FMRI Utilizing Blood Oxygenation Sensitive Steady-state Imaging: Techniques and Applications at High Field
Date Issued
2006
Date
2006
Author(s)
Wu, Ming-Long
DOI
en-US
Abstract
One major challenge of Blood Oxygenation Sensitive Steady-state (BOSS) fMRI is that the frequency band corresponding to highest functional sensitivity is extremely narrow, leading to substantial loss of functional contrast in the presence of magnetic field drifts. In this thesis, a frequency stabilization scheme was proposed for BOSS fMRI at 3T, where an radio-frequency (RF) pulse with very small flip angle was applied before each image scan, with the initial phase of the excited free induction decay signals extracted to reflect the temporal field drifts. A simple infinite impulse response (IIR) filter was further employed to obtain a low-pass filtered estimate of the central reference frequency for the upcoming scan. Experimental results suggest that the proposed scheme was able to stabilize the central reference frequency settings in accordance with the magnetic drifts, with oscillation amplitudes less than 0.5Hz. Phantom studies show that both the slow drifts and the fast fluctuations were prominently reduced for the dynamic BOSS scans, resulting in less than 5% signal variations. Visual fMRI at sub-millimeter in-plane resolution further demonstrated 10-17% activation signals nicely registered in the microvessels within the sulci. It is concluded that the IIR-filtered frequency stabilization is effective for reliable BOSS fMRI at high fields.
Subjects
血氧濃度敏感穩定態
功能性磁振造影
穩定態造影術
頻率穩定技術
無限脈衝響應濾波
blood oxygenation sensitive steady-state
functional magnetic resonance imaging
balanced steady-state free precession
frequency stabilization
infinite impulse response filter
Type
thesis
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