1996 Fiscal Year Final Research Report Summary
Non-destructive detection of material fatigue in artificial heart by ultrasonic spectroscopy.
| Project/Area Number |
07458234
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Biomedical engineering/Biological material science
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| Research Institution | Tohoku University |
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Principal Investigator |
NITTA Shin-ichi Institute of Development, Aging & Cancer, Tohoku University Department of Medical Engineering & Cardiology, Professor, 加齢医学研究所, 教授 (90101138)
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| Co-Investigator(Kenkyū-buntansha) |
KANAI Hiroshi Faculty of Engineering, Tohoku University Department of Electrical Engineering,, 工学部, 助教授 (10185895)
KUSHIBIKI Jun-ichi Faculty of Engineering, Tohoku University Department of Electrical Engineering,, 工学部, 教授 (50108578)
YAMBE Tomoyuki Institute of Development, Aging & Cancer, Tohoku University Department of Medica, 加齢医学研究所, 講師 (70241578)
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| Project Period (FY) |
1995 – 1996
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| Keywords | Artificial heart, / Material Fatigue, / Ultrasound, / Frequency domain analysis, / Acoustic microscopy, / Ultrasonic spectroscopy |
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| Research Abstract |
Left ventricular assist device (LVAD) has been clinically applied for the treatment of severe heart failure in recent years. As the period of using LVAD is expanded to nearly one year, the detection of material damage has been necessitated. In order to detect the material fatigue, low frequency ultrasonic properties of the material were assessed by the frequency domain analysis of the pulsed ultrasound, and the surface morphology of the material was visualized by the acoustic microscopy.
A3.5 MHz linear transducer was placed above the sample in a water tank. The system was modified to access to the rf signals at the output of the time gain controlled (TCG) amplifier, before any significant nonlinear processing, such as compression or rectification, was performed. To observe the frequency dependent characteristics of the received pulse, the Fast Fourier Transform (FFT) of the data was computed. The significant differences of FFT waveforms were observed between new and fatigued materials. Ultrasonic method could detect the material fatigue, although the appearance and the thickness of the samples did not show significant change.
A specially developed scanning acoustic microscope system, operating in the frequency range of 100-200MHz, was employed. In the amplitude image of new material, there were no significant cracks or abnormal structure on the surface. Although the surface seemed to be smooth in the amplitude image, the surface was found to be distorted in the phase image. Very small crack and abnormal powder structure was detected in the amplitude image. In the phase image, the distortion was more prominent than that of new material.
Both in low and high frequencies, ultrasonic approaches to evaluate the material revealed the material damage. Although this study was performed in the static condition, ultrasonic method should be used in the beating condition in the next stage investigation.
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