Strategies for Improved 3D Small-Tip Fast Recovery (STFR) Imaging

Introduction: Small tip fast recovery (STFR) imaging has been proposed recently as a potential alternative to balanced steady state free precession (bSSFP). STFR relies on a tailored “tip-up” RF pulse (Fig. 1(a)) to achieve comparable signal level and image contrast as bSSFP, but with reduced banding artifacts [1]. 2D STFR imaging can use fast 2D tailored pulses (e.g., spiral) in combination with RF-spoiling [1], but in many applications such as fMRI it is necessary to do 3D imaging [2]. Designing a 3D RF pulse that accurately tailors the excitation pattern to the local B0 inhomogeneity over the entire imaging volume is a challenging and unsolved problem. Here we propose two complementary strategies for improved 3D STFR imaging: First we show that unbalanced non-RF-spoiled STFR imaging (“G-STFR” [3]) is less sensitive to tip-up pulse error than the corresponding RF-spoiled sequence (“RFSTFR”). Second, we propose to use non-slice-selective tailored pulses for both tip-down and tip-up, and present two alternative RF pulse design algorithms.