https://scholars.lib.ntu.edu.tw/handle/123456789/332295
Title: | Frequency stabilization using infinite impulse response filtering for SSFP fMRI at 3T | Authors: | Wu, M.-L. Wu, P.-H. Huang, T.-Y. Shih, Y.-Y. Chou, M.-C. Liu, H.-S. Chen, C.-Y. HSIAO-WEN CHUNG |
Keywords: | Balanced steady-state free precession; Blood oxygenation-sensitive steady state; Frequency stabilization; Functional magnetic resonance imaging; IIR filter | Issue Date: | 2007 | Journal Volume: | 57 | Journal Issue: | 2 | Start page/Pages: | 369-379 | Source: | Magnetic Resonance in Medicine | Abstract: | The steady-state free precession (SSFP) method has been shown to exhibit strong potential for distortion-free functional magnetic resonance imaging (fMRI). One major challenge of SSFP fMRI is that the frequency band corresponding to the highest functional sensitivity is extremely narrow, leading to substantial loss of functional contrast in the presence of magnetic field drifts. In this study we propose a frequency stabilization scheme whereby an RF pulse with small flip angle is applied before each image scan, and the initial phase of the free induction decay (FID) signals is extracted to reflect temporal field drifts. A simple infinite impulse response (IIR) filter is 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 can stabilize the frequency settings in accordance with field drifts, with oscillation amplitudes of <0.5 Hz. Phantom studies showed that both slow drifts and fast fluctuations were prominently reduced, resulting in less than 5% signal variations. Visual fMRI at submillimeter in-plane resolution further demonstrated 15% activation signals that were nicely registered in the microvessels within the sulci. It is concluded that the IIR-filtered frequency stabilization is an effective technique for achieving reliable SSFP fMR images at high field strengths. © 2007 Wiley-Liss, Inc. |
URI: | http://www.scopus.com/inward/record.url?eid=2-s2.0-33846839591&partnerID=MN8TOARS http://scholars.lib.ntu.edu.tw/handle/123456789/332295 |
DOI: | 10.1002/mrm.21138 | SDG/Keyword: | Biomedical signal processing; Frequency stability; Impulse response; Low pass filters; Magnetic resonance imaging; Magnetism; Optical fiber communication; Stabilization; Free induction decay signals (FID); Frequency stabilization; Functional magnetic resonance imaging; Functional sensitivities; Infinite impulse response; Oscillation amplitude; Steady state; Steady state free precessions; IIR filters; adult; article; blood oxygenation; female; functional magnetic resonance imaging; human; human experiment; male; normal human; oscillation; phantom; radiofrequency; steady state; theory |
Appears in Collections: | 生醫電子與資訊學研究所 |
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