| Project/Area Number |
10480238
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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 | HOKKAIDO UNIVERSITY |
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Principal Investigator |
YAMAMOTO Katsuyuki Hokkaido Univ., Grad.School of Eng., Prof., 大学院・工学研究科, 教授 (10088867)
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| Co-Investigator(Kenkyū-buntansha) |
KUDO Nobuki Hokkaido Univ., Grad.School of Eng., Inst., 大学院・工学研究科, 助手 (30271638)
SHIMIZU Koichi Hokkaido Univ., Grad.School of Eng., Prof., 大学院・工学研究科, 教授 (30125322)
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| Project Period (FY) |
1998 – 2000
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| Project Status |
Completed (Fiscal Year 2000)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2000: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1999: ¥2,700,000 (Direct Cost: ¥2,700,000)
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| Keywords | Ultrasound / Modulation of light / Optical imaging / Spatial resolution / Detection of weak light / Transmitted light / Pulsed light / Pulsed ultrasound / 後方散乱光 / ドプラ効果 / 屈折 / 干渉計 |
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| Research Abstract |
In this study, a new technique to improve a spatial resolution of optical imaging of biological tissues using ultrasound-modulated light was developed, and the following results were obtained.
Study on mechanisms of light modulation by ultrasound
Two high-sensitivity detection systems of ultrasound-modulated light using a photomultiplier or an interferometer were developed. Relationships between a signal intensity of ultrasound-modulated light and a scattering coefficient of a turbid medium were obtained from experiments on a tissue phantom. Based on these relationships, the mechanisms of light modulation by ultrasound and the attenuation of modulated component due to scattering were systematically studied.
Feasibility of utilizing back-scattered light
In optical imaging using transmitted light, a source and a detector must be separately placed on a line, and thickness of an object is restricted by great attenuation of light. Therefore, the feasibility of utilizing back-scattered light was studied using the optical interferometry system that can detect a phase shift of light caused by vibration of scatterers. It was found that an ultrasound-modulated signal can be extracted from back-scattered light by employing the optical interferometry.
Highly sensitive detection of ultrasound-modulated light using a 2-D optical sensor
The interferometry system was further improved so as to collect scattered light and extract a modulated signal from a speckle pattern observed by a 2-D optical sensor. A pulsed laser beam synchronized with ultrasound enabled to use a conventional CCD camera. An attenuation rate of the modulated signal with increase in a scattering coefficient was ten times less than that of the conventional method that detected near-axis transmitted light. It was concluded that this is a promising technique to realize optical imaging of biological tissues with a high spatial resolution.
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