RF excitation using time interleaved acquisition of modes (TIAMO) to address B1 inhomogeneity in high-field MRI

Stephan Orzada*, Stefan Maderwald, Benedikt Andreas Poser, Andreas K Bitz, Harald H Quick, Mark E Ladd

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


As the field strength and, therefore, the operational frequency in MRI is increased, the wavelength approaches the size of the human head/body, resulting in wave effects, which cause signal decreases and dropouts. Several multichannel approaches have been proposed to try to tackle these problems, including RF shimming, where each element in an array is driven by its own amplifier and modulated with a certain (constant) amplitude and phase relative to the other elements, and Transmit SENSE, where spatially tailored RF pulses are used. In this article, a relatively inexpensive and easy to use imaging scheme for 7 Tesla imaging is proposed to mitigate signal voids due to B(1)(+) field inhomogeneity. Two time-interleaved images are acquired using a different excitation mode for each. By forming virtual receive elements, both images are reconstructed together using GRAPPA to achieve a more homogeneous image, with only small SNR and SAR penalty in head and body imaging at 7 Tesla.

Original languageEnglish
Pages (from-to)327-33
Number of pages7
JournalMagnetic Resonance in Medicine
Issue number2
Publication statusPublished - Aug 2010
Externally publishedYes


  • Adult
  • Algorithms
  • Artifacts
  • Humans
  • Image Enhancement
  • Image Interpretation, Computer-Assisted
  • Magnetic Resonance Imaging
  • Male
  • Pattern Recognition, Automated
  • Phantoms, Imaging
  • Reproducibility of Results
  • Sensitivity and Specificity

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