1989 Fiscal Year Final Research Report Summary
ANALYSIS OF MICROCIRCULATORY HEMODYNAMICS IN MYOCARDIUM USING A NEW INTRAVITAL NEAR-INFRARED FLUORESCENCE MICROSCOPE SYSTEM
| Project/Area Number |
63480222
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Circulatory organs internal medicine
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| Research Institution | University of Tsukuba |
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Principal Investigator |
OHSHIMA Norio Univ. of Tsukuba, Inst. Basic Med. Sci. Professor, 基礎医学系, 教授 (50015971)
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| Co-Investigator(Kenkyū-buntansha) |
SATO Masaaki Univ. of Tsukuba, Inst. Basic Med. Sci. Assist. Prof., 基礎医学系, 講師 (30111371)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Microcirculation / Deep Microvasculature / Near-infrared Fluorescence / Indocyanine Green / Semi-conductor Laser |
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| Research Abstract |
As indocyanine green (ICG) has been shown to emit fluoresence in the near infrared region, its fluorescence is expected to provide information on the deep tissue microcirculation because of the longer wavelength. We attempted to develop an infrared ICG intravital television microscope system to visualize and quantify the microcirculation of relatively thick tissues such as myocardium and skeletal muscles.
To determine optimal conditions for visualizing ICG fluorescence under a microscope, a series of in vitro spectrofluorometric analyses of dye solution were performed.
ICG fluoresence had its peak spectral excitation at a wavelength of 765 nm, and emission spectrum with a broad band between 780 and 840 nm, within which a peak emission wavelength varied considerably depending on the ICG concentration and pH. The intensity of fluorescence showed a maximal value in the ICG concentration range at around 2.0 - 5.0 ug/ml and pH 8-9. HPLC analyses also revealed that ICG predominantly fluoresced when bound to albumin.
To visualize ICG fluorescence in vivo, a commercially available infrared microscope system was modified so as to be equipped with a long enough microscope stand and two different light sources for illumination, i.e., a halogen lamp or a laser beam. Intravital microscopic observation of the ICG fluorescence through a CCD TV camera with microvasculatures of the mesentery, skeletal muscle and myocardium of the rats revealed that microvessels over a range of 15 to 45 um in diameter and location about 200 - 500 um beneath the muscle surface were made to be visualized, although the contrast against background is not satisfactory sharp. Modification of the optical system, such that introducing a light source with higher energy and the bests uited filters are under way to fulfill the ultimate goal for studying the microhemodynamics of the beating heart muscles.
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