Magnetization-Prepared Shells With Integrated RadiaL and Spirals

Introduction 3D magnetization-prepared fast gradient echo MR sequences, such as MP-RAGE [1], have been widely used for 3D brain volumetric imaging due to high spatial resolution and good contrast between white matter and gray matter. However, these techniques usually require long acquisition time, which increases the probability of motion and decreases clinical throughput. There have been several other methods combined with MP-RAGE to reduce the scan time or enhance the contrast-to-noise ratio, such as parallel imaging [2], centric acquisition order [3], and non-Cartesian trajectories [4, 5]. Combining MP-RAGE with the spherical shells trajectory [5] was demonstrated to effectively capture the peak contrast difference between the white matter (WM) and gray matter (GM). The traditional shells trajectory is composed of concentric spherical shells covered by interleaved helical spirals and additional spirals to cover the “polar icecaps”. The polar icecap sampling can be inefficient and can cause phase discontinuities between interleaves. An improved version of shells, SWIRLS [6] covers shells from pole-to-pole with a single continuous shot combining radial lines and helical spirals. SWIRLS offer more flexibility when it is advantageous to group interleaves on specific shells. This work explores the feasibility of applying the improved SWIRLS trajectory with the MP-RAGE technique.