Array-optimized composite pulse for excellent whole-brain homogeneity in high-field MRI

Christopher M. Collins, Zhangwei Wang, Weihua Mao, Jieming Fang, Wanzhan Liu, Michael B. Smith

Research output: Contribution to journalArticle

31 Scopus citations

Abstract

A number of methods to improve excitation homogeneity in high-field MRI have been proposed, and some of these methods rely on separate control of radiofrequency (RF) coils in a transmit array. In this work we combine accurate RF field calculations and the Bloch equation to demonstrate that by using a sequence of pulses with individually optimized current distributions (i.e., an array-optimized composite pulse), one can achieve remarkably homogeneous distributions of available signal intensity over the entire brain volume. This homogeneity is greater than that achievable using the same transmit array to produce either a single optimized (or RF shimmed) pulse or a single RF shimmed field distribution in a standard 90x-90y composite pulse arrangement. Simulations indicate that with a very simple array-optimized composite pulse, excellent whole-brain excitation homogeneity can be achieved at up to 600 MHz.

Original languageEnglish (US)
Pages (from-to)470-474
Number of pages5
JournalMagnetic resonance in medicine
Volume57
Issue number3
DOIs
StatePublished - Mar 1 2007

Keywords

  • B
  • Composite pulse
  • High field
  • MRI
  • RF shimming

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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