An in vivo comparison of the DREAM sequence with current RF shim technology
Kay Nehrke1, Alois M Sprinkart, Peter Börnert
1Philips Research Laboratories, Röntgenstraße 24-26, 22335, Hamburg, Germany, kay.nehrke@philips.com.
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.
