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Slice-selective RF pulses for in vivo B 1+ inhomogeneity mitigation at 7 tesla using parallel RF excitation with a 16-element coil
| Content Provider | Scilit |
|---|---|
| Author | Setsompop, Kawin Alagappan, Vijayanand Gagoski, Borjan Witzel, Thomas Polimeni, Jonathan Potthast, Andreas Hebrank, Franz Fontius, Ulrich Schmitt, Franz Wald, Lawrence L. Adalsteinsson, Elfar |
| Copyright Year | 2008 |
| Description | Journal: Magnetic Resonance in Medicine Slice-selective RF waveforms that mitigate severe B1+ inhomogeneity at 7 Tesla using parallel excitation were designed and validated in a water phantom and human studies on six subjects using a 16-element degenerate stripline array coil driven with a butler matrix to utilize the eight most favorable birdcage modes. The parallel RF waveform design applied magnitude least-squares (MLS) criteria with an optimized k-space excitation trajectory to significantly improve profile uniformity compared to conventional least-squares (LS) designs. Parallel excitation RF pulses designed to excite a uniform in-plane flip angle (FA) with slice selection in the z-direction were demonstrated and compared with conventional sinc-pulse excitation and RF shimming. In all cases, the parallel RF excitation significantly mitigated the effects of inhomogeneous B1+ on the excitation FA. The optimized parallel RF pulses for human B1+ mitigation were only 67% longer than a conventional sinc-based excitation, but significantly outperformed RF shimming. For example the standard deviations (SDs) of the in-plane FA (averaged over six human studies) were 16.7% for conventional sinc excitation, 13.3% for RF shimming, and 7.6% for parallel excitation. This work demonstrates that excitations with parallel RF systems can provide slice selection with spatially uniform FAs at high field strengths with only a small pulse-duration penalty. |
| Related Links | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2635025/pdf |
| Ending Page | 1432 |
| Page Count | 11 |
| Starting Page | 1422 |
| e-ISSN | 15222594 |
| DOI | 10.1002/mrm.21739 |
| Journal | Magnetic Resonance in Medicine |
| Issue Number | 6 |
| Volume Number | 60 |
| Language | English |
| Publisher | Wiley-Blackwell |
| Publisher Date | 2008-11-24 |
| Access Restriction | Open |
| Subject Keyword | Journal: Magnetic Resonance in Medicine Radiology, Nuclear Medicine and Imaging Parallel Excitation Slice-selective Excitation Rf Inhomogeneity Mitigation Multidimensional Rf Pulse |
| Content Type | Text |
| Resource Type | Article |
