Steer‐PROP: a GRASE‐PROPELLER sequence with interecho steering gradient pulses. Issue 5 (14th September 2017)

• Record Type: Journal Article
• Authors: Srinivasan, Girish; Rangwala, Novena; Zhou, Xiaohong Joe
• Is Part Of: Magnetic resonance in medicine. Volume 79:Issue 5(2018)
• Page Start: 2533
• Page End: 2541
• Publication Date: 2017-09-14
• Subjects: GRASE -- PROPELLER -- Steer‐PROP -- phase correction -- diffusion imaging -- k‐space trajectory; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.26898
• Languages: English
• ISSNs: 0740-3194

Abstract

Abstract : Purpose: This study demonstrates a novel PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) pulse sequence, termed Steer‐PROP, based on gradient and spin echo (GRASE), to reduce the imaging times and address phase errors inherent to GRASE. The study also illustrates the feasibility of using Steer‐PROP as an alternative to single‐shot echo planar imaging (SS‐EPI) to produce distortion‐free diffusion images in all imaging planes. Methods: Steer‐PROP uses a series of blip gradient pulses to produce N ( N = 3‐5) adjacent k ‐space blades in each repetition time, where N is the number of gradient echoes in a GRASE sequence. This sampling strategy enables a phase correction algorithm to systematically address the GRASE phase errors as well as the motion‐induced phase inconsistency. Steer‐PROP was evaluated on phantoms and healthy human subjects at both 1.5T and 3.0T for T 2 ‐ and diffusion‐weighted imaging. Results: Steer‐PROP produced similar image quality as conventional PROPELLER based on fast spin echo (FSE), while taking only a fraction (e.g., 1/3) of the scan time. The robustness against motion in Steer‐PROP was comparable to that of FSE‐based PROPELLER. Using Steer‐PROP, high quality and distortion‐free diffusion images were obtained from human subjects in all imaging planes, demonstrating a considerable advantage over SS‐EPI. Conclusion: The proposed Steer‐PROP sequence can substantially reduce the scan times compared with FSE‐based PROPELLER while achieving adequate image quality. The novel k ‐space sampling strategy in Steer‐PROP not only enables an integrated phase correction method that addresses various sources of phase errors, but also minimizes the echo spacing compared with alternative sampling strategies. Steer‐PROP can also be a viable alternative to SS‐EPI to decrease image distortion in all imaging planes. Magn Reson Med 79:2533–2541, 2018. © 2017 International Society for Magnetic Resonance in Medicine.