Correction for the T1 Effect Incorporating Flip Angle Estimated by Kalman Filter in Cardiac-Gated Functional MRI

• Type of Material: Article
• Authors: Jaemin Shin, Emory University; Sinyeob Ahn, Emory University; Xiaoping Hu, Emory University
• Language: English
• Date: 2013-12-01
• Publisher: Wiley
• Publication Version: Author Accepted Manuscript (After Peer Review)
• Copyright Statement: Copyright © 2013 Wiley Periodicals, Inc., a Wiley company.
• Final Published Version (URL): http://dx.doi.org/10.1002/mrm.24620
• Title of Journal or Parent Work: Magnetic Resonance in Medicine
• ISSN: 0740-3194
• Volume: 70
• Issue: 6
• Start Page: 1626
• End Page: 1633
• Grant/Funding Information: Grant sponsor: Georgia Research Alliance.; Grant sponsor: National Institutes of Health ;Grant number: R01EB002009
• Keywords: FIELD; ORGANIZATION; subcortical imaging; physiological noise; thalamus; B1 inhomogeneity; Life Sciences & Biomedicine; cardiac gating; Radiology, Nuclear Medicine & Medical Imaging; brainstem; LATERAL GENICULATE-NUCLEUS; FMRI; Science & Technology
• Research Categories: Engineering, Biomedical

Abstract

Purpose: To develop an improved and generalized technique for correcting T1-related signal fluctuations (T1 effect) in cardiac-gated functional magnetie resonance imaging (fMRI) data with flip angle estimation. Theory and Methods: Spatial maps of flip angle and T1 are jointly estimated from cardiac-gated time series using a Kalman filter. These maps are subsequently used for removing the T1 effect in the presence of B1 inhomogeneity. The new technique was compared with a prior technique that uses T1 only while assuming a homogeneous flip angle of 90°. The robustness of the new technique is demonstrated with simulated and experimental data. Results: Simulation results revealed that the new method led to increased temporal signal-to-noise ratio across a large range of flip angles, T1s, and stimulus onset asynchrony means compared to the T1 only approach. With the experimental data, the new approach resulted in higher average gray matter temporal signal-to-noise ratio of seven subjects (84 vs. 48). The new approach also led to a higher statistical score of activation in the lateral geniculate nucleus (P < 0.002). Conclusion: The new technique is able to remove the T1 effect robustly and is a promising tool for improving the ability to map activation in fMRI, especially in subcortical regions.