Biomedical subjects

E Ohdaira

Publications and source records attributed to E Ohdaira.

4 recordsLinked to original sources

PubMed2004

Study for imaging of inside bone using FM-chirp pulse compression system.

We measured the attenuation of ultrasound in animal bone in vitro, and determined successfully the correct dynamic range for the detection of echo signals from inside the bone. It was possible to display a B-mode image of a 6-mm thick porcine rib bone using a high frequency (5 MHz) transducer. However, it was difficult to obtain the image of a large bone (20-mm thick femur). This paper describes a possibility of the improvement for the detection of echoes from inside the bone using the FM-chirp pulse. An ultrasonic wave generator that generates the FM-chirp pulse for a frequency range of 100 KHz to 5 MHz was fabricated. And the pulse was transmitted from a transducer and received by a hydrophone in the water. The received waveform and the frequency spectrum were displayed on an oscilloscope. We measured the amplitude spectrum of the received waves before and after inserting a sample bone between the transducer and the hydrophone. In the experiment, three types of focused transducers (0.5, 1 and 2.25 MHz) and three kinds of sample bones (spine, femur and rib of a pig) were used. From the results of the measurement, we could find the useful information for imaging of inside the bone.

Animals↗

PubMed2000

Water content and its effect on ultrasound propagation in concrete--the possibility of NDE

It is known that water content or moisture affects the strength of concrete. The purpose of this study is to examine the possibility of the NDE of concrete from a knowledge of the relationship between water content and ultrasonic propagation in concrete. The results of measurements made on the ultrasound velocity and the frequency component on ultrasonic propagation as a function of the water content in concrete are reported. Test pieces of concrete made from common materials were made for the fundamental studies. The test piece dimensions were 10 cm in diameter and 20 cm in length. Test pieces were immersed in water for about 50 days to saturate them. To measure the effect of different water contents, test pieces were put in a drying chamber to change the amount of water between measurements. This procedure was repeated until the concrete was completely dried and the weight no longer changed. Water contents were defined as weight percentage to full dried state. Thus water content could be changed from 8% to 0%. Using the pulse transmission method, ultrasonic propagation in the frequency range 20 to 100 kHz was measured as a function of water content. The sound velocity varied gradually from 3000 m/s to 4500 m/s according to the water content. The frequency of maximum transmission also depended on the water content in this frequency range. It is considered that the ultrasonic NDE of concrete strength is feasible.

Journal Article↗

PubMed2000

Improved detection of echo signals from inside bone.

The purpose of the study was to obtain useful information for diagnosing internal abnormalities of bones by ultrasound. We fabricated a transmitting and receiving system mainly targeting the bone and an image processing system using a computer, and studied the attenuation of ultrasound in animal bone (in vitro). The average value was about 37 dB. The examination was able to determine successfully the proper dynamic range for detection, and a B-mode image of the inside of the bone could be displayed. Here we describe a new transmitting and receiving system developed to improve the detection of echo signals from inside bones. In this method, two kinds of high sensitivity transducer were made as follows: (1) 5 HMz frequency, 6.5 mm diameter; (2) 10 HMz frequency, 13 mm diameter. By using this method, detectability of the echo signals can be increased more than with the former system. The results showed that the structure of the bones could be clearly seen in the B-mode images.

Animals↗

PubMed2000

Information contained in the radiating ultrasound during ultrasonic welding

During ultrasonic welding, unnecessary ultrasound together with audible sound is radiated into the air. Audible sound is noisy and uncomfortable, and ultrasound may have bed effects on adjacent equipment. However, it is considered that these sounds potentially contain useful information such as welding state. This article reports the relationship between radiated ultrasound and the change of the welding state during ultrasonic welding. It is known that the welding state can be presumed from the change of the mechanical load impedance, which can be calculated from resonant frequency, motional voltage and the driving current of the vibrating system for the welder when a constant-velocity motional-feedback power oscillator is used. In this study, radiated ultrasound picked up with a microphone and an amplifier is recorded and analyzed with a personal computer. Analyzed results are compared with the change of the mechanical load impedance that is also calculated from the recorded data of the resonant frequency, motional voltage and the driving current of the vibrating system for the welding. Experiments were made on the ultrasonic welding of plastic rods. The relationship between the parameters of radiated ultrasound and the electrical parameters of the vibrating system were compared. The peak amplitude of the radiated ultrasound and the mechanical impedance versus time were very similar. It is shown in this study that radiated ultrasound contains lots of useful information.

Journal Article↗