Rapid Combo Acquisitions for Sub-Millimeter Isotropic Fluid-Attenuated Inversion Recovery Imaging (Combo-FLAIR)

Hoonjae Lee¹, Jaeseok Park¹

Fluid-attenuated inversion recovery (FLAIR) imaging (1), which employs long inversion recovery (IR) magnetization preparation to selectively nullify cerebrospinal fluid (CSF) signals while retaining a clinically useful T2-weighted contrast, has been widely used for lesion detection in brain. However, since the long time of IR (~ 2000 ms) is required for CSF suppression due to its long T1-relaxation time (~ 4500 ms), imaging time in conventional FLAIR is prohibitively prolonged and spatial resolution is substantially limited. Hence, it is challenging to achieve high-resolution isotropic whole-brain fluid-attenuated imaging for detecting very small lesions in a clinically acceptable imaging time. To resolve this problem, in this work we develop a highly efficient rapid combo acquisition technique for sub-millimeter isotropic FLAIR, wherein instead of long IR preparation rapid gradient echo (PSIF) data (2) is acquired in the periphery of k-space while turbo/fast spin echo (TSE) (3) is encoded in the central region of k-space, simultaneously collecting both low (TSE) and high (PSIF) spatial frequency signals in the ky and kz directions and thus speeding up imaging time.