Biomedical Engineering: Applications, Basis and Communications

Cartilage injuries may be caused by trauma, biomechanical imbalance, or degenerative changes of joint. Unfortunately, cartilage has limited capability to spontaneous repair once damaged and may lead to progressive damage and degeneration. Cartilage tissue-engineering techniques have emerged as the potential clinical strategies. An ideal tissue-engineering approach to cartilage repair should offer good integration into both the host cartilage and the subchondral bone. Cells, scaffolds, and growth factors make up the tissue engineering triad. One of the major challenges for cartilage tissue engineering is cell source and cell numbers. Due to the limitations of proliferation for mature chondrocytes, current studies have alternated to use stem cells as a potential source. In the recent years, a lot of novel biomaterials has been continuously developed and investigated in various in vitro and in vivo studies for cartilage tissue engineering. Moreover, stimulatory factors such as bioactive molecules have been explored to induce or enhance cartilage formation. Growth factors and other additives could be added into culture media in vitro, transferred into cells, or incorporated into scaffolds for in vivo delivery to promote cellular differentiation and tissue regeneration.

Based on the current development of cartilage tissue engineering, there exist challenges to overcome. How to manipulate the interactions between cells, scaffold, and signals to achieve the moderation of implanted composite differentiate into moderate stem cells to differentiate into hyaline cartilage to perform the optimum physiological and biomechanical functions without negative side effects remains the target to pursue.

In this study, we apply a multichannel integrated system to record and analyze intracortical neural signals from the primary somatosensory cortex of rats. Four neural signals are evoked by without stimulation, by stimulation using a toothbrush, pen shaft, and needle. These signals are processed according to the presented procedures. First, spectral subtraction is used to reduce noise and then the nonlinear energy operator is adopted to detect spikes. This process is the signal preprocessing. Independent component analysis is performed with dynamic dimension increase to extract the features and form a feature vector. Then, k-means is employed to group the feature vector into different clusters. The 100% of signals intercepted without stimulation that we observe are separated into Cluster 1; the 67% evoked signals of stimulation by using a toothbrush are divided into Cluster 2; and the 73% evoked signals of stimulation by using a needle are separated into Cluster 4. Some of the features of evoked signals stimulated using a pen shaft are similar to those stimulated by using a needle or a toothbrush. The monitoring subsystem records synchronously the timing of the external stimuli, the waveform of the evoked potentials, the audio of the neural signals, and the action of an experimental rat using a video recording device. The information is applied to assist us in proving of experimental results. Finally, the presented methods are utilized to extract the features from various evoked potentials and distinguish the stimulants from different sensory signals.

In this study, we investigate multiscale entropy (MSE) as a tool to evaluate the dynamic characteristics of electroencephalogram (EEG) during seizure-free, pre-seizure and seizure state, respectively, in epileptic rats. The results show that MSE method is able to reveal that EEG signals are more complex in seizure-free state than in seizure state, and can successfully distinguish among different seizure states. The classification ability of the MSE measures is tested using the linear discriminant analysis (LDA). Test results confirm that the classification accuracy of MSE method is superior to traditional single-scale entropy method. MSE method has potential in classifying the epileptic EEG signals.

Background. For the available systems, the two paired nail holes at the distal femoral portion were of identical size and shape. However, the higher incidence of the first nail-hole failure was reported at the medial than lateral side. In practice, the nail was initially stabilized by the screw insertion into the first hole from the lateral-to-medial side. If the lateral first hole was adequately strengthened, the larger nail-hole diameter could ease to insert the screws into the lateral hole.

Methods. The finite-element method was used to investigate the effect of the configuration of the lateral first hole on the screw insertion and stress distribution of the distal nailing system. The distal nail-hole thickness was increased and its edge was intentionally chamfered to increase its effectively projected area onto the sagittal plane. There were eight variations of the nail-hole configuration in the parametric analyses.

Findings. The deflected nail diagonally contacts the screws at the medial first and lateral second nail-screw sites. The medial first hole was the most stressed and the stress of the medial second hole was the least. The increase in the nail-hole thickness significantly reduces the concentrated stresses of all four holes, thus allowing the lateral first nail-hole diameter to be increased without the strength loss at that site. The enlargement and chamfer of the lateral first hole significantly increase the effective nail-hole projected area and potentially facilitate the screw insertion. Comparatively, the size and shape re-design of the lateral first hole induced the minor increase in stress values of the other holes and screws.

Interpretation. In nature, the load-transferring mechanism between the distal nail-screw interfaces was the point-contact problem. If the wall-thickness, diameter, and chamfer of the lateral first hole were well-controlled, this re-design decreases the stress at the medial first distal hole where most failures occur and renders the overall system mechanically safer and more surgically effective.

Noninvasive surgery of the liver tumors has been carried out by using the high-intensity focused ultrasound (HIFU). However, the liver tumor can be moved by the human respirations and heartbeats, which may cause the ablation and damage of normal tissues during the sonications of HIFU. The purpose of this study was to design and fabricate a cylindrical HIFU phased array transducer for treating the moving liver tumor efficiently. The total number of the element was 512 but only 256 channels were required since the elements along the elevation direction were connected in pairs with respect to the central line of the array. Field II software was used to simulate the acoustic field, and a formula for predicting the spatial averaged intensity at focus was developed based on the practical factors. The results of the simulations showed that the cylindrical HIFU phased array in water had a dynamic focusing range from 145 to 175 mm in the depth direction and a steering range from -15 to 15 mm in azimuthal direction with respect to the center of the array. After the dissipation of cables and the attenuation of various media, the designed array could still generate the intensity at focus up to 1095 W/cm² when the input electrical power was approximately 410 W. The prototype of the array was fabricated and the preliminary test was completed. The testing results showed that each element of the array prototype can work well.

Finger's action has been controlled by both intrinsic and extrinsic hand muscles. Characterizing the finger action with the activations of hand muscles could be useful for evaluating the neuromuscular control strategy of finger's motor functions. This study is designed to explore the correlation of isometric fingertip force production and frequency-domain features of surface electromyography (sEMG) recorded on extrinsic hand muscles. To this end, 13 subjects (five male and eight female university students) have been recruited to conduct a target force-tracking task. Each subject is required to produce a certain level of force with either the index or middle fingertip to match the pseudo-random ordered target force level (4N, 6N, or 8N) as accurate as possible. During the finger force production process, the sEMG signals are recorded on two extrinsic hand muscles: flex digitorum superficials (FDS) and extensor digitorum (ED). For each sEMG trail, the power spectrum is estimated with the autoregressive (AR) model and from which the maximum power is obtained. Our experimental results reveal three findings: (1) the maximum power increases with the force level regardless of the force producing finger (i.e. index or middle) and the extrinsic hand muscle (i.e. FDS or ED). (2) The sEMG maximum power of index finger is significantly lower than that of the middle finger under the same force level and extrinsic hand muscle. (3) No significant difference can be found between the maximum powers of FDS and ED. The results indicate that the activations of the extrinsic muscles are affected by both the force level and the force producing finger. Based on our findings, the sEMG maximum power of the extrinsic hand muscles could be used as a key parameter to describe the finger's actions.

A doctor often has to independently make decisions for the therapy or treatment of patients, such as during clinical emergency calls, some of the most challenging tasks for a doctor. Only if a doctor has highly sophisticated "professional knowledge" and rich "diagnosis and treatment experiences", can he or she be competent for these tasks. Therefore, the inheritance of experience from clinical emergency calls is an important connection in the formative education of doctors. The most traditional formative education of doctors is to have students simulate the diagnosis and treatment modes of their teachers, or carry handbooks containing clinical summaries to perform a diagnosis with them as guidelines. However, this temporary approach of finding answers in books is not only time-consuming, but also detrimental to the confidence of the patients in their doctors. Our research involves the aforementioned clinical practices: clinical emergency calls and doctor formative education. We use ophthalmology as an example and utilize the back-propagation algorithm of the artificial neural networks, to construct an approximate decision model of medical record to guide clinical diagnosis. The doctor can input information such as chief complaint, minor complaints, diagnosis, etc. into the decision model. Correct ophthalmologic approximation medical records are created by referencing diagnosis and treatment to improve the quality of medical treatment and medical care.

Wrestling is one of the oldest and most popular competitive sports in the world, however, knowledge of the biomechanics of wrestling is not well established and the biomechanical risk factors of injuries unclear. The purpose of this study was to investigate the joint kinematics of the lower limbs and the center of pressure (COP) movements in Greco-Roman style (GR) and free style (FS) wrestlers during tackle defense. Eighteen male college wrestlers participated in the current study: 10 majored in GR (height: 171.1 ± 8.0 cm; weight: 73.9 ± 11.5, kg) and 8 in FS (height: 169.0 ± 5.2 cm; weight: 71.8 ± 11.4 kg). The wrestlers received tackle attacks from three different directions while their kinematic data measured by a 3D motion capture system and ground reaction forces from two AMTI forceplates. The wrestlers who majored in GR style tended to resist tackle attacks longer than the FS group. Compared to the GR group, the FS wrestlers tended to have greater A/P excursions of the COP with significant greater knee flexion. This flexed knee strategy may be related to the rule of the game and the training the FS wrestlers received. Significantly increased joint angles in the transverse and frontal planes at the knee and ankle found in the current study may be related to the risk of knee and ankle injuries commonly observed in wrestlers. Strengthening of the muscles of the lower extremity may be helpful for reducing these injuries during competitions.

Skin marker-based stereophotogrammetry has been widely used in the in vivo, noninvasive measurement of three-dimensional (3D) joint kinematics in many clinical applications. However, the measured poses of body segments are subject to errors called soft tissue artifacts (STA). No study has reported the unrestricted STA of markers on the thigh and shank in normal subjects during functional activities. The purpose of this study was to assess the 3D movement of skin markers relative to the underlying bones in normal subjects during functional activities using a noninvasive method based on the integration of 3D fluoroscopy and stereophotogrammetry. Generally, thigh markers had greater STA than shank ones and the STA of the markers were in nonlinear relationships with knee flexion angles. The STA of a marker also appeared to vary among subjects and were affected by activities. This suggests that correction of STA in human motion analysis may have to consider the multijoint nature of functional activities such as using a global compensation approach with individual anthropometric data. The results of the current study may be helpful for establishing guidelines of marker location selection and for developing STA compensation methods in human motion analysis.