Efficient bloch-siegert B1+ mapping using spiral and echo-planar readouts

Manojkumar Saranathan, Mohammad Mehdi Khalighi, Gary H. Glover, Prachi Pandit, Brian K. Rutt

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


The Bloch-Siegert (B-S) B1+ mapping technique is a fast, phase-based method that is highly SAR limited especially at 7T, necessitating the use of long repetition times. Spiral and echo-planar readouts were incorporated in a gradient-echo based B-S sequence to reduce specific absoprtion rate (SAR) and improve its scan efficiency. A novel, numerically optimized 4 ms B-S off-resonant pulse at + 1960 Hz was used to increase sensitivity and further reduce SAR compared with the conventional 6 ms Fermi B-S pulse. Using echo-planar and spiral readouts, scan time reductions of 8-16 were achieved. By reducing the B-S pulse width by a factor of 1.5, SAR was reduced by a factor of 1.5 and overall sensitivity was increased by a factor of 1.33 due to the nearly halved resonance offset of the new B-S pulse. This was validated on phantoms and volunteers at 7 T. Magn Reson Med 70:1669-1673, 2013. © 2013 Wiley Periodicals, Inc.

Original languageEnglish (US)
Pages (from-to)1669-1673
Number of pages5
JournalMagnetic Resonance in Medicine
Issue number6
StatePublished - Dec 2013
Externally publishedYes


  • Bloch-Siegert method
  • echo-planar readout
  • spiral readout

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging


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