In this paper we present a procedure which automatically extracts soft tissues, such as subcutaneous fat, brain, and cerebral ventricle, from the multislice MRI images of head region, and displays their 3-dimensional images.
Segmentation of soft tissues is done by use of an iterative thresholding. In order to select the optimum threshold value automatically, we introduce a measure to evaluate the goodness of segmentation into this procedure. When the measure satisfies given conditions, iteration of thresholding terminates, and the final result of segmentation is extracted by using the current threshold value.
Since this procedure can execute segmentation and calculation of the goodness measure in each slice automatically, it remarkably decreases efforts of users. Moreover, the 3-dimensional display of the segmented tissues shows that this procedure can extract the shape of each soft tissue with reasonable precision for clinical use.

抄録全体を表示

Several latency correct averaging methods have been studied to estimate underlying signals in the field of event related potential (ERP) experiment as well as some other fields. In this paper, three improved algorithms for estimating average waveform of ERP are proposed. The first is similar to Woolly's adaptive correlation filter and the second is its modified version in frequency domain. Both methods are available for the case in which only one peak to be detected. The third method using a dynamic time warping (DTW) technique can detect several peaks simultaneously and is especially effective for estimating ERP components such as N1, N2, P300 etc.
With this new method, we investigated the ERP in the mental rotation experiment. As a result, it has been revealed that the latency of P300 is increased and also N2 and P2 appear and increase with increment of complexity of the task in the case of simple mental image operation such as mental rotation. Interesting finding is a shifting of superiority of magnitude difference of P300 between hemispheres from right to left with complexity of the tasks.

抄録全体を表示

The electromyographic (EMG) signal which is an indication of the electrical activities in contracting muscle is of value in the study of the motor control mechanism. In a ballistic voluntary movement following a slight sustained contraction, the EMG activity abruptly changes from a tonic discharge to a phasic discharge. An electrical silence or decrease appear just before the onset of the phasic activity. The present study placed focus on a myoelectric activity prior to the ballistic voluntary movement. The EMG activity was processed as a non-stationary stochastic process, and the statistical properties, particularly, the probability density function, were analyzed.
The EMG process remained stationary and normally distributed up to 100 msec before the initiation of the phasic activity. Subsequently, the probability density changed to indicate non-Gaussian property. Statistical test verified this property was statistically significant from 50 msec prior to the onset of the ballistic discharge. As a result of the orthogonal expansion of the probability density function, coefficients of 4th and 6th orders increased from approx. 60 msec before the phasic EMG. These analytical results suggested that the depression of the EMG before the initiation of the ballistic movement was due to an active physiological mechanism with a special programming it the upper center.

抄録全体を表示

Microcomputer assisted ventricular loading system has been developed for the study of cardiac function. This computer system was composed of 16 bit cpu (8086), numeric data processor (8087), and 12bit A/D, D/A converter. The instantaneous velocity of the flow out of, or into the ventricle, and its volume were calculated based on the assumed loading model from measured ventricular pressure, and output to the servo-pump system. This one cycle was done in 420 microsecond. The afterload was composed of peripheral vascular resistance, aortic compliance, characteristic impedance, and the inertia of blood, and the preload was of atrial pressure and valvular resistance to simulate the physiological loading state. Additionally coronary perfusion pressure was controlled according to either calculated aortic pressure or keyboard input. The advantages of the microprocessor control are as follows: 1) the change of parameters is real time, 2) the quantitative evaluation, and the reestablishment of some experimental condition are easy and precise, 3) the control mode is flexible and such complex controls are easily performed by software, as to fix stroke volume, peak pressure or external work by adjusting preload despite the changes of afterload. On the other hand, following three problems were recognized for the improvement of frequency response of the servo system: 1) replacement of potentiometer of contact type by a newly developed optical type device, position sensitive detector (PSD) and light-emitting diode (LED), 2) increase in diameter and decrease in length of the connecting tube between the Bellofram cylinder and ventricle, 3) improvement of the low stiffness of the rolling diaphragm of the cylinder.

抄録全体を表示

We present a simulation model of the age-specific mortality curve f_j(x) which is expressed by a product of age effect g(x) and exogenous effect E(x, j), where x and j represent age and year, respectively. E(x, j) is an integral of carcinogenic exposures in the surroundings from date of birth to year j, and is modelled by the normal distribution function. The age effect can be estimated by g*(x)=f_j*(x)/E(x-j).
Correlation coefficients between observed mortality rates and simulated values were evaluated for lung cancer, gastric cancer and esophageal cancer. The results were 0.993, 0.997, 0.987, respectively. Findings obtained from the model were as follows: 1) Carcinogenic factors in the surroundings had previously increased and are decreasing now as in the case of an epidemic disease; 2) A cohort whose components are 67 years of age in 1980 have been exposed to carcinogenic factors of lung cancer most profoudly. Also the peak of gastric cancer was found in 85 years of age (male) and 90 years of age (female), and that of esophageal cancer was in 79 years of age (male) and 93 years of age (female); 3) Exogenous factors of esophageal cancer are different between the sexes; 4) Many more age-classes are exposed to carcinogenic factors of gastric cancer than other diseases; 5) Effects of carcinogenic factors of lung cancer are changing year by year.

抄録全体を表示

On the concept of the ventricular gradient, we studied location-related (space-axial) analysis of the ECG information with integrating the ECG data of the body surface mapping time-relatedly. The study population consisted of 25 normals, and 56 patients with prior myocardial infarction (MI) who were divided into anterior, inferior and posterior MI. As the first step, the whole myocardium was classified into 3 portions according to the infarct sites. The assumption that the old infarct site is electrically silent proved to be true by analyzing the configuration of the iso-QRST area (G) maps which were converted to the vectors in the multidimensional space. This resulted in the definition of the standard map vectors for each of 4 myocardial sites (anterior, inferior, posterior and the rest). As the next step, the actual G maps were explained by the multiple regression analysis using the standard vectors as the independent variables. All estimated maps fitted well (0.77<R<0.99) to the actual maps, as well as the infarct sites were distinguished from intact ones by the smaller coefficient. In conclusion, we would like to introduce a new EGG approach to the diagnosis of the local myocardial abnormalities.

抄録全体を表示

It would be very useful in the employment of nerve repair at the lesion of injured nerve in continuity if the nerve conductivity could be directly measured. The nerve conduction velocity has in general been calculated indirectly from the distance and latency of the evoked nerve action potentials through the terminal organs such as muscle or skin. However, the shortcoming of this measurement is that it is possible only under the condition where the terminal organ is not denervated. Therefore, in the case where the nerve regeneration does not reach to the terminal organ, the value of conduction velocity is calculated misguidedly as zero. In order to solve this problem, an electronic tester, where a stimulating electrode and a recording one were placed directly to the nerve trunk or the interneural funiculus separately at short distance, was developed for the diagnosis of functional continuity of the injured peripheral nerve.
The following three points were essential in the realization of this system. (1) To use an extremely low-noise differential amplifier with high CMRR, which was realized by a cascode differential stage employing high G_m JFETs. (2) To use a multi-strand low-noise stainless steel electrodes (large effective contact area) for the nerve impulse measurement. (3) To use a specially designed apparatus using a microprocessor and electronic circuits, with which the nerve action potentials evoked by repeated stimulations were processed (synchronous summation, moving average, latency measurement, velocity calculation, etc.), and then the results were displayed and recorded.
The electronic tester was applied clinically in a case suffered with traumatic brachial plexus palsy. Exact diagnosis concerning about functional continuity in each terminal branch of the plexus was obtained intraoperatively. Then neurolysis was performed at proper site of the plexus nerve.

抄録全体を表示

A 3-dimensional computer model was constructed to simulate the ventricular depolarization and repolarization processes in a human heart, and the T wave as well as the QRS-complex were obtained automatically under arbitrary abnormal heart conditions such as bundle branch block and myocardial infarction.
The ventricles with bundle branches and the Purkinje fibers were composed in detail by approximately 50, 000 units. To each unit a different action potential waveform was assigned. The excitation propagates along the bundle branches to the Purkinje fibers and into the ventricles isotropically from the endocardium to the epicardium. Thus the activation time of each unit was determined. With a homogeneous torso model, the body surface potential distributions generated by the EMF sources which are proportional to the spatial gradient of the action potential are calculated by means of the boundary element method. The resulting electrocardiogram, the vectorcardiogram, and the body surface potential map are in good agreement with the observations.
Moreover the ventricular gradient, the primary T wave, and the secondary T wave were also evaluated in the present simulation.
Realistic induction of the T wave based on natural propagation of the excitation front has not been done so far; this is now possible with the present simulation.

抄録全体を表示

In this paper, we study the method of generating a true 3-D image from MRI multiple slices by using the multiplex holography. The purpose in our method is to display effectively the density information distributed in the 3-D space. For making a multiplex hologram any projected image in each direction from multiple slices should be computed. We study computer processing for producing images of good quality from the viewpoint of displaying the density distribution in the 3-D space clearly and discriminating lesions from normal tissues. The following two kinds of processing are studied.
(1) Projection
To generate fastly projections of good quality, the following subjects are examined.
1. Computation method of density values on a projected image from an original slice image.
2. Methods for projection of multiple slices.
3. Interpolation of slices between original neighbouring slices.
4. Composition of several sets of multiple slices in different directions.
(2) Image enhancement
To enhance depth feeling of slices and density values in lesions, the following methods are studied.
1. Enhancement of depth feeling by a weighted sum of slices.
2. Slice enhancement by multiplying the particular slices by weights.
3. Lesion enhancement by thresholding.
4. Lesion enhancement by operations between images with different imaging parameters.
The following are the results; projected images of the quality good enough for constructing a multiplex hologram can be obtained by the simple method proposed in this paper, using four sets of multiple slices in four different directions. The enhancement technique mentioned above was proved to be effective for improving the understandability of 3-D information.

抄録全体を表示

Recently, medical application of low power laser beam has significantly been increasing, but as the mechanism to affection for a living body by laser beam irradiation has not been elucidated at many points, it has become an immediate, essential and important problems to make clear the process of mechanical behavior.
In order to study the mechanism of biological activation on the effect of facilitation to healing for a cut, a gash, an ulcer and etc. by irradiating of laser beam, the author picked up Japanese newt's embryos (Cynops pyrrhogaster), because they can be handled easily as a situation of homogeneous cell group and irradiated them during about one hour by Ar⁺ gaseous laser beam with low energy of 1mW order.
Then, the following results were obtained from the experimental values of velocity of cell cycle and mitotic index (MI) of newt's embryo after irradiation; 1) irradiation of laser beam may become a factor of facilitation for velocity of cell motility, 2) irradiation of laser beam could cause the change of velocity of cell cycle at some points, 3) those phenomena in the case of both 1) and 2) can not be explained merely by thermal ascent.

抄録全体を表示