Biomedical Engineering: Applications, Basis and Communications

Positron emission tomography (PET) can reveal subtle metabolic process, which is an important modality for diagnosis. However, spatial resolution of PET images is not as good as computed tomography (CT) or magnetic resonance imaging (MRI), which can show precise anatomical details. Our study is to improve image quality of PET using better reconstruction methods. In this paper, we use a new and efficient method to incorporate the correlated structural information obtained from MRI. A mean estimate smoothing the maximum likelihood estimate (MLE) locally within each region of interest is derived according to the boundaries provided by the structural information. Since the boundaries may not be correct, a penalized MLE using the mean estimate is sought. The resulting reconstruction is called a cross-reference maximum likelihood estimate (CRMLE). The CRMLE is obtained through a modified expectation maximization (EM) algorithm, which is shown to be computationally efficient by our phantom and clinical studies.

The study of the biological effect of ultrasound on tissue has become an important branch of biophysical ultrasonics. Among the important biological effects, which have been discovered, are chromosomal anomalies, cell death, destruction of cellular structures. Although heating may be important in some results, nonthermal mechanics, such as cavitation, are often suggested as being responsible for the observed effects.

In this paper, the biological subject of this study is the red blood cells (RBC); the relationship between the threshold lesion of RBC and frequency of ultrasound was studied. It has been concerned that a suitable frequency value of ultrasound was selected, capable of driving the bubbles to an interesting reaction. The effective mass of the bubble.for the oscillating system is due to the motion of the surrounding medium. For the purposes, by using the approximate expressions for the effective stiffness and mass of a gas body, one can determine the resonance frequency of the gas body. In the closed system, three types of frequencies were employed with different pressure. The cell death threshold varies with the ultrasonic frequency of exposure, the minimum at about 10 MHz. This report is intended to provide a useful way for the study of the biological effect of ultrasound at medically relevant frequencies.

Collagen is the most abundant natural protein found in living systems. While there is a whole family of different collagen types, each differing in sequence, the properties that make this protein so attractive as the building blocks for medical devices, are reflected largely by the unique fibrillar structure of the molecule, as well as defined functional regions that interact with the surrounding cells and other matrix components. As a commercial medical product, collagen can be part of the natural tissue used in the device, or it can be fabricated as a reconstituted product from animal or recombinant sources. Both types of uses have distinct properties that convey advantages and disadvantages to the end product. This review examines the chemistry and biology of collagen and describes some well-documented examples of collagen-based medical devices produced in one or other of these formats.

Slips and falls often occur in the industrial environments. They are not only caused by environmental hazards but also by some biomechanical factors related to deficient ability of postural control to arrest impending falls. The purpose of this study is to simulate the slip condition in human walking and to find out the possible related factors of biomechanics.

Eleven male and 9 female recruited were healthful without any musculoskeletal and neurological impairments. In order to provide different disturbance level, three lean angles of tilting boards were designed as 10, 20, 30 degrees with respect to horizontal plane. Subjects wore a safety harness, stood on the tilting board and were released without awareness. A forceplate applied a soap patch was in front of the tilting board to serve the slippery perturbation and to measure the fool/floor reactions. Movements of body segments were measured using the motion analysis system.

The results were shown that lean angle had a significant effect to all parameters except step length, response time, maximum ankle forward velocity, hip forward velocity, and ankle flex angle. The gender significantly affected on the step length, response time, maximum ankle forward velocity, and knee forward velocity. Larger lean angle made subjects to take a more rapid step. In order to absorb the shock in foot strike, subjects flexed more their knee and increased the foot landing angle in larger lean angle. Male tended to adopt the long step-length strategy to respond to the slippery perturbation and female tended to use the short step-length strategy instead. The results of maximum ankle forward velocity suggested that short step-length strategy could be belter to reduce the foot slip than long step-length strategy.

This experiment investigated the role of the lumbar region in a simple load-holding situation for three asymmetric (0, 45 and 90 deg) platform perturbations for 18 normal, college age males. The platform perturbations included horizontal translation and rotation in addition to stable condition. The weight was 20% of the subjects' body weight. The Balance System (Chattecx Co.) was used to monitor balance performance while the Lumbar Motion Monitor was used to quantify low-back kinematics. The platform perturbation significantly affected both the lumbar motion parameters and the dispersion, an index of postural sway. The asymmetry of direction of perturbation also significantly affected both the postural sway and the lumbar motion involvement. Given the large mass of the spine, corrective/reactive fast movements to maintain the balance due to the unexpected perturbation to the base of support may lead to impulsive loading of the spine which is associated with the low back injuries. The study of postural stability, whilst an additional manual material handling task is being performed presents a more realistic and functional test than the traditional protocols used presently in Balance Clinics. This type of functional dual tasking is a rich paradigm that requires more research investigations.

Ultrasonic cavitation has found potential usages in medical applications, and we are developing a new drug delivery control system based on liposome and cavitation technology. In order to reduce the side effects of drugs and increase the efficacy of drugs, we combine the advantage of the usage of liposome and ultrasonic cavitation to attain the system. In this system, imaging unit and power unit are essential elements. There are many parameters which need to be controlled. By this drug delivery system, we are to verify its safety and availability. In this paper, we describe how this drug delivery system by ultrasonic cavitation to be designed and evaluated.