A pulse sequence for rapid in vivo spin‐locked MRI

Purpose To develop a novel pulse sequence called spin‐locked echo planar imaging (EPI), or (SLEPI), to perform rapid T 1ρ ‐weighted MRI. Materials and Methods SLEPI images were used to calculate T 1ρ maps in two healthy volunteers imaged on a 1.5‐T Sonata Siemens MRI scanner. The head and extremity coils were used for imaging the brain and blood in the popliteal artery, respectively. Results SLEPI‐measured T 1ρ was 83 msec and 103 msec in white (WM) and gray matter (GM), respectively, 584 msec in cerebrospinal fluid (CSF), and was similar to values obtained with the less time‐efficient sequence based on a turbo spin‐echo readout. T 1ρ was 183 msec in arterial blood at a spin‐lock (SL) amplitude of 500 Hz. Conclusion We demonstrate the feasibility of the SLEPI pulse sequence to perform rapid T 1ρ MRI. The sequence produced images of higher quality than a gradient‐echo EPI sequence for the same contrast evolution times. We also discuss applications and limitations of the pulse sequence. J. Magn. Reson. Imaging 2006. © 2006 Wiley‐Liss, Inc.