| Project/Area Number |
15500308
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 Toru Hokkaido Univ., School of Medicine, Department of Health Sciences, Prof., 医学部, 教授 (80261361)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2003: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Keywords | functional MRI / brain function / mapping / hemodynamics / neuronal activity |
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| Research Abstract |
To develop a magnetic resonance imaging (MRI) techtque for mapping of oxygen metabolism which increases in activation foci, this study was conducted as follows.
1.Investigation of MR contrast in capillaries
Hematocrit increases obviously in capillaries of activation foci. To investigate the relation between MR signal and changes in RBC quantity and oxygenation in capillaries, a lower leg was congested by compressing a thigh at several cuff pressures with a rapid cuff inflator and was measured by MRI and NIBS. The occlusion of a thigh made a lower leg hypoxic so ass to increase paramagnetic deoxygenated hemoglobin. MR signal intensity first decreased, then resumed with an increase of compression pressure. This phenomenon is understood by the magnetic susceptibility difference between inside and outside blood vessels. The magnetic susceptibility inside blood vessels increased first with an increase of deoxygenated hemoglobin, then that outside blood vessels increased with an increase of de
… More
oxygenation of myoglobin.
2.Clarification of MR contrast to reflect quantity and oxygenation of RBCs
The magnetic field distortion around RBCs in capillaries reflects tissue oxygenation which changes due to neuronal activation. To clarify the relation between MR contrast and RBC saturation, we investigated the magnetic field distortion around RBCs in detail and found that both blood T2^* and T2 is maximized at the blood oxygenation of 90%. This phenomenon is based on that the magnetic susceptibilities of RBC and plasma equalize at that blood oxygenation. When the magnetic susceptibility of plasma is increased by adding paramagnetic MR contrast agent, the blood oxygenation of maximum blood T2^* and T2 decreased. We clarified how the magnetic field distortion around RBC influences on MR signal.
3.Development of oxygen metabolic imaging
To image oxygen metabolism, MR contrast of tissue area in which oxygen is supplied through capillaries should be concerned. The magnetic susceptibility of RBC in capillaries reflects tissue oxygen concentration. The magnetic field distortion around RBCs is moving along capillaries and changes when the magnetic susceptibility of the plasma is increased by adding paramagnetic MR contrast agent. In particular, where the magnetic susceptibilities of RBC and plasma equalize, there would be no magnetic difference between RBC and plasma and the moving magnetic distortion around RBC disappears, giving rise to maximize T2 in tissue. The MR pulse sequence which is sensitive to the magnetic field distortion around RBC in capillaries is under development. Less
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