On the Localization and Reproducibility of Brain Activation Mapping: Comparison of BOLD, FAIR, and VASO fMRI Techniques
Date Issued
2006
Date
2006
Author(s)
Li, Chia-Wei
DOI
zh-TW
Abstract
Magnetic Resonance Imaging (MRI) provides superior images with high contrast of soft tissues and spatial resolution and wildly used in clinical practices. In the past decade, Functional MRI (fMRI) is used widely to explore the brain function by detecting the hemodynamic change induced by specified cognitive or sensorimotor tasks.
However, traditional Blood Oxygenation Level Dependent (BOLD) fMRI technique contains complicated influences from cerebral blood flow (CBF), cerebral blood volume (CBV), and cerebral metabolic rate of oxygenation (CMRO2). It is difficult to achieve the quantification of parameters and the intra-subject comparison. Therefore, other non-invasive fMRI techniques based on CBF-weighted and CBV-weighted contrasts were developed recently. For example, FAIR and VASO fMRI techniques utilize the adiabatic inversion recovery radiofrequency pulse to label the blood outside the imaging region. Image subtraction or special parameter selection were used to acquire CBF or CBV contrast which reflects neural activation. The major objective of this dissertation is to develop and optimize FAIR and VASO techniques, and also compare with traditional BOLD fMRI. With detecting of T1 value in each voxel, we can obtain the quantified value of regional CBF and its time-course variation.
Inversion recovery EPI T1-mapping sequences are designed to investigate the localization of activation voxels according to the T1 value in each voxel. The results revealed that the activation of FAIR and VASO technique show better localization at gray matters than traditional BOLD fMRI, implicating that their activation are closer to the regions of active neurons. The activated regions measured by three techniques were stable even after 3 months in the reproducibility fMRI studies. The evidence suggests these techniques are sufficient for longitudinal study. Furthermore, we compared these techniques in two cognitive tasks. In a mental arithmetic task, all these techniques achieve similar brain activation. In another visual fMRI experiment, the difference among these techniques implicated an inhibitory phenomenon is resulted from decreased neural activity. The result of VASO indicated that this inhibition in BOLD and FAIR cannot be attributed simply by blood volume changes.
In summary, FAIR and VASO fMRI techniques provide better spatial localization and their results are quantifiable and reproducible. In the future, we will develop the quantified VASO technique and providing better spatial resolution and more coverage of FAIR and VASO techniques. Combining all these information together, they will turn out to be more useful and powerful techniques for brain functional studies.
Subjects
功能性磁振造影
血氧濃度依賴
腦血灌流
腦血容積
縱向研究
fMRI
BOLD
CBF
CBV
longitudinal study
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-95-R93921137-1.pdf
Size
23.31 KB
Format
Adobe PDF
Checksum
(MD5):15e18f0bc3980e076db88aee727cac44