Optimized gradient spoiling of UTE VFA-AFI sequences for robust T1 estimation with B1-field correction

• Published in: Magnetic resonance imaging 2021-10, Vol.82, p.1-8
• Main Authors: Maggioni, Marta B., Krämer, Martin, Reichenbach, Jürgen R.
• Format: Article
• Language: English
• Subjects: Actual Flip angle imaging; B1 mapping; Spoiling; T1 mapping; UTE; Variable Flip angle
• ISSN: 0730-725X; 1873-5894
• DOI: 10.1016/j.mri.2021.06.011

Quantifying T1 relaxation times is a challenge because inhomogeneities of the B1 field have to be corrected to obtain proper values. It is a particular challenge in tissues with short T2⁎ values, for which conventional MRI techniques do not provide sufficient signal. Recently, a B1-field correction technique called AFI (Actual Flip angle Imaging) has been introduced that can be combined with UTE (ultra-short echo-time) sequences, which have much shorter echo times compared to conventional MRI techniques, allowing quantification of signal in short T2⁎ tissues. A disadvantage of AFI is that it requires very long relaxation delays between repetitions to minimize the influence of imperfect spoiling of transverse magnetization on signal behavior. In this work, we propose a novel spoiling scheme for the AFI sequence that efficiently provides accurate B1 correction maps with strongly reduced acquisition time. We validated the method with both phantom and preliminary in vivo results. •AFI is combined with UTE to allow B1 mapping of short T2⁎ tissues.•We propose a spoiling scheme with random directions of the x-y gradients for AFI.•Our method shortens the acquisition time and eliminates the dependency on φ.•In vivo our method yields T1 and T2⁎ values comparable with literature.