| Summary: | 碩士 === 國立陽明大學 === 生物醫學影像暨放射科學系 === 107 === Purpose: There are two circulatory systems in the human brain, one is hemodynamics of the arteries and veins, and another is hydrodynamics of the cerebrospinal fluid. Both systems contain three physiological rhythms, they are cardiac pulsation, respiration, and Mayer wave. There rhythms are mixed on every pixel of the MR images. In this study, the independent component analysis is used to separate the mixed signals on the MR images. The spatial saturation pulse is used to distinguish the independent signal to a simpler signal that the fluid flowing unidirectionally. Finally, the physiological signal pulsations of different anatomical sites in the brain are analyzed.
Materials and methods: Dynamic MR images were acquired from normal subjects on a 1.5-Tesla MR scanner, with three scans on every slice. The scanning protocols were as follows: without saturation pulse, with a superior saturation pulse, and with a inferior saturation pulse. First, the three groups of images were analyzed to six independent component images and curves by using independent component analysis. Second, the component images were converted to binary images, and there binary images were used as masks to measure original signals. After obtaining original signal intensity curves, the curves were transformed into spectrums by using fast Fourier transform. The last, the spectrum powers of the three rhythms were analyzed.
Results: Through spectrum power, we observed that blood flow in intracranial arteries and veins is affected by cardiac rhythms ,and CSF in ventricles and subarachnoid space is affected by cardiac rhythms and respiratory rhythms. Furthermore, we found that: (1) the spectrum power of cardiac pulsation at artery have statistically significant difference between different spatial saturation; (2) the spectrum power of three physiological rhythms at superior sagittal sinus have statistically significant difference between different spatial saturation conditions; (3) the spectrum power of three physiological rhythms at subarachnoid space or ventricle have no statistically significant difference between different spatial saturation conditions.
Conclusions: We can use independent component analysis method to separate the components of different locations in the brain, and analyze signal of different directional flow by setting the spatial saturation band above or under the target slice.
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