Perturbation analysis of the effects of B1+ errors on parallel excitation in MRI.
Design of RF pulses for parallel excitation using phased array transmit coils in MRI requires the B1+ maps that are estimated from B1+ mapping experiments. This paper characterizes the effects of B1+ mapping errors on the resulting excitation pattern using a small perturbation analysis based on linearization of the Bloch equation. The accuracy of the proposed perturbation analysis is validated by Bloch equation simulations based on experimental B1+ maps. The perturbation analysis builds a transparent connection between the B1+ mapping errors and the resulting excitation errors, and can be used to study the robustness of the designed RF pulses to B1+ mapping errors. The proposed method may also supply useful metrics for designing RF pulses that are robust to B1+ mapping errors.
Ma
Chao
C
Department of Electrical and Computer Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA. chaoma2@illinois.edu
Xu
Dan
D
King
Kevin F
KF
Liang
Zhi-Pei
ZP
D000465:Algorithms; D001931:Brain Mapping / Q000379:methods; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D004867:Equipment Design; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D015233:Models, Statistical; D016011:Normal Distribution; D011846:Radio Waves; D015203:Reproducibility of Results; D012815:Signal Processing, Computer-Assisted