Mustapha Bouhrara1, Richard G Spencer1. 1. Laboratory of Clinical Investigation, National Institute on Aging, National Institutes of Health, Baltimore, Maryland.
Abstract
PURPOSE: To introduce an accurate, rapid, and practical method for active B1 field mapping based on the double-angle method (DAM) in the steady-state (SS) signal regime. METHODS: We introduced and evaluated the performance of the SS-DAM approach to map the B1 field and compared the results to those calculated from the conventional DAM approach. Similar to DAM, SS-DAM uses the signal intensity ratio of 2 magnitude images acquired with different flip angles using the spoiled gradient recalled echo sequence. However, unlike DAM, in SS-DAM, these 2 spoiled gradient recalled echo images are acquired with very short TR, which allows substantially reduced acquisition time. Numerical, phantom, and in vivo brain imaging analyses, representing a wide range of T1 s and large B1 variation, were conducted. Methods for further accelerating acquisition were also investigated. RESULTS: Our results demonstrate the potential of the SS-DAM approach to be applied widely in the clinical setting. B1 maps derived from SS-DAM were demonstrated to be quantitatively comparable to those derived from DAM but were derived much more rapidly. Large-volume B1 maps were obtained at a field strength of 3 tesla within clinically acceptable acquisition times. CONCLUSION: SS-DAM permits accurate B1 mapping in the clinical setting, with whole-brain coverage in less than 1 min.
PURPOSE: To introduce an accurate, rapid, and practical method for active B1 field mapping based on the double-angle method (DAM) in the steady-state (SS) signal regime. METHODS: We introduced and evaluated the performance of the SS-DAM approach to map the B1 field and compared the results to those calculated from the conventional DAM approach. Similar to DAM, SS-DAM uses the signal intensity ratio of 2 magnitude images acquired with different flip angles using the spoiled gradient recalled echo sequence. However, unlike DAM, in SS-DAM, these 2 spoiled gradient recalled echo images are acquired with very short TR, which allows substantially reduced acquisition time. Numerical, phantom, and in vivo brain imaging analyses, representing a wide range of T1 s and large B1 variation, were conducted. Methods for further accelerating acquisition were also investigated. RESULTS: Our results demonstrate the potential of the SS-DAM approach to be applied widely in the clinical setting. B1 maps derived from SS-DAM were demonstrated to be quantitatively comparable to those derived from DAM but were derived much more rapidly. Large-volume B1 maps were obtained at a field strength of 3 tesla within clinically acceptable acquisition times. CONCLUSION: SS-DAM permits accurate B1 mapping in the clinical setting, with whole-brain coverage in less than 1 min.
Authors: Mustapha Bouhrara; David A Reiter; Christopher M Bergeron; Linda M Zukley; Luigi Ferrucci; Susan M Resnick; Richard G Spencer Journal: Alzheimers Dement Date: 2018-04-19 Impact factor: 21.566
Authors: Mustapha Bouhrara; Abinand C Rejimon; Luis E Cortina; Nikkita Khattar; Richard G Spencer Journal: Magn Reson Imaging Date: 2019-11-12 Impact factor: 2.546
Authors: Matthew Wilcox; Stephen Ogier; Sergey Cheshkov; Ivan Dimitrov; Craig Malloy; Steven Wright; Mary McDougall Journal: IEEE Trans Biomed Eng Date: 2021-05-21 Impact factor: 4.756