Biomedical Engineering: Applications, Basis and Communications

Fibrin sealant and platelet gels are human blood-derived, biodegradable, non toxic, surgical products obtained by mixing a fibrinogen concentrate or a platelet rich plasma with thrombin, respectively. Fibrin sealant is now a well known surgical tool increasingly used to stop or control bleeding, or to provide air and fluid tightness in many surgical situations. Platelet gels are newly developed preparations that are of specific interest because they contain numerous physiological growth factors and cytikines that are released upon the activation of blood platelets by thrombin. These growth factors, including PDGF, TGF-β 1, BMP, and VEGF have been shown to stimulate cell growth and differentiation with special clinical benefits for soft and bony tissue healing and regeneration. Platelet gels allow surgeons to manipulate the cellular environment of surgical sites and to guide tissue regeneration. A specific interest of such products is observed for the induction of osteogenesis and chondrogenesis. Advances in the preparation, clinical use, and safety of these two important classes of blood-derived biomaterials are reviewed.

Numerous disciplines are engaged in studies involving motor control. In this study, we have used a single link system with a pair of muscles that are excited with alpha and gamma signals to achieve an oscillatory movement with variable amplitude and frequency.

The system is highly nonlinear in all its physical and physiological attributes. The major physiological characteristics of this system are simultaneous activation of a pair of nonlinear muscle-like-actuators for control purposes, existence of nonlinear spindle-like sensors and Golgi tendon organ-like sensor, actions of gravity and external loading. Transmission delays are included in the afferent and efferent neural paths to account for a more accurate representation of the reflex loops. The profile of excitation is difficult to predict a priori, hence we have used a reinforcement learning approach to track a desired trajectory.

This paper proposes a reinforcement learning method with an Actor-Critic architecture instead of middle and low level of central nervous system (CNS). The Actor in this structure is a two layer feedforward neural network and the Critic is a model of the cerebellum. The Critic is trained by State-Action-Reward-State-Action (SARSA) method. The Critic will train the Actor by supervisory learning based on previous experiences. The system is implemented on a PC using Matlab^® and Simulink^® Software. To enhance the computational performance a number of C codes were also written.

The effectiveness and the biological plausibility of the present model are demonstrated by several simulations.

The system showed excellent tracking capability and after 280 epochs the RMS error for position and velocity profiles were 0.02, 0.04 radian and radian/sec, respectively.

Motivation: The heartbeat is driven by electric signals generated inside the heart, the cardiac conducting system plays an important role. Although there are pharmacological and electrical methods working on this conducting system, effect of mechanical stimulation has rarely been discussed. Methods: We used waterbed (size 60×40×10 cm) as a media to study the heart rate variability (HRV) affected by beating the bed with weak mechanical force with 0.5-mm-Hg amplitude. The waterbed is specially designed to raise the transmission efficiency for sound wave. Results: Among 7 studies on 5 rats, there were almost no changes in diastolic pressure, systolic pressure and heart rate, but average of CV (coefficient of variance) of 15-minute heart rate sequences increased from the control value 0.0098±0.0023 (mean±SD) to 0.0119±0.0032 (mean±SD) during the stimulation and decreased to 0.0078±0.0020 (mean±SD) in 15 minutes after the stimulation [p values (paired t-test, both compared with the control) < 0.006 and < 0.0007 respectively]. Discussion: Here we show that such a weak mechanical stimulation was sufficient to affect the circulatory system. Since the effect is not directly acting on the conducting system, this small power may influence the arterial system through resonance mechanism.

Traditional arterial tonometry permits noninvasive and continuous recording of the arterial pressure waveform, by applanating a superficial artery supported by a bone. In the paper, we present an arterial tonometer to simultaneously register the blood pressure waveform and the arterial time-varying volume. The tonometer consisted mainly of a chamber filled with a conductive fluid, a flexible diphragm in touch with an artery, and a pressure sensor used to detect the underlying arterial pressure. In addition, four electrodes were in parallel diposed in the chamber, two of them were triggered with a constant-current source, and the voltage difference between the other two inner electrodes was assocated with the amount of change in the arterial volume. The pressure calibration curve performed with a mercury sphygmomanometer showed a fairly linear relationship (r = 0.998) between the tonometer's chamber pressure and the voltage output of the pressure-sensing circuit. The volume calibration was carried out with vessel-like cylinders of various diameters and a linear relationship (r = 0.884) of the change in vessel volume to the voltage output of the volume-sensing circuit was obtained. Clinical testing results revealed that the noninvasive blood pressure measurement with the tonometer was appreciably consistent with the invasive measurement with the catheter-tipped pressure transducer. In summary, the arterial applanation tonometer developed may be used to reliably determine the full arterial blood pressure waveform and the change in the arterial volume, and to make the wall compliance assessment of a superficial artery possible.

Nowadays magnetic resonance imaging (MRI) has been commonly used in many indications. Concurrent development of MRI contrast agents has aided the rapid expansion and increased clinical efficacy. The use of contrast agents can improve lesion detection and characterization. With the contrast enhancement, lesion conspicuity is dramatically increased. Therefore, contrast enhanced MRI could provide more accurate diagnosis and be helpful for further therapy. The routinely used dose of contrast agents suggested by the documents only relies on the body weight of the subject. However, the relationship between the signal enhancement and the dose of contrast agents needs to be further investigated in order to achieve the maximum enhancement from optimal dose of the contrast agents. The aim of this study is to obtain the optimal dose of two contrast agents (Magnivist and Omniscan) for various T1-weighted pulse sequences (SE, SPGR, 2D TOF and 3D TOF) and various coils (body coil, NV array coil and head coil). The optimal dose is defined as achieving the MR images with the highest enhancement. The results show that there are significant differences in optimal dose among various pulse sequences. However, there are no significant differences in optimal dose among various coils and these two contrast agents. The advantage of finding optimal dose is to minimize dose and potential toxicity, and furthermore to decrease the cost of contrast agents. This study was done on a phantom, and it is expected to provide useful information to the contrast enhanced MRI in the routine clinical diagnosis and research in the future.

The Phoenix left ventricular assist device is driven by pneumatic pump outside a human body to provide air flow in-and-out of a pneumatic diaphragm inside the blood chamber. The inflation and deflation of the diaphragm drives the blood flows. At peak systole, blood flows into aorta with a maximum flow rate both from natural ventricle and artificial ventricle. To assess the critical condition, blood flow pattern of the device at peak systole is studied. We apply the finite volume method with ϰ – ε turbulent model to simulate the steady flow at peak systole. Results provide a comprehension of fluid dynamic effect not only the region inside the ventricle but also that in the vicinity of the inflow channel and outflow valves of flow field. The numerical results show that maximum velocities were smaller within the ventricular chamber with bi-leaflet outflow valve than with tilting disk outflow valve. Analysis of the numerical solutions suggests that geometry similar to the bi-leaflet outflow valve results in a better flow dynamics within the ventricle chamber compared to a tilting disk valve.

The object of this paper is to present a set of techniques integrated into two low-cost human computer interfaces. Although the interfaces have many potential applications, one main application is to help the disabled persons to attain or regain some degree of independent communications and control. The first interface is a voice-controlled mouse and the second one is an accelerometer-based mouse.

Biopotential measurements are very important in clinical diagnosis. However, the signal amplitude of biopotenials is very small and there usually exists stray capacitance between the electrode leads (or the human body) and the power lines, biopotential measurements are easily contaminated by 60-Hz (or 50-Hz) power-line interference.

Analog or digital notch filter has been the most popular technique used for power-line interference removal. However, the notch filter performs well only when the power frequency is kept exactly at the stop band of the notch filter. The adaptive filtering technique provides another promising approach, yet there needs another reference channel for interference recording. The price of signal measurement is thus increased.

The authors present a simple LMS-style algorithm for canceling the power-line interference in biopotential measurement. No reference channel is needed for adaptive filtration in this proposed algorithm. Compared with another technique serving for the same purpose, the proposed algorithm can remove practical power-line interference more effectively, and can be a post-acquisition processing remedy for biosignals having corrupted by power-line interference.

Previous studies showed that the relation for product of peak velocity and duration against saccadic amplitude was highly linear correlated. The velocity profile was related as a triangular profile and referred to the saccadic amplitude as an integration of the profile, so that the amplitude is proportional to the product of peak velocity and duration. The saccadic amplitude can be described as a function of peak velocity and duration.

In this study, in addition to the triangular profile, the rational power function was applied to explain the above linear relation. The acceleration and deceleration phases can be described, respectively, with the different shape parameters (n₁ and n₂).

Finally, we described the product of peak velocity and acceleration time relating to the acceleration amplitude, and the product of peak velocity and deceleration time relating to the deceleration amplitude. The results show that the acceleration and deceleration phase parameters could be used to accurately delineate the saccadic characteristics.