Transverse relaxation time (T2) mapping in the brain with off-resonance correction using phase-cycled steady-state free precession imaging

摘要

Purpose: 46 investigate a new approach for more completely accounting for off-resonance affects in the DESPOT2, (driven equilibrium single pulse observation of T-2) mapping technique. Materials and,Methods:The DESPOT2 method derives T2 information, from fully balanced steady-state free precession,(bSSFP) images acquired over multiple flip angles. Off-resonanee affects, which, present as bands of altered-signal intensity through the bSSFP images, results in erroneous T-2 values in the corresponding calculated maps. Radio-frequency (RF) phase-cycling, in which the phase of the RF pulse is incremented along the pulse'tr,dn; offers a potential method for eliminating these artifacts. In this work we present a general method, refer-red to as DESPOT2, with full modeling (DESPOT2-FM), for deriving T-2, as well as off-resonance frequency, from dual flip angle bSSFP data acquired with two RF phase increments. Results: The method is demonstrated. in vivo, through the acquisition of whole-brain, 1 mm(3) isotopic T-2 maps at 3T and shown to provide near artifact-free maps, even in areas with steep susceptibility induced gradients. Conclusion: DESPOT2-FM offers an efficient method for acquiring high spatial resolution whole-brain T-2 maps, at 3T with high precision and free of artifact.