Key Engineering Materials Vols. 326-328

Abstract: AFO is a device, which is usually recommended for hemiplegics to help their pathologic gait. To date, no good engineering guidance is available. We analyze mechanical characteristics of AFO and evaluate structural stability effect of thickness of ankle foot orthosis (AFO). The study is to provide a guidance to make a functional AFO. Basic material characteristics such as Young’s modulus and Possion’s ratio were measured through material tests. Finite element models were made and analyzed based on various shapes and gait analysis. Young’s modulus of polypropylene is 1.15 GPa and Possion’s ratio is 0.35. Rigidity of AFO is more affected by the ankle width than the thickness of ankle area. The strain calculated by finite element analysis (FEA) in the neck area is twice as much as experimental results but the both of their trend show similar pattern. AFO was studied through its structural and functional analysis. Experimental structural analysis and FEA were made and compared.

Abstract: In this study, we assessed spasticity objectively and quantitatively using the pendulum foot drop test. Twenty-eight patients with spasticity and ten healthy subjects participated in the study. A newly designed table for the motion analysis system using infrared cameras and a foot release mechanism were used. Electromyograph (EMG) was recorded from eight muscles of the lower limb during a foot drop maneuver. The study investigators suggest ‘modified relaxation index’ as a good representative parameter for describing spasticity. This parameter is based on quantitative measurement rather than investigator discretion, as in the modified Ashworth scale (MAS).

Abstract: Biological flows, especially blood flow, have attracted a great deal of attention from fluid engineering and hemodynamic investigation fields with advances in bio-technology. The flow of blood carries dissolved gases, nutrients, hormones, and metabolic waste through the circulatory system in the human body. In the present study, the characteristics of blood flow inside a microchannel are investigated by using a micro-particle image velocimetry (micro-PIV) and an optical image processing technique. The motion of red blood cells (RBCs) was visualized with a high-speed CCD camera. The microchannel is made of polydimethylsiloxane (PDMS) material and a slide-glass is attached to the top. The thickness of the margin cell depletion layer is calculated from an acquired raw image through the image processing method, with variations in microchannel width.

Abstract: We recognized EMG signal patterns of lower limb muscles by using neural networks and performed feature evaluation during the recovery of postural balance of human body. Surface electrodes were attached to lower limb and EMG signals were collected during the balance recovery process from a perturbation without permitting compensatory stepping. A waist pulling system was used to apply transient perturbations in five horizontal directions. The EMG signals of fifty repetitions of five motions were analyzed for ten subjects. Twenty features were extracted from EMG signals of one event. Feature evaluation was also performed by using DB (Davies-Bouldin) index. By using neural networks, EMG signals were classified into five categories, such as forward perturbation, backward perturbation, lateral perturbation and two oblique perturbations. As results, motions were recognized with mean success rates of 75 percent. With the neural networks classifier of this study, the EMG patterns of lower limb muscles during the recovery of postural balance can be classified with high accuracy of recognition.

Abstract: We assessed the effects of muscle forces on ankle joint kinetics during postural balance control of human boy. Nine male subjects (mean age of 25.8 yrs) participated in the experiment. An ankle joint model assumed ball and socket joint was used, which was capable of three dimensional rotations. A six-camera VICON system was used for motion analysis. Waist pulling system and force platform were adopted for forward sway and GRF (ground reaction force) measurement. We used linear optimization programs to calculate the variation of muscle forces and angular displacements of shank and foot segments. With the experimental data and linear programs, we could calculate joint reaction forces, and bone-on-bone forces. The results presented in this study give us the insights to understand the roles of lower limb muscles during postural balance control and ankle injury mechanism.

Abstract: In this paper we present an analysis of medical images based on robot kinematics. One of the most important problems in robot-assisted surgeries is associated with the medical image registration of surgical tools and anatomical targets. The fundamental problems of contemporary frame-based image registration are that the registration fails in case of incomplete data in the image and the registration algorithm depends on the shape, assembly, and number of fiducials. To solve the registration problem in the situation where a cylindrical end-effector of surgical robots operates inside the patient’s body, we developed a numerical method by applying robot kinematics knowledge to cross-sectional medical images. Our method includes a 6-D registration algorithm and a cylindrical frame with four helix and one straight line fiducials. The numerical algorithm requires only a single cross-sectional image and are robust to noise and missing data, and are algorithmically invariant to the actual shape, number, and assembly of fiducials. The algorithm and frame are introduced in this paper, and simulation results are described to show the adequate accuracy and resistance to noise.

Abstract: A novel micro cell incubator is described in this paper. pH of animal cell culture media must be tightly controlled, and this is accomplished by supplying defined concentration of carbon dioxide. In order to fabricate a small self-contained carbon dioxide supply unit, we adopted chemical production of carbon dioxide rather than compressed storage of the gas which requires huge tank. Carbon dioxide can be chemically produced by pyrolysis of sodium bicarbonate. The produced gas passes through a thin polymer membrane which is known to admit diffusion of gases. Liquid media separated from gas area by polymer membrane can uptake the gas, then. This micro cell incubator would be a suitable model for the development of portable and arrayed cell chips.

Abstract: In this study, we investigated the effect of the use of alginate sponge as a chondrocyte-3D scaffold for the construction of a cartilage graft. Alginate sponge was made by 5% alginic acid which was crosslinked by CaCl2. Chondrocytes were obtained from a nasal septum after the operation and cultured in 3D alginate sponge. For analysis of cell differentiation, we have checked aggrecan, collagen type I and II using RT-PCR and performed the histological and scanning electron microscopy analysis. Our experiments showed that alginate sponge of 5% promoted sufficient chondrocyte proliferation and differentiation, resulting in the formation of a specific cartilage matrix. The sponge presents new perspectives with respect to in vitro production of "artificial" cartilage. We conclude that the alginate sponges have potential as a scaffold for cartilage tissue engineering.

Abstract: We anticipate the development of new real time biological active point (BAP) systems based on skin impedance, since this measurement method has the superior characteristics of noninvasiveness and easy operation. In this paper, we report on the three electrode measure method that has the advantage of measuring the impedance of the BAPs under the skin. This system easily measured the potential difference between the measurement electrodes and reference electrodes. The BAPs have lower impedance at all frequencies and their reactance is much smaller than that of the surrounding skin. The characteristic frequencies of BAPs are about 20-30HZ higher than that of the surrounding skin. This technology analyzed accurately and objectively the reactance and characteristic frequency of BAPs.

Abstract: Diffusion tensor imaging (DTI) provides quantitative information in the magnetic resonance imaging on the diffusion anisotropy about the integrity of white matter tracts. The aim of this study was to measure diffusion anisotropy and to correlate with upper-limb motor recovery in four chronic hemiparetic patients with thalamic hemorrhage. Fractional anisotropy (FA) was measured in the posterior limb of internal capsules (IC) in the affected side and in the corresponding contralateral normal side before and after 6 week motor training. The correlation between motor recovery of the affected hand and the ratio of FAs of the affected side and the contralateral normal side were investigated. Both FA ratio and motor function significantly increased after the training. A significant correlation was found between motor recovery and FA in the posterior limb of IC. The degree of impairment in diffusion anisotropy of hemiparetic patients might be helpful in prognosis of the motor function.