Takasuke Irie

Comparative Ultrasonographic and Angiographic Study of Carotid Arterial Lesions in Takayasu's Arteritis

The purpose of this study was to compare the usefulness of ultrasonography to that of angiography for studying arterial lesions in Takayasus arteritis. Ultrasonographic and angiographic findings from 44 carotid arteries of 22 patients with Takayasus arteritis (2 men and 20 women; mean age, 41.2 years) were compared. Angiography was used to classify the patency of the carotid arteries into three groups: nonstenotic, stenotic, and occlusive. Ultrasonography was also used to classify the same arteries into four groups: nonstenotic, mildly stenotic, moderately stenotic, and occlusive. Thickness of the wall (intima-media complex) of the carotid artery was measured with high-frequency transducers. Angiography showed 23 carotid arteries to be nonstenotic; 12, stenotic; and 9, occlusive; whereas ultrasonography showed 16 to be nonstenotic; 18, mildly stenotic; 7, moderately stenotic; and 3, occlusive. Results of the two diagnostic modalities correlated closely (P < 0.0001). Ultrasonography, aided by color flow imaging, detected six instances of a marginal but definite blood flow that angiography had failed to reveal. Arterial wall thickness correlated closely with the severity of ultrasonographic stenosis (P < 0.005). This thickness was 1.3 ±0.4 mm in the nonstenotic group, 1.6 ± 0.5 mm in the mildly stenotic group, 2.2 ±0.8 mm in the moderately stenotic group, and 1.9 ±0.2 mm in the occlusive group. Even the walls of the nonstenotic arteries were significantly thicker than those of the normal carotid arteries (0.7 ±0.1 mm, P < 0.01). Ultrasonography appeared to be more useful than angiography in estimating stenotic severity of the carotid artery in Takayasus arteritis. Characteristic ultrasonic findings included luminal stenosis or occlusion on two-dimensional ultrasonograms, decrease in or lack of flow shown by color Doppler flow imaging, and concentric thickening of the carotid arterial walls. Ultrasonographic mural thickness was the most sensitive indicator of early, latent inflammation.

Development of Scanning Method for Puncture Needle-Type Ultrasonography

In this paper, we propose a scanning method for determining the acoustic impedance difference for puncture needle-type ultrasonography using a thin rod. The principle of the proposed scanning method is based on the movements of the end point of a lever. A thin rod is placed on the fulcrum, there by forming a lever. When the end point of the thin rod rotates clockwise forming a circle, the other side of the thin rod moves counterclockwise also forming a circle. By sensing the surface of the sample as a function of the angle made by the thin rod and center axis, scanning can be performed. First, we confirmed that the scanning is possible using the lever; moreover, the movement of the end of the rod is related to that of the other end of the lever. Next, we also confirmed that a one-dimensional image of the amplitude of an interference signal shows the difference in impedance between the polyethylene (PE), acrylic (AC), and polypropylene (PP). The experimental results show that the method is useful for scanning.

Imaging Method for Acoustic Impedance Difference for Puncture Needle-Type Ultrasonography using a Thin Rod with Focusing End Face

In this paper, we propose an imaging method for acoustic impedance difference for puncture needle-type ultrasonography. The difference in acoustic impedance between benign and malignant tissues will provide valuable diagnostic information. In this experiment, a thin rod that has a concave polished end face was constructed using a fused quartz with a diameter of 1 mm and a focus length of 0.3 mm. An ultrasonic wave emitted from the concave end face of the rod is focused on a tissue. The difference in acoustic impedance was determined by the reflection-type interference-based acoustic impedance measurement method. We confirmed that the image shows the difference in impedance between the polyethylene (PE) plate and acrylic rod with a diameter of 3.5 mm embedded therein. The experimental results show that the method is useful for puncture needle-type ultrasonography.

Preliminary Study of Broadband Transducer for Measurement of Bone Characteristics

The purpose of the study is to diagnose bone diseases using the ultrasonic image. We investigate the broadband transducer with a 0.5–5 MHz frequency range. We fabricated two types of transducers with a thin piezoelectric plate bonded with a thick plate resonator. One is an acoustic lens transducer made of flat lead zirconate titanate (PZT) material, and another is a concave transducer made of PZT rod-polymer 1–3 composite material. The application of the transducers to clinical diagnosis involves the measurement of frequency-dependent characteristics of bone by the penetration method. We measured ultrasonic waves radiated from the transducer at the focal point, and performed frequency analysis. As a result, a flat frequency characteristic of the concave transducer was obtained.

Tissue imaging using the transmission of 100-MHz-range ultrasound through a fused quartz fiber

We have studied transmission methods of high-frequency ultrasonic waves through a thin fiber for direct observation of the microscopic image of the tissue. We reported previously that C-mode images of an artificial bone and an animal bone placed in water were obtained by reflection method using a fused quartz fiber as the probe. In this paper, we describe that the C-mode images of the tissue on the glass in water were obtained by penetration method.

Development of Robust Sensing System for Puncture Needle-Type Ultrasonography

In this paper, we propose a robust sensing system that protects a thin rod sensor used in the measurements of acoustic impedance in puncture needle-type ultrasonography. In this ultrasonograpy, an ultrasonic interference method using the thin rod sensor is applied. Since the thin rod made of fused quartz is not robust, a protector is required for the thin rod sensor in in vivo measurement. Therefore, the sensing system has consisted of a thin rod sensor and a hollow pipe with a top cover to protect the sensor. For the observation of a low-impedance material such as biological tissue, the measurement method requires an impedance-transforming layer as the top cover. However, since the optimum thickness of the layer decreases as the measurement frequency increases, the decrease in the thickness causes deformation of the layer. The deformation introduces an error in the measurement. To avoid such a problem, we developed a robust sensing system. The system consists of a quarter-wavelength layer that functions as an impedance transformer and a half-wavelength (or multiple times of a half-wavelength) layer that provides the robustness of the system. We confirmed experimentally the effectiveness of the robust sensing system for acoustic impedance measurement of a tissue sample by the acoustic impedance difference method. The experimental results show that the robust sensing system is useful for puncture needle-type ultrasonography.

FUNDAMENTAL STUDY OF ECHO FROM INSIDE A BONE

In the present study, we investigate the attenuation of ultrasound in bone, using a reflex method to detect the echo and obtain an image of the tissue inside the bone by ultrasound. In the experiment, we developed a standard reflector, and measured the magnitude of reflected waves before and after inserting a bone sample between the transducer and the standard reflector. From the results of the experiment, we could determine the attenuation level of ultrasound in the tissue inside the bone and the dynamic range required for obtaining an image. The possibility of echo detection and obtaining an image was suggested.

A study for B-mode imaging using 100-MHz-range ultrasound through a fused quartz fiber

We have studied transmission methods of high-frequency ultrasonic waves through a thin fiber for direct observation of the microscopic image of the tissue. We reported previously that the C-mode images of the tissue on the glass placed in water were obtained by penetration method using a fused quartz fiber as the probe. In this paper, we describe that the B-mode image of a sample tissue in water was obtained by reflection method using the focused ultrasonic beam.

Effect of repeated US stimulation on adiponectin secretion by adipocytes of obese human subjects

To clarify the effect of the repeated sonication on the adiponectin secretion by adipocytes obtained from obese subjects. Using 1‐MHz continuous‐wave ultrasound at an intensity of 0.50 or 2.1 W/cm2, we sonicated culture flasks of subcutaneous adipocytes obtained from obese human subjects, in a series of 3 sessions of US stimulation applied for a daily total of 15 min. For the measurement of adiponectin secretion, 50 μl of the culture medium was collected from each flask every 24 h after the 1st stimulation. Quantification of adiponectin protein levels in cell culture supernatants was performed with a commercially available ELISA kit recommended by the manufacturer. The adiponectin concentrations in the culture medium of the US stimulation groups rose significantly (p<0.05). Repeated US stimulation may accelerate adiponectin secretion in obese human adipocytes.

A study for propagating ultrasound through transmission line based on cascade-connection resonator model

We are aiming to develop a puncture-type ultrasound microscope by which less invasive settled diagnosis can be executed. To provide in vivo high-resolution imaging of a tumor, we need to scan high frequency ultrasound by rotating an acoustic mirror or an ultrasound oscillator at the tip of a probe. As a driving source device for rotating those, we can use our miniature ultrasonic motor. To narrow the probe while maintaining a smooth rotation of the ultrasonic motor, ultrasound energy for the motor has to be efficiently transmitted from a sound source placed outside the body. In this study, we propose an innovative method for propagating ultrasound using an acoustic transmission line.