2007 Fiscal Year Final Research Report Summary
Changes in blood flow due to the static magnetic field of a magnetic resonance scanner
| Project/Area Number |
16300144
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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 |
TAMURA Mamoru Hokkaido University, Faculty of Advanced Life Science, Professor (80089888)
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| Co-Investigator(Kenkyū-buntansha) |
YAMAMOTO Toru Hokkaido University, School of Medicine, Professor (80261361)
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| Project Period (FY) |
2003 – 2006
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| Keywords | magnetic field / MRI / blood / blood flow / EEG |
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| Research Abstract |
To clarify whether a strong static magnetic field affects brain activity such as arousal level, we compared the electroencephalography (EEG) inside an MRI scanner in the presence/absence of the static magnetic field in two different arousal levels of task and rest conditions. Cardiac-related pulsations of head and blood flow induce an electric voltage at each EEG electrode in a static magnetic field. This induced voltage overlaps with the intrinsic EEG signal and becomes a large confounding factor. To extract the information of the intrinsic EEG from the contaminated EEG data measured in a static magnetic field, we developed a new analysis method. No significant difference was observed in the intrinsic EEG in the absence of a magnetic field, whereas in the presence of the static magnetic field, the theta frequency band of the intrinsic EEG increased, especially during the task condition, but other frequency bands did not change. Our results demonstrate that a static magnetic field affects brain activity.
To investigate the influence of the static field of an MR scanner on blood flow, we performed consecutive head imaging at 1.5 and 3.0 T. We confirmed that venous blood oxygenation fluctuated at the sagittal sinus. The power spectra of this fluctuation showed the cardiac and the respiratory components. The ratio between the cardiac and the respiratory components clearly increased with the static magnetic field. This was explained by an increase in blood viscosity and a concomitant increase in blood vessel compliance with an increase in the static magnetic field, The fluctuation of the MR signal intensity of venous blood may reflect the blood vessel compliance, and the spectral analysis of temporal MR images can map the blood vessel compliance. This could be a new technique for early diagnosis of various diseases such as atherosclerosis.
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