OBJECT: In the present study the performance of the dual refocusing echo acquisition mode (DREAM) B1 (+) mapping sequence is evaluated for RF shimming in the abdomen at 3 T and validated against existing RF shim technology. MATERIALS AND METHODS: In vivo experiments were performed on 19 normal volunteers using a clinical 3 T dual channel MRI system. For each volunteer three different B1 (+) mapping techniques [DREAM, actual flip angle imaging (AFI) and saturated double angle method (SDAM)] were employed for RF shimming of the liver and to subsequently assess the quality of the obtained RF shim settings in terms of the achieved B1 (+) homogeneity and accuracy of the mean B1 (+). RESULTS: DREAM-based B1 (+) calibration led to an average homogeneity improvement of 39.1 % (AFI = 38.7 %, SDAM = 38.1 %) and a mean B1 (+) of 90.9 % of the prescribed B1 (+) (AFI = 88.9 %, SDAM = 92.0 %). The duration of the B1 (+) calibration scan was reduced from 30 s (AFI) and 15 s (SDAM) to 2.5 s (DREAM). CONCLUSION: DREAM accelerates RF shimming of the liver by an order of magnitude without compromising RF shimming performance.
OBJECT: In the present study the performance of the dual refocusing echo acquisition mode (DREAM) B1 (+) mapping sequence is evaluated for RF shimming in the abdomen at 3 T and validated against existing RF shim technology. MATERIALS AND METHODS: In vivo experiments were performed on 19 normal volunteers using a clinical 3 T dual channel MRI system. For each volunteer three different B1 (+) mapping techniques [DREAM, actual flip angle imaging (AFI) and saturated double angle method (SDAM)] were employed for RF shimming of the liver and to subsequently assess the quality of the obtained RF shim settings in terms of the achieved B1 (+) homogeneity and accuracy of the mean B1 (+). RESULTS: DREAM-based B1 (+) calibration led to an average homogeneity improvement of 39.1 % (AFI = 38.7 %, SDAM = 38.1 %) and a mean B1 (+) of 90.9 % of the prescribed B1 (+) (AFI = 88.9 %, SDAM = 92.0 %). The duration of the B1 (+) calibration scan was reduced from 30 s (AFI) and 15 s (SDAM) to 2.5 s (DREAM). CONCLUSION: DREAM accelerates RF shimming of the liver by an order of magnitude without compromising RF shimming performance.
Authors: Michael J van Rijssel; Josien P W Pluim; Peter R Luijten; Kenneth G A Gilhuijs; Alexander J E Raaijmakers; Dennis W J Klomp Journal: NMR Biomed Date: 2018-03-23 Impact factor: 4.044