@article{TerekhovElabyadSchreiber2021,
  author    = {Terekhov, Maxim and Elabyad, Ibrahim A. and Schreiber, Laura M.},
  title     = {Global optimization of default phases for parallel transmit coils for ultra-high-field cardiac MRI},
  series = {PLoS One},
  volume    = {16},
  journal   = {PLoS One},
  number    = {8},
  doi       = {10.1371/journal.pone.0255341},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265737},
  year      = {2021},
  abstract  = {The development of novel multiple-element transmit-receive arrays is an essential factor for improving B\(_1\)\(^+\) field homogeneity in cardiac MRI at ultra-high magnetic field strength (B\(_0\) > = 7.0T). One of the key steps in the design and fine-tuning of such arrays during the development process is finding the default driving phases for individual coil elements providing the best possible homogeneity of the combined B\(_1\)\(^+\)-field that is achievable without (or before) subject-specific B\(_1\)\(^+\)-adjustment in the scanner. This task is often solved by time-consuming (brute-force) or by limited efficiency optimization methods. In this work, we propose a robust technique to find phase vectors providing optimization of the B-1-homogeneity in the default setup of multiple-element transceiver arrays. The key point of the described method is the pre-selection of starting vectors for the iterative solver-based search to maximize the probability of finding a global extremum for a cost function optimizing the homogeneity of a shaped B\(_1\)\(^+\)-field. This strategy allows for (i) drastic reduction of the computation time in comparison to a brute-force method and (ii) finding phase vectors providing a combined B\(_1\)\(^+\)-field with homogeneity characteristics superior to the one provided by the random-multi-start optimization approach. The method was efficiently used for optimizing the default phase settings in the in-house-built 8Tx/16Rx arrays designed for cMRI in pigs at 7T.},
  language  = {en}
}