Tadashi Takemae

A Simulation Study of Intracranial Pressure Increment Using an Electrical Circuit Model of Cerebral Circulation

An electrical circuit model of the cerebral circulation is presented. Changes of pulsatile waves of the intracranial pressure (ICP) and the cerebral blood volume (CBV) with ICP increment were investigated by simulation of the cerebral blood flow using this model. The simulation is performed by a small signal approximation using the pulsatile component. The results obtained are able to explain the phenomenon of changes in pulsatile wave of ICP with ICP increment. With regard to the CBV, the modeling results are useful for application to rheoencephalography (REG) using electrical impedance method for noninvasive ICP monitoring.

New tetrapolar circuit method using magnetic field for measurement of local impedance change in biological substances

A tetrapolar circuit and method using a magnetic field is proposed for measuring the local electric impedance change in living tissue. On the basis of this method, the authors designed an apparatus that can detect impedance changes in two closely situated parts of living tissue, simultaneously and independently. Using this apparatus, they showed the effectiveness of the proposed method by an in vitro experiment and by an in vivo measurement of pulsatile waveforms in the forearm arteries. The detection sensitivity for a local impedance change was confirmed to be higher than that of the conventional tetrapolar method. Pulsatile impedance waveforms measured in the radial and the ulnar parts of the forearm were consistent with those estimated from the anatomical structure.<<ETX>>

The high zero-flow pressure phenomenon in coronary circulation: a simulation study.

A dynamic simulation was performed in order to study the high zero-flow pressure phenomenon by using an electronic model of the coronary vessel. The objective of this study was to establish a relationship between the diastolic arterial pressure and diastolic arterial flow. The simulated study showed that this relationship is approximately linear with a zero flow pressure intercept of approximately 40 mmHg. This result is consistent with the results obtained in animal experimentation conducted by others.

An electronic circuit model of nerve axon for signal transmission

An electronic circuit model of signal propagation in the nerve axon that is based on the neuristor proposed by H.D. Crane (1960) is described. This circuit is a cascade of identical active network segments suitable for integration. The active line has characteristics such as threshold, a refractory period, saltatory propagation, and bidirectional propagation. These properties are similar to those of signal transmission along a nerve axon. There two modes of interconnection of the active line: T and S junctions. Particularly with the S junction, it is possible to materialize bidirectional junctions, one of which has the function of presynaptic inhibition. This model would be useful as an element of digital systems and as an artificial nerve axon.

Study of the endo-epi flow ratio by using an electronic circuit model of the coronary vessel

An electronic circuit model of the coronary vessel using field effect transistor (FET) was used to perform dynamic simulation of the left coronary circulation and to study the changes in the endo-epi flow ratio of the myocardium in order to demonstrate the vulnerability of the subendocardial layer of the intramyocardium to various coronary arterial diseases and the way the coronary arterial blood flow is effected by the occurrence of abnormality in the heart. Under normal condition, the simulated endo-epi flow ratio was found to be 0.68. The changes in the flow ratio were observed while varying the septal arterial resistance, mean arterial pressure and intramyocardial pressure individually. The mean flow in the subendocardium was found to decrease at a rate faster than that in the subepicardium with the increase in the septal arterial resistance and the intramyocardial pressure. The same tendency was also observed while the arterial pressure was lowered. From all these observations, it can be concluded that the subendocardium is more vulnerable to ischemic heart diseases than the subepicardium.

Application of Fuzzy Reasoning to Automatic Planning of the Collision-Free Manipulator Path among Opstacles.

Even the potential method, which seems to be most effective for automatic planning of the collision-free manipulator path among obstacles, uses transformation of real space coordinates of the obstacle to joint angle space, so the analyses become difficult or impossible when the manipulator degree of freedom becomes large. This paper proposes the application of fuzzy reasoning to enable handling of the coordinate of the obstacle in the real space coordinate without transformation to joint angle space in order to solve the above-mentioned difficulties, while basically adopting the potential method. Moreover, this proposal adds a great advantage in that much useful different dimensional information can be used for planning, offering a valuable method to further develop this problem. For example, in addition to the information about the deviation from the target and the proximity to the obstacles, the rate of change of these quantities can be included in the planning. This usefulness was confirmed by simulation.

New tetrapolar method using magnetic field for local impedance measurement

The tetrapolar circuit method has been used to detect physiological events as changes in electrical impedance. However, it is still difficult to obtain more meaningful information of local events because of the expanse of current distribution. In order to measure the local impedance change in living tissue, the authors propose a tetrapolar circuit method using a magnetic field. In this method, an eddy current generated in the living tissue by the magnetic field is used in addition to the constant current. The current distribution can be restricted to a local area by combining the eddy current with the constant current. The effectiveness of this method was confirmed by in-vivo measurement of pulsatile waveforms due to the arterial blood flow in the forearm.<<ETX>>