Phase‐sensitive, dual‐acquisition, single‐slab, 3D, turbo‐spin‐echo pulse sequence for simultaneous T2‐weighted and fluid‐attenuated whole‐brain imaging

Abstract

Conventional T(2)-weighted turbo/fast spin echo imaging is clinically accepted as the most sensitive method to detect brain lesions but generates a high signal intensity of cerebrospinal fluid (CSF), yielding diagnostic ambiguity for lesions close to CSF. Fluid-attenuated inversion recovery can be an alternative, selectively eliminating CSF signals. However, a long time of inversion, which is required for CSF suppression, increases imaging time substantially and thereby limits spatial resolution. The purpose of this work is to develop a phase-sensitive, dual-acquisition, single-slab, three-dimensional, turbo/fast spin echo imaging, simultaneously achieving both conventional T(2)-weighted and fluid-attenuated inversion recovery-like high-resolution whole-brain images in a single pulse sequence, without an apparent increase of imaging time. Dual acquisition in each time of repetition is performed, wherein an in phase between CSF and brain tissues is achieved in the first acquisition, while an opposed phase, which is established by a sequence of a long refocusing pulse train with variable flip angles, a composite flip-down restore pulse train, and a short time of delay, is attained in the second acquisition. A CSF-suppressed image is then reconstructed by weighted averaging the in- and opposed-phase images. Numerical simulations and in vivo experiments are performed, demonstrating that this single pulse sequence may replace both conventional T(2)-weighted imaging and fluid-attenuated inversion recovery.