We developed support system for hepatectomy considering regeneration of the liver after resection. The liver model which consisted of numerous cubic compartments and reproduced three-dimensional structure of the liver was constructed from slice data of the liver measured with X-ray CT, MRI. Resection of clinical case was simulated on the computer, and the resection was reproduced on the model. Three parameters affecting regeneration in each compartment were considered; 1) distance from the porta hepatis to the compartment, 2) metabolic acceleration around the resected plane, 3) metabolic compensation between lobes. These parameters were calculated from three-dimensional structure of the liver, and the three-dimensional distribution of regenerative ability in the model was obtained. Regeneration of the liver was then simulated three dimensionally based on the distribution. Result of simulation was compared with clinical data, and the error was admissible to simulations in the human body. Using our system, it become possible to determine, invasively and preoperatively, the adequate resection which give less damage and good recuperation to a patient.

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We tried to detect the orientation of dermis tissues just beneath skin surface as directional characteristics of sound velocity. We made a pair of transducers, a transmitter and a receiver, to measure sound velocity parallel to skin surface using the inverted phase output of side face of a transducer which usually emits sound waves at right angle with skin surface for ultrasonic observation. First we measured squids which have directional tissues and confirmed that the direction of the tissues was the same with the maximum sound velocity direction. In this case, in order to know how the directional property of tissues is, we adopt the way to see spatial spectrum of changing sound velocity as a function of direction. As a result, it was shown that the direction property was single frequency with a period of π. In addition, as the way to measure the precise maximum sound velocity direction, assuming the change of directional sound velocity as a cosine function and seeing the corelation between them. We used analytical method to regard the shifted phase with maximum corelation value as the precise direction of maximum sound velocity. When we boiled squids and tore them, the direction of torn squid tissues coincided with the direction of maximum sound velocity. Then, we tried to measure the sound velocity of human skin, of forehand and we could confirm a clear directional property, like in the case of squids. This result was the same with the tendency of the result by anatomical study.

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Three-dimensional rendering algorithms are generally categorized as either surface or volume-rendering algorithms. Surface-rendering reveals the surface structure of three-dimensional data, such as X-ray CT and MRI image sets. Volume-rendering allows the internal structure to be seen in addition to the surface structure. Volume rendering relies on the classification of volume elements. This classification consists of two parts; first, to discriminate between the region of organs, bones etc; second, to assign suitable opacities to voxels of each region. Some statistical methods of region discrimination have been reported, but these require large amount of storage and computation. We propose a relatively simple method. It uses as gray level transformation, spatial filtering algorithm, for each tissue type. The method brings not only region discrimination effect but also image processing effect such as noise reduction. We then assign opacities interactively, using a GUI (Graphical User Interface). The effectiveness of the procedure was demonstrated by performing computer simulations with X-ray CT data.

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In this paper, we have made a simulation study of localizing equivalent current dipole (ECD) sources from measured neuromagnetic fields. The purpose of this study is to make clear the problems caused by mis-estimation of the number of ECDs in the localization for single or two dipolar fields. When two-ECDs are localized for single dipolar fields, anomalous convergence results sometimes occur. In this case, the localized ECDs produce dipolar magnetic fields that exceed the measurement area. In the other results, one ECD is localized near the original dipole position and the other ECD position is scattered with initial guesses or noise patterns. In this case, localization results are characterized by some parameters, i. e., low contribution of magnetic fields produced by one ECD, short distance between the localized ECDs or large absolute value of correlation between magnetic fields produced by each ECD. When single ECD is localized for the fields produced by a main dipole and a noise dipole, location errors from the main dipole are more serious, where ECD is localized deeper than the main dipole position rather than shallower. In this case, goodness-of-fit value which is often used to judge the suitability of localization is relatively higher when the errors are large than the value when the errors are small. We have also studied the effects of the contributions of the magnetic fields produced by the target dipoles in two dipolar fields simulation. It was found that when the magnetic fields contribution of one of them is very low, single ECD method is more suitable to localize the main dipole than two-ECDs method, and when the contributions of both dipoles are high, two-ECDs localization is necessary.

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We attempted to investigate relationship among facial temperature of skin, heart beat rhythm and respiratory rhythm. Flames of facial thermal image were recorded every 50ms by IR-camera with a real time recorder and temperature per area of forehead was calculated by a personal computer with 4 transputers. ECG were recorded on a magnetic tape of data recorder and heart rate was computed by R-R interval of the ECG waveform. Experiments were performed in two ways. 1) subjects were sitting on a chair at rest while the temperature was measured. 2) Subjects had exercises in which they pulled rapidly and kept powerfully the back muscle dynamometer for 10s. Temperature fluctuation was analyzed in both kinds of experiment by a spectrum analysis of frequency. Peaks of the fluctuation were coincident with those of respiratory rhythm and of heart beat rhythm, respectively. At rest; 0.17Hz and 0.25Hz. During and after exercise, 0.15Hz and 0.45Hz. It is proved that heart beat rhythm and respiratory rhythm are included in the spectral pattern of the facial temperature.

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This paper studies ability of convergence index to discriminate malignant from benign pulmonary nodules in conventional chest X-ray images. Malignant pulmonary nodules often indicate the radiographic features of vascular convergence and spicule. To quantify such features from images we introduce the convergence index to our system. This feature can quantify the degree of local convergence of linear shadows in the periphery of the nodular shadows and has been originally used to detect local convergence of folds on the stomach wall in double contrast stomach X-ray images. In the new procedure, linear shadows (ex. vascular shadows) in a chest X-ray image are extracted and features concerning the convergence index is calculated using these linear shadows. Then each nodule shadow is classified into benign or malignant classes based on discriminant analysis with several features including the convergence index. The new procedure was applied to real eighty conventional chest X-ray images. As a result, it is demonstrated that the convergence index reflects the extent of the vascular convergence and spicule and can suppress the misclassification rate of the nodular shadows much more than the previous features.

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Functional Electrical Stimulation (FES) is one of effective methods for restoring motor functions of paralyzed extremities. A portable multi-channel FES system for clinical application was developed by our research group in Japan. In the FES system, muscle contraction is controlled by amplitude modulation of stimulus pulse trains with constant pulse width (0.2ms) and stimulus frequency (20Hz). This method, however, does not consider the muscle activation in the normal body such as recruitment order of the motor unit and variation of firing rate. The purposes of this study are to form an FES control method having capability of dealing with different muscle properties and to improve control ability of the FES system. As the FES control method considering muscle property and having improved control ability, we use an amplitude modulation method with pulse frequency modulation. In this paper, the difference between fast and slow muscle responses at various stimulus frequencies was investigated with rabbits. The response of muscle was force at the ankle joint under the isometric condition, when electrical stimulation was applied to the common peroneal nerve for the fast muscle (m. tibialis anterior) and the tibial nerve for the slow muscle (m. triceps surae). First, force of electrically stimulated muscles was examined by the fusion index in order to evaluate fast and slow muscle properties. Then the properties of force versus stimulus frequency were studied. It was made clear from results that the fast muscle developed much larger force than the slow muscle did when stimulus frequency was increased. And more, the fast muscle increased force steeply as the frequency was increased, while the slow muscle increased force gently. These results will be considered as a useful information, when a new FES control method will be made up.

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