Method for reduced SAR T1ρ-weighted MRI

✍ Scribed by Andrew J. Wheaton; Arijitt Borthakur; Matthew Corbo; Sridhar R. Charagundla; Ravinder Reddy

• Publisher: John Wiley and Sons
• Year: 2004
• Tongue: English
• Weight: 523 KB
• Volume: 51
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.20141

✦ Synopsis

Abstract

A reduced specific absorption rate (SAR) version of the T~1ρ~‐weighted MR pulse sequence was designed and implemented. The reduced SAR method employs a partial k‐space acquisition approach in which a full power spin‐lock pulse is applied to only the central phase‐encode lines of k‐space, while the remainder of k‐space receives a low‐power spin‐lock pulse. Acquisition of high‐ and low‐power phase‐encode lines are interspersed chronologically to minimize average power deposition. In this way, the majority of signal energy in the central portion of k‐space receives full T~1ρ~‐weighting, while the average SAR of the overall acquisition can be reduced, thereby lowering the minimum safely allowable TR. The pulse sequence was used to create T~1ρ~ maps of a phantom, an in vivo mouse brain, and the brain of a human volunteer. In the images of the human brain, SAR was reduced by 40% while the measurements of T~1ρ~ differed by only 2%. The reduced SAR sequence enables T~1ρ~‐weighted MRI in a clinical setting, even at high field strengths. Magn Reson Med 51:1096–1102, 2004. © 2004 Wiley‐Liss, Inc.