Practical considerations for the design of sparse-spokes pulses.
Sparse-spokes pulses are 2D slice-selective pulses that effectively mitigate inhomogeneities in the transmitted RF field and reduce unwanted RF artifacts in MR images. Here we consider the practical design of such pulses for high-field MRI and demonstrate limitations of the technique. We analyze the performance of pulses considering input noise as well as other effects such as saturation and T2( *) relaxation. We discuss in detail the correspondence between the reduction of RF inhomogeneities and the fidelity of the input parameters, such as the transmit B1+ field map and combined phase of the main B0 field and eddy-currents. Results include simulations, utilizing 7 T field maps acquired in phantoms and in-vivo, as well as in-vivo experiments. The necessary performance of system hardware components to achieve significant improvements is described.
Jankiewicz
Marcin
M
Vanderbilt University Institute of Imaging Science, Vanderbilt University, 1161 21st Ave. South, Nashville, TN 37232, USA. m.jankiewicz@vanderbilt.edu
Zeng
Huairen
H
Moore
Jason E
JE
Anderson
Adam W
AW
Avison
Malcolm J
MJ
Welch
E Brian
EB
Gore
John C
JC
D001921:Brain / Q000033:anatomy & histology*; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*