Biomedical Engineering: Applications, Basis and Communications

Surface microcoils are utilized in micro magnetic resonance imaging and spectroscopy for the purpose of resolution enhancement and small sample analysis. In this work, modeling and investigation of surface microcoils are conducted using finite element simulations in COMSOL Multiphysics and post-processing. The method is based on MR signal generating by employing the principle of reciprocity to obtain signal sensitivity and signal-to-noise ratio (SNR) in surface microcoils. Filling factor is investigated as an effective coil parameter to show its great effect on sensitivity and SNR where the results confirm that maximum SNR can be achieved with optimum parameters when the filling factor is high enough. Regarding the great interest on MR coil optimization and microcoil array design, the findings can facilitate the optimization and design process by focusing on the most effective parameters to achieve the desired specifications in an accurate and time-saving manner.

Sparse representation is a powerful tool for image processing, including noise removal. It is an effective method for Gaussian noise removal by taking advantage of a fixed and learned dictionary. In this study, the variable distribution of Rician noise is reduced in magnetic resonance (MR) images by sparse representation based on reconstruction error sets. Standard deviation of Gaussian noise is used to find these errors locally. The proposed method represents two formulas for local error calculation using standard deviation of noise. The acquired results from the real and simulated images are comparable, and in some cases, better than the best Rician noise removal method due to the advantages of stability and low sensitivity to the parameters. Additionally, the devised algorithm acts automatically, because the proposed method includes the phase that estimates the noise properties.

Studies have shown that defibrillation threshold for current amplitude of biphasic truncated exponential (BTE) waveform has a hyperbolic strength–duration relationship. Theoretical and experimental results have shown that decreasing the tilt of BTE waveforms decreases the defibrillation threshold. On the other hand, low peak current waveform reduces probability of myocardium damage and burn. Therefore, achieving a waveform with low tilt and low peak current is desired. All DC defibrillators use a capacitor to store and deliver required energy. Because of capacitor discharging nature, the tilt of waveforms is high. In rectilinear biphasic waveform (RBW), which was generated by ZOLL M-series defibrillator, the tilt of the first phase was decreased using an adjustable resistor connected in series with current path. But the defibrillator cannot keep the current constant in the second phase and in the both phases for high transthoracic impedances (TTI) either. In this paper, for solving these problems, a circuit that generates rectangular biphasic waveform is designed. In this circuit, five resistors are used and connected in series. Then an IGBT switch is connected to each resistor in parallel. Also, control of minimum current ripple is applied in order to decide which resistors should be worked in each time. The circuit is simulated in MATLAB/Simulink and a prototype model is constructed. Results demonstrate that the tilt of the waveform is notably reduced to a value less than 10%.

Hearing aid implant is not suitable for little children with congenital aural atresia because their skulls are still growing. Since the critical period of speech and language development is during the first three years of life, the child has to be exposed to verbal stimulation as early as possible. The purpose of this study is to develop an external bone-conduction hearing aid for a newborn child. A headband or spectacle can be used to keep the hearing aid in position. To improve the design of the hearing aid vibrator, finite element analysis was applied to analyze the structure factors that affect the performance of the vibrator. The vibrator and head were simulated as a whole system to acquire more accurate estimation of the spectral response of the bone-conduction hearing aid. The measurement on artificial mastoid shows the vibrator has a wide working range from 200 to 4000 Hz, which covers the most crucial acoustic frequency range for speech recognition. The test of bone conduction hearing aid on adult subjects shows comparative performances with a commercial device. This miniature and low-price bone conduction hearing aid will help the specific group of hearing impaired kids to begin the required early intervention therapy.

One of the medical applications of noninvasive laser-ultrasound is in the diagnosis of eye diseases. In such applications, specific features are detected in the received signals produced by generation and reflection of ultrasonic pulses in the intraocular interfaces. Due to the noisy nature of the process, the desired features are typically faded in the received signal. Therefore, denoising the signal is inevitable. The noise suppression technique, with the combination of wavelet transform and independent component analysis (WICA), is widely used for biomedical signals. However, when signals are not obtained by the multichannel recording systems, independent components (ICs) of the wavelet coefficients are not extracted completely by independent component analysis, and rejecting any extracted signals will cause data loss. This paper develops a new technique using improved version of WICA to eliminate this drawback for laser-ultrasound signals obtained from a single channel recording system. The approach is based on extracting ICs of wavelet detail coefficients of the noisy signal and applying the threshold on the ICs to reduce the noise. The proposed method is evaluated on two real laser-ultrasound signals by artificially adding white Gaussian noise to study the distortion measures of the filter outputs. The results of the study demonstrate superior performance compared with conventional denoising approaches such as WICA, wavelet denoising and median, Wiener and lowpass filters over a wide range of laser-ultrasound signal-to-noise ratios.

Locating the Optic Disc (OD) and Macula Center (MC) is the main step in the automatic extraction of retinal anatomical structures for Diabetic Retinopathy (DR). In this work, a variety of vessel segmentation methods have been adopted for the identification of OD in retinal images. In order to locate OD, different segmentation algorithms like matched filter, spatially weighed Fuzzy C-means and threshold are used to detect the blood vessels from the retinal image. Matching the expected directional pattern of the retinal blood vessels is proposed to locate the OD center. The proposed vessel direction filter is resized and OD center is measured. Macula center (fovea) is located at a constant distance from optic disc. A new method with geometric approach is proposed for macula detection. The proposed methods have been evaluated using a STARE and DRIVE datasets which contains both normal and diseased retina. The proposed methods are successfully adopted for segmentation of blood vessels and location of OD and MC in both normal and abnormal images.

In this paper, rehabilitation tools are proposed and implemented to assist patients with stroke and body dysfunction via auxiliary physical activity. By integrating the entertainment of games and the needs of rehabilitation and utilizing motor assessment scale (MAS) as the building blocks, we propose a game system developed for assessment of stroke rehabilitation by using augmented reality (AR) technology. By means of application of AR Markers and based on related parameters of Wii remotes, various assessment games have been implemented, and vivid pictures can be presented to users via a head-mounted display by seamless combination of real environment and virtual objects. This game system takes various assessment scales into consideration, and each scale is specifically designed and individually integrated to enable the relevant capacity for assessment of motor functions. According to the experimental results, the accuracy rate of the users in successfully following the game steps is 91.2%, and the accuracy rate of the system in assessing the MAS categories is as high as 94.6%, which confirms the feasibility of our proposed and implemented rehabilitation game system.

The biomechanical data derived from the standard tensile testing machines may not be able to show the relative motion of the graft limbs. This paper uses a digital stereo image recording system, synchronized with the standard test machine, to determine the relative motion of a looped tendon graft. Bovine flexor tendon was used to create the looped graft and then the graft was passed through a tunnel in a foam block and fixed with an interference screw. The structure was then mounted in a testing machine. The tendon limbs surfaces were speckled just moments before test, and two cameras synchronized with the test machine were capturing the movements of the speckles. Following a cyclic loading from 50–250 N at 1.0 Hz for 500 cycles, a load-to-failure test was carried out at a rate of 20 mm/min. The load-displacement data and the corresponding images of the graft were used to examine the mechanical properties of the graft structure and the relative motion of the individual graft limbs. There was no significant difference between the mechanical properties of the grafts structure. The average displacement of the grafts structure was 6.95 mm, while the average relative motion between the loop limbs up to the point of the graft failure was 0.3 mm.

Heavy metals greatly influence animal physiology, even at small doses. Among these metals, the copper ion is of great concern due to its effects on humans and wide applications in industry. Compared to atomic absorption spectroscopy and inductively coupled plasma-mass spectrometry, which destroy the samples that are analyzed, optical techniques do not decompose the analyte and have become a popular field of recent research. In this paper, we combined a novel optical detector that did not require sample-labeling, called surface plasmon resonance (SPR), with chitosan to detect copper ions by modifying the functional groups of chitosan through pH modification. Compared to other optical detectors, the SPR system was relatively fast and involved fewer experimental confounding factors. The three-dimensional structure of chitosan was used to obtain lower detection limits. Moreover, modification of the chitosan functional groups resulted in efficient regeneration by controlling the pH. A detection limit of 0.1 μM was obtained (linear range: 0.5–10 μM, R² = 0.976), and the specificity was certified by comparing the copper ion with six other ions. Additionally, we successfully regenerated the SPR chips by modifying the functional groups. In conclusion, the chitosan–SPR system detected copper ions with improved detection limits using a quick and simple regeneration method.

Brain damage pathology can generate an irrelevant motor program leading to abnormal posture. Given this observation, we tested the hypothesis that postural control deficits are present in individuals with postural disorders. A new trunk sway assessment protocol evaluation system using an inertial-based sensing technique combined with visual-biofeedback strategies was developed. The proposed system was used to assess the angular deviation of the center of mass and enhanced balance control in patients with stroke. Twelve participants with hemiplegia were randomly divided into a visual-biofeedback group (experimental) and a without visual-biofeedback group (control), and were asked to stand as still as possible for 30 s. Postural sway data were submitted to conventional quantitative analyses of sway magnitude using a center of mass measurement. Additionally, group means were compared using parametric tests. Parameters in both the anterior-posterior and medio-lateral directions within the stroke patients were compared using paired t-tests. The experimental group showed increased postural control, indicative of reduced postural sway. Decreased complexity in the medio-lateral direction was also observed in the experimental group, suggesting both a reduction in the dynamic range available for postural control, and that their postural corrections were dominated primarily by longer-term scales. Significant interactions between the diagnostic group and visual condition were also observed for both of these measures, suggesting that the control group participants were impaired in their ability to make corrections to their sway pattern when no visual biofeedback was available. Greater sway magnitude and reduced complexity suggest that individuals with hemiplegia have deficits in sensorimotor integration and a reduced range of timescales available within which to make postural corrections.