Biomedical Engineering: Applications, Basis and Communications

Sintered dicalcium pyrophosphate (SDCP) is a synthetic pyrophosphate analog that could be utilized in the treatment for osteoporosis. In this study, an ovariectomized rat model is used to evaluate the systematic toxicity of orally administered SDCP relative to its effects on bone mass. Ovariectomized Wistar rats were treated with experimental medication with different dosing strategies (0.5 mg/kg five days weekly, and 2.5 mg/kg once weekly) for once (acute oral toxicity test) and four weeks (subacute oral toxicity test) followed by recovery period. Clinical signs of toxicity, body weight, and food consumption of rats were recorded. Blood samples were collected for hematological and blood biochemical analyses. Rats were sacrificed for necropsy and major visceral organs were harvested for histological examination after the recovery period. Long bones of four limbs were harvested to evaluate the effects of SDCP on bone mass. Results showed that there was no change in clinical signs, body weight, food consumption, hematology, blood biochemistry, necropsy, and histological examination attributable to the oral administration with SDCP to rats during the dosing period and the recovery period. Analysis of bone ashes revealed that the ovariectomized rats ingested with 0.5 mg/kg SDCP five days weekly continually for four weeks increased bone mineral contents significantly. In the ovariectomized rats ingested with 2.5 mg/kg SDCP once weekly continually for four weeks, the bone mineral contents were increased to normal bone quality. This study indicates that the SDCP can increase bone mass in the ovariectomized rat with no deleterious effects.

We present an additive Poisson data modeling of attenuation map reconstruction from post-injection positron emission tomography transmission scan. The transmission scan data are modeled as a collection of independent Poisson observations which consist of true transmission, cross-contamination emission and random coincidences. The mean values of cross-contamination emission and random data are estimated by using Luk's approximation and Zaers' method, respectively. The unknown attenuation map is also modeled using a Gibbs image prior. Under the paradigm of Bayesian statistics, a pre-conditioned conjugate gradient algorithm is then used to compute a maximum a posteriori estimate of the attenuation map by maximizing over the posterior density. Evaluations are conducted on clinical data collected from a CTI EXACT HR+ scanner. Experimental results have indicated that the reconstructed results of attenuation map by the proposed reconstruction algorithm match well with theoretical values of soft tissue, bone and lung under 511 keV photons.

The gaze tracking system has become an active research field for handicapped persons as well as general people in recent years. The precise mapping method plays an important role in the system. In this paper, a novel infrared gaze tracking system based on nonuniform interpolation is proposed. In this system, the eye images for the computer to analyze are extracted under two infrared light sources and a charge-coupled device camera, and the users do not require wearing any device. First, the integral projection algorithm and canny edge detection are applied to extract the pupil boundary points from the captured eye images, and then the pupil center is computed using an efficient and accurate ellipse-fitting algorithm. Finally, to estimate where the user looks, a novel mapping method based on the nonuniform interpolation algorithm is proposed. In this mapping method, the complicated geometric eyeball model and the nonlinear mapping between the pupil center coordinates and computer monitor screen coordinates do not need to be taken into account. Experimental results show that the proposed mapping method is simple, fast and more accurate. Moreover, our system is the remote eye gaze tracking system. The users do not need to wear any device, which make the users feel more comfortable.

A variety of cell lines are often used to simulate the studies associated with the cell products, genetics, cell–cell interaction, environmental interaction, intracellular flux and intracellular activity. Among these cell lines, the pheochromocytoma (PC12 for short) cell line is the one that is widely applied in in vitro study for investigating the neuronal apoptosis, neurochemistry, and neuronal differentiation. The development of an appropriate cell cultivation platform as well as the real-time image acquisition and analysis system becomes an important issue. The purpose of this paper is to develop a long-term and low-cost incubation system, including microscopic image analysis system for morphological analysis. The proposed incubation system can acquire cell image for analysis during cell cultivation. From the experimental results, the temperature of incubation system is found to be in the range of 37.3 ± 1.3°C, and the lower levels of the relative humidity vary within 89.7 ± 1.8%. The CO₂ concentration is controlled at 5.29 ± 0.71%. The cell number is increased from 1.00 × 10⁵ to 4.25 × 10⁵ cells/ml after 48 h of culture. The cell viability test shows that this developed incubation system works well for PC12 cells cultivation; it can also acquire and segment the cell image during the cell cultivation. Besides, in the image analysis software design, the region-growing and modified blob labeling techniques are also employed to segment the PC12 cell image under varied culture conditions for later morphological and feature quantification analysis.

Knowledge of the control of the body's dynamic stability in patients with knee osteoarthritis (OA) is helpful for the management of these patients and for the evaluation of treatment outcomes. The purpose of the current study was to investigate the dynamic stability of patients with knee OA during level walking using variables describing the motion of the body's center of mass (COM) and its relationship to the center of pressure (COP). Kinematic and kinetic data during level walking were obtained from 10 patients with bilateral knee OA and 10 normal controls using a motion analysis system and two forceplates. Compared to the normal controls, patients with knee OA exhibited normal COM positions and velocities at key instances of gait but with significant changes in COM accelerations. In the sagittal plane, adjustments to the anterioposterior acceleration of the COM throughout the complete gait cycle were needed for better control of the COM during the more challenging latter half of single leg stance. Diminished A/P COM–COP separation was also used to maintain body stability with reduced joint loadings. In the frontal plane, this was achieved by increasing the acceleration of the body's COM towards the stance leg. The more jerky motion of the body's COM observed may be a result of reduced ability associated with knee OA in the control of the motion of the COM. Strengthening of the muscles of the lower extremities, as well as training of the control of the COM through a dynamic balance training program, are equally important for the dynamic stability of patients with knee OA.

Swivel walkers have been useful devices in ambulation for many young paraplegic patients for being advantageous in providing reliable stability, easy handling, and hands-free walking. The placement of the foot-plates on swivel walkers affects the gait efficiency. However, the determination of the foot-plate spacing has been purely empirical and no theoretical work has been attempted before. This study aimed to develop a dynamic model of the swivel walker in the coronal plane to formulate an optimal design problem such that the energy loss due to impact could be computed and minimized within a feasible range of the coronal-plane movement. Children of heights from 0.75 to 1.45 m and weights from 15 to 45 kg fitted with the conventional swivel walkers were simulated. The results indicated that the range of the foot-plate spacing was roughly between 1/4 and 1/6 of the body heights. A regression formula was also derived to estimate foot-plate spacing with respect to the heights and weights of the simulated subjects for clinical applications. We conclude that the theoretical framework not only builds a foundation to determine the foot-plate spacing, but also reveals the dynamic behavior of the swivel walkers in the coronal plane. The results could be applied to the design of other biped locomotion systems.

This study presents a novel mouth-controlled text input (McTin) device that enables users with severe disabilities to access the keyboard and mouse facilities of a standard personal computer via the input of suitable Morse codes processed by sliding window averaging and a fuzzy recognition algorithm. The device offers users the choice of four different modes of operation, namely keyboard-, mouse-, practice-, and remote-control mode. In the keyboard-mode, the user employs a simple mouth-controlled switch to input Morse codes, which the McTin device then translates into the corresponding keyboard character, symbol, or function. In the mouse-mode, the user is able to control the direction of the mouse movement and access the various mouse functions by inputting a maximum of four Morse code elements. The remote-control-mode gives the user the ability to control some of the functions of household appliances such as TV, air conditioner, fan, and lamp. Finally, the practice-mode employs a training environment within which the user may be trained to input Morse codes accurately and quickly via the mouth-controlled switch. Although this study presents the use of a mouth-controlled switch for the input of Morse codes, the form of the input device can be modified to suit the particular requirements of users with different degrees of physical disability. The proposed device has been tested successfully by two users with severe spinal cord injuries to generate text-based articles, send e-mails, draw pictures, and browse the Internet.

Beamformer is one of the main techniques for spatio-temporal neuroelectromagnetic source reconstruction. However, the classical Beamformer is extremely sensitive to strongly coherent sources, thereby encountering difficulty in localizing the highly correlated bilateral auditory cortices in auditory evoked field (AEF) or auditory steady state evoked potential. The multiple constrained minimum-variance Beamformer with coherent source region suppression (Beamformer-CS) can potentially overcome such difficulties. However, when coherent interferer is located close to the edges of the suppression region, Beamformer-CS has localization bias and the closer it is, the larger it will be. Here, we present an improved Beamformer-CS that can localize coherent sources with much less localization bias, especially in the case of the interferer close to the edges of the suppression region. First, based on approximate information about source energy distribution from other neuroimaging techniques, a region encompassing the coherent interfering sources is defined. Then, the dominant eigenvectors of the lead field matrix, weighted using source energy information obtained by other imaging method, for the suppression region is incorporated into Beamformer design as hard null constraints. Such weighting strategy is able to improve the localization performance. Simulation test shows that, compared to Beamformer-CS, the new weighting approach is of much smaller localization bias, sharper peak of the estimated sources, more robust against noise, and less sensitiveness to the number of the eigenvector components for the suppression region, as is also confirmed by real AEF data test.

There have been significant advances in fabrication of high-density microelectrode arrays using silicon micromachining technology in neural signal recording systems. The interface between microelectrodes and chemical environment is of great interest to researchers, working on extracellular stimulation. This interface is quite complex and must be modeled carefully to match experimental results. Computer simulation is a method to increase the knowledge about these arrays and to this end the finite element method (FEM) provides a strong environment for investigation of relative changes of the electrical field extension surrounding an electrode positioned in chemical environment. In this paper FEM simulation environment is used for modeling the metal–chemical interface, which provides helpful information about noise, impedance, and bandwidth for circuit designers to design the front-end electronics of these systems, more efficiently and reliable.

As balance is the foundation for all voluntary motor skills, considerable research has been conducted to evaluate postural control in patients with low back pain (LBP). Although reliability is a population-specific property, to the authors' knowledge, there has been no study to determine the test-retest reliability of the center of pressure (COP) measures in the general population of LBP patients. As many as 11 patients with a history of nonspecific LBP randomly completed postural measurements with three levels of difficulty (rigid surface-eyes open, rigid surface-eyes closed, and foam surface-eyes closed) in two sessions. The COP data were used to calculate standard deviation of amplitude, phase plane portrait, standard deviation of velocity, mean total velocity, and area (95% confidence ellipse). Relative reliability of these measures was assessed using intraclass correlation coefficient (ICC) and absolute reliability using standard error of measurement (SEM), and coefficient of variation (CV). Among different COP parameters, the mean total velocity in all conditions of postural difficulty showed the highest reliability, with the ICC range of 0.73–0.80, SEM range of 0.09–0.32 cm/s, and CV range of 5.7–8.2%. Therefore, the mean total velocity may be an optimal COP parameter to be used for quantification and assessment of balance performance in LBP patients.