Local excitation universal parallel transmit pulses at 9.4T

Ole Geldschläger, Dario Bosch, Steffen Glaser, Anke Henning

Research output: Contribution to journalArticlepeer-review

Abstract

Purpose: To demonstrate that the concept of “universal pTx pulses” is applicable to local excitation applications. Methods: A database of B0/ (Formula presented.) maps from eight different subjects was acquired at 9.4T. Based on these maps, universal pulses that aim at local excitation of the visual cortex area in the human brain (with a flip angle of 90° or 7°) were calculated. The remaining brain regions should not experience any excitation. The pulses were designed with an extension of the “spatial domain method.” A 2D and a 3D target excitation pattern were tested, respectively. The pulse performance was examined on non-database subjects by Bloch simulations and in vivo at 9.4T using a GRE anatomical MRI and a presaturated TurboFLASH (Formula presented.) mapping sequence. Results: The calculated universal pulses show excellent performance in simulations and in vivo on subjects that were not contained in the design database. The visual cortex region is excited, while the desired non-excitation areas produce the only minimal signal. In simulations, the pulses with 3D target pattern show a lack of excitation uniformity in the visual cortex region; however, in vivo, this inhomogeneity can be deemed acceptable. A reduced field of view application of the universal pulse design concept was performed successfully. Conclusions: The proposed design approach creates universal local excitation pulses for a flip angle of 7° and 90°, respectively. Providing universal pTx pulses for local excitation applications prospectively abandons the need for time-consuming subject-specific B0/ (Formula presented.) mapping and pTx-pulse calculation during the scan session.

Original languageEnglish (US)
Pages (from-to)2589-2603
Number of pages15
JournalMagnetic resonance in medicine
Volume86
Issue number5
DOIs
StatePublished - Nov 2021

Keywords

  • 9.4T
  • high-field MRI
  • local excitation
  • parallel transmit
  • pTx
  • reduced FOV
  • universal pulses

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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