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In medical ultrasonic measurements, 3-dimensional reconstruction of successive B-mode images is widely used for the macroscopic observation of organs or fetuses. To understand the 3-dimensional images, a stereo display viewed with special glasses (having liquid crystal shutters) and special observation techniques (cross viewing, parallel viewing) have been previously proposed. In this paper, we proposed a system for superimposing a 3-dimensional stereoscopic motion echo image of the heart onto the chest of the subject. A see-through head-mounted display was used for merging the virtual image (3-dimensional heart image) and the real scene (the subject). By the comparing this system with previous ones, the superiority of this system was confirmed in both the resolution of the 3-dimensional heart image and the ease of observation of the image. This system allows observation of the 3-dimensional heart image within the chest of the subject as if looking into the body. In the near future, this system is expected to be beneficial to clinics for purposes such as surgical planning.

In medical echography, Doppler signal analysis is one of the most important diagnostic techniques. In Doppler signal analysis, time-frequency localization techniques are necessary. Many techniques have been proposed for the analysis. Short-time Fourier transform (STFT) is one of the most popular techniques. STFT has a fixed time-frequency window making it inappropriate for analysis of signals having a wide bandwidth. On the other hand, recently, wavelet transform (WT) has received much attention. WT has a flexible time-frequency window adaptable to any time-frequency range. In this paper, we describe an application of STFT and WT to Doppler signal processing. The STFT in this study had a rectangular window and required fast Fourier transform (FFT). On the other hand, the WT with the Morlet function as the mother wavelet was modified to reduce the amount of calculation. Then, we compared the suitability of STFT and WT for application to Doppler signal processing of a simulation and an actual blood flow. In the simulation, a flow having fast and slow velocity changes was assumed. The simulation revealed that the WT could reproduce the fast change of flow velocity, while the STFT could not. Then, a blood flow Doppler signal was measured at a point near the mitral valve in the left ventriculus. Only the WT was capable of reproducing the fast change of flow velocity in the heart. The WT is expected to be useful for analyzing blood flow disorders such as regurgitation.

Based on high-frame-rate digital subtraction echography (HFDSE), we developed a new imaging method to visualize blood flow, i.e., two-dimensional moving target indication (2D-MTI). This method reveals blood flow on a plane by extracting a moving target in the blood flow from ultrasonic B-mode images and tracking it on successive images. Experiments were performed using a model flow path. The results show that particles were extracted from ultrasonic B-mode images, and flow was visualized.

We developed an ultrasonic dynamic imaging system to obtain a three-dimensional echogram in a blood vessel. The method makes it possible to detect the echo signal from objects instantaneously without scanning an ultrasonic beam using a ring array probe. First, we examined the spatial resolution. Second, we performed experiments using a butter block and a copper plate. The results show that this system has a spatial resolution below 1.0 mm, and also that a butter block in a plastic tube and a moving copper plate can be detected by this system.

This paper reports a new intravascular imaging system with a micromotor, revolution characteristics of the micromotor and experimental results using a plastic tube. In this system, an ultrasonic beam is scanned radially by the micromotor instead of a scanning wire. The experimental results show that a cross-sectional image of the tube is reconstructed and that this system has a possibility of application to the observation of the inside of a blood vessel.

The integration of inductors and transformers is necessary for the miniaturization of electrical devices. We have studied micro-magnetic devices such as planar inductors. A planar inductor consists of a planar coil, a magnetic film and an insulator and is fabricated on a substrate by the thin film technique. Here, we propose four basic structures of planar transformers; they are outer and inner types with parallel or superposed coils. Analytical results show that inner types are superior in the coupling factor, which is one of the most important factors of a transformer.

The conventional inductor consists of cores and wound wires, which are obstacles for the integration with other devices. The planar inductor, which has planar coils and magnetic layers in place of cores and wires, is fabricated on a substrate. Therefore it can be integrated with other devices, and it will be a fundamental element for the future magnetic IC. In this paper two kinds of planar inductors are described. One is the outer type, which has the larger inductance than any other planar inductor. The other is the inner type, which has the possibility for a variable inductor.

There is no effective method to measure the size and shape of a plaque of arteriosclerosis in the PTCA operation. Therefore the authors have proposed a method to measure the size of a plaque in a blood vessel. In this paper, they propose a new image reconstruction algorithm for this measurement method. In the new algorithm, they set the model of reflection of the ultrasound such that the ultrasound is reflected in a fixed direction at whole points of measurement space. Inner products of the measured signal and the calculated signals using this model show the probability of a reflector's existence at a point. In addition, the authors can reconstruct a 3-D image of the reflector to display this probability. When using this new algorithm, the authors can obtain an image with a high S/N ratio in a short time.

Describes a three-dimensional (3D) reconstruction and presentation technique to visualize myocardial motion and blood flow using 1 cine-magnetic resonance (MR) image. First, myocardium and blood were extracted on a cine-MR image with certain threshold gray values. Second, with successive two slices of cine-MR image, some slices were interpolated and inserted in the two slices to reconstruct a 3D image. Final, a dynamic image was presented with displaying 3D images sequentially. The 3D dynamic image shows anatomical information such as myocardium and functional information such as blood flow. Furthermore, this method enables to visualize not only normal but also abnormal blood flow in cine-mode.

This paper describes a three-dimensional (3D) ultrasound (US) imaging system, where a commercial ultrasound diagnostic device is used to obtain the coordinates of an US probe and a 3D positioner is used to obtain an US B-mode image. In this system, the B-mode image was projected on a virtual 3D space in a workstation through a transformation matrix and the algorithm for 3D image reconstruction in real time. To evaluate the ability of this system, the authors performed a phantom experiment. The result indicates that the system has the sufficient ability to reconstruct a 3D image of human organs and the availability for intraoperative ultrasonography.

A planar inductor with a closed magnetic circuit structure is proposed. Whereas previous devices constructed by the authors consisted of a coil with magnetic layers above and below, in the present device the coil is surrounded by magnetic material on all four sides, for an increase in inductance from 100 nH to 200 nH. However, the bandwidth falls as a result, from 500 MHz to about 250 MHz. The increase in L is thought to be due primarily to the decrease in reluctance accompanying the addition of magnetic layers.

A planar inductor previously proposed by the authors, consisting of magnetic layers, insulating layers and a coil, has a finite capacitance between the coil and insulating material, and the resulting L-C resonance limits the operable bandwidth. A new type of planar inductor is proposed, in which the insulating layers are omitted to eliminate the stray capacitance, thereby improving the device frequency characteristics.