced signal processing implemented in MATLAB. PAI was quantified by the fourth derivative of the signal by enhancing the location of inflection point (augmentation point) after conditioning the signal by efficient pre-processing and filtering techniques. The results reveal that the statistical distribution of PAI for healthy subjects presents a very low value and a very tight distribution. On the contrary, patients have a higher value of PAI and a wide asymmetrical shape of distribution. This work also establishes the usefulness of PPG contour analysis in the investigation of changes in the elastic properties of the vascular system. In conclusion, PAI has revealed to be a non-invasive indicator for arterial stiffness assessments.

This study evaluates the properties of Tramadol-HCl-loaded polyoxalate (TH-loaded POX) microspheres prepared by oil-in-oil (O₁/O₂) emulsion solvent evaporation method, specifically designed for sustained drug release. Morphology and physicochemical characteristics of the as-fabricated were studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) and Fourier transform infrared (FTIR) spectroscopy, while the encapsulation efficiency and release profile of drug (Tramadol-HCl, TH) from POX microspheres were assessed by high-performance liquid chromatography (HPLC). The influence of reaction temperature, stirring speed, initial drug ratio, molecular weight (M_w) and concentration of polyoxalate (POX) on the fabrication of TH-loaded POX microspheres were investigated. Results showed that the characteristics of the microspheres and drug-loaded content can be optimized by adjusting the parameters of preparation conditions. Also, the degradation behavior of TH-loaded POX microspheres was evaluated from in vitro test for 2 weeks. Overall, the results showed that POX microsphere can be one of the promising polymers for controlled injection release formulation with site-specific drug release capabilities.

Rehabilitation of lower limbs with high-level amputation (Trans-femoral Cut) requires an alternative method of inverse and forward dynamics to be employed. Inverse and forward dynamics are capable of solving the problem of redundancy of muscles in human lower limbs. Furthermore, inverse and forward dynamics can be used for estimating joints moments, predicting body segment kinematics, and estimating the distribution of forces between the agonist/antagonist muscle group with reasonable accuracy [Riener R, Lünenburger L, Colombo G, Human-Centered robotics applied to gait training and assessment robert, J Rehabil Res Dev43:679, 2006; Keller T, Perry JC, Rehabilitation robotics for outpatient clinical and domestic use, WC IFMBE Proc25:291, 2009; Crespo LM, Reinkensmeyer DJ, Review of control strategies for robotic movement training after neurologic injury, J Neuroeng Rehabil6:20, 2009; Hillman MI, Rehabilitation robotics from past to present — A historical prespective, Adv Rehabil Robotics, Lect Notes Contr Inf306:25, 2004.]. However, the application of these methods, in rehabilitation, is still limited due to their dependence on multiple input data that cannot be measured using conventional measurement tools. This study is aimed at verifying and validating new models which are capable of predicting body segment kinematics accurately using features obtained from electromyography (EMG) and adaptive neuro fuzzy inference system (ANFIS). These features are used to model a set of (input\output) dynamic data. EMG signals obtained from full gait cycle trials of a subject are used to calculate joint moments. Kinematics of the body segments are obtained by applying Euler numerical integration. The relative percentage root mean square (RMS) error between predicted kinematics from ANFIS and measured values for hip, knee, and ankle were 2.23%, 0.98%, and 0.69%, respectively. However, the achieved minimal reasonable accuracy for minimum number of measured inputs depends on the characteristics of the gait parameters such as cyclic nature and delayed symmetric activities between right and left leg about mid sagittal plane. Results of the combined model show that higher prediction accuracy of the gait cycle is achieved and so rehabilitation of lower limbs is feasible.

In recent years, multi-scale transform application in image processing especially for magnetic resonance (MR) images has been raised. Wavelet transform is introduced as a useful tool in image processing and it is capable of effectively removing noise from magnetic resonance images. The main problem with wavelet transform is that it is not able to distinguish one dimensional (1D) or higher dimentional discontinuities in images. In other words, since the wavelet transform is two dimensional (2D), it is considered as a separable transform, it is solely able to identify pointwise discontinuity in images. A proposed solution for this issue is an inseparable transform which is named curvelet. Time frequency transform based noise elimination methods, usually rely on thresholding. There are two important factors involved in thresholding: (1) a method to determine the threshold limit, (2) the implementation of the threshold. In curvelet method, by setting a hard threshold at low levels of noise the obtained similarity index is 0.9254. The proposed method for noise elimination and edge detection in this paper is applying curvelet transform in combination with wavelet transform, which on average leads to 10% improvement compared with wavelet method. The results show the efficiency of this method in different parts of image processing on simulated and actual MR images.

The incidence of brain diseases, such as dementia, Parkinson's disease and motor nerve disorder, has increased since 1980s. According to a survey conducted on the incidence in England, US, Japan, Germany and Spain, the dementia death rate, including Alzheimer's disease, had increased by three times for men. The death rate from brain disease, such as Parkinson's disease and motor nerve disorder, has increased by 50% for both men and women. Although this increase can be assumed to be caused by changes in DNA when observing from a genetic perspective, it would take hundreds of years to confirm this. Therefore, environmental factors are regarded as the actual cause. In this situation of a rapidly increasing aging population, the prevention of senile and brain diseases is considered the most important measure because treatment is difficult and the after-effects are severe. A cerebrovascular ultrasonogram, which can frequently allow a self-inspection of the blood vessels for the early detection of the risk factors for disease, is actualized to model with a characteristic test and has shown performance. Supplementation of the system can facilitate an application in the measurement of brain disorder patients with other diseases in the future. This study examined the atypical characteristics through the production of a prototype.

In recent years, ventricular assist devices (VAD) have received a worldwide admissibility and have become the unrivalled tools for replacing a failed heart. Most of the newer generations of these devices, including second and third generations, are designed to produce non-pulsatile flow at constant rotational speed. Here, we have proposed the design of a VAD, which although is an axial flow type, is able to produce pulsatile flow; and this has come through by changing the rotational speed of the impeller of the pump. This pump, which has an output analogous to cardiac output, is able to produce a flow rate of approximately 6 L per minute. Designing of this pump is based on turbomachinery theories and applying computational fluid dynamics (CFD) methods. The proposed pattern of the changes of rotational speed is trapezoidal and consists of four phases. Studies of the shear stresses imposed on the blood within the pump have shown that there has been an acceptable margin of safety for this pump in terms of blood injuries such as hemolysis and thrombosis.

Electroencephalogram (EEG) is a record of ongoing electrical signal to represent the human brain activity. It has great potential for the diagnosis to treatment of mental disorder and brain diseases such as epileptic seizure. Features extraction and classification is a crucial task to detect the stage of ictal (i.e. seizure period) and interictal (i.e. period between seizures) EEG signals for the treatment and precaution of the patient. However, existing seizure and non-seizure feature extraction techniques are not good enough for the classification of ictal and interictal EEG signals considering their non-abrupt phenomena and inconsistency in different brain locations. In this paper, we present new approaches for feature extraction using high-frequency components from discrete cosine transformation (DCT) and intrinsic mode function (IMF) extracted from empirical mode decomposition (EMD). These features are then used as an input to least square-support vector machine (LV-SVM) to classify ictal and interictal EEG signals. Experimental results show that the proposed methods outperform the existing state-of-the-art method for better classification in terms of sensitivity, specificity, and accuracy with greater consistence of ictal and interictal period of epilepsy for benchmark dataset from different brain locations.

Calcium phosphate ceramics, of a similar composition to that of mineral bone, and which possess the properties of bioactivity and osteoconductivity, have been widely used as substitutes for bone graft in orthopedic, plastic and craniofacial surgeries. A synthetic β-tricalcium phosphate, Osteocera™, a recently developed bone graft substitute, has been used in this study. To evaluate the affinity and efficacy of Osteocera™ as bone defect implant, we used a New Zealand white rabbit femur defect model to test the osteoconductivity of this new bone substitute. Alternative commercially available bone substitutes, Triosite^® and ProOsteon500, were used as the control materials. These three bone substitutes show good biocompatibility, and no abnormal inflammation either infection was seen at the implantation sites. In the histological and histomorphometric images, newly formed bone grew into the peripheral pores in the bone substitutes. After six months implantation, the volume of bone formation was found to be 20.5 ± 5.2%, 29.8 ± 6.5% and 75.5 ± 4.9% of the potential total cavity offered by ProOsteon500, Triosite^® and Osteocera™, respectively. The newly formed bone area within the femur defect section for Osteocera™ was significantly larger than ProOsteon500 and Triosite^®. We concluded that Osteocera™ shows better bioresorbability, biocompatibility and osteoconductivity in the rabbit femur defect model.

Conventional spirometry gives information on the overall ventilation of a person's lung; it cannot detect localized disorders in ventilation as occurring in pulmonary edema, pneumonia, tumor, TB, etc. Here we propose a new technique involving the recently developed focused impedance method (FIM) in combination with conventional spirometry to detect localized lung ventilation disorders. Electrical impedance of lung tissue changes as a function of air content and FIM provides a measurement of localized electrical impedance with sensitivity down to reasonable depths inside the body using a few surface electrodes; here we used a six-electrode version. At least four quadrants of the lungs in the frontal plane can be separately measured using a hand-held probe with spring backed skin surface electrodes. Firstly, spatial sensitivity distribution of the six-electrode FIM was obtained using finite element simulation which verified the focusing effect and its depth sensitivity. Percent change in impedance between maximum inspiration and expiration were measured at four quadrants of the chest of a healthy male subject giving four different values; that at the lower right quadrant was found to be the maximum, as also expected based on anatomy. Changes in impedance at this quadrant of the same subject were found to vary proportionately with exhaled air volumes, measured using a bellows-type spirometer. Similar FIM measurements at lower right lung of seven healthy subjects were found to be almost proportional (R² = 0.7) to the total exhaled air volumes (vital capacity). This was the basis of the new technique. For a healthy individual, the ratio of the local impedance change to vital capacity (VC) will fall within a certain range for each of the four lung quadrants. A lower value at any quadrant would indicate disorder within that quadrant, while a larger value would indicate disorder in a region outside the particular quadrant. The FIM electrode probe can then be moved to take measurements at the other quadrants to locate the region of disorder. This preliminary study indicates that FIM in combination with conventional spirometry could be used to detect localized ventilation defects.

Many unwanted traumas occur in daily life, the result of which may be intertrochanteric fractures in the musculoskeletal system. An intertrochanteric femoral fracture is a serious trauma which can lead to pneumonia, pulmonary embolism or death. Therefore, accurate and stable fixation of these fractures is necessary. Schanz screws with a pertrochanteric fixator body are used for the stabilization of intertrochanteric fractures. The stability of fractures created by external fixators is dependent on the frame and bone interaction. The distance between the fixator body and the bone, called "sidebar-bone spacing", is one of the most important aspects of fracture stability. The primary objective in the treatment of these fractures is to maintain the stability of the fracture in the reduction position to allow early mobilization. In this study, an intertrochanteric femoral fracture was fixed with a pertrochanteric fixator, then the effect of sidebar-bone spacing on the fracture line under axial loading was analyzed using AnsysWorkbench software. Stress and strain values on the fracture line and schanz screws were calculated to understand this effect according to the von-Mises criteria. The sidebar-bone spacing was selected as 8, 6 and 4 cm. The von-Mises stress value on the fracture line decreased as the distance between the fixator body and the bone decreased, although strain values increased. In conclusion, decreasing the sidebar-bone spacing in the pertrochanteric fixator used on hip fractures provides stronger stabilization, and demonstrates safer axial loading.