Improved quantitative 19F MR molecular imaging with flip angle calibration and B1-mapping compensation

Matthew J. Goette, Gregory M. Lanza, Shelton D. Caruthers, Samuel A. Wickline

Research output: Contribution to journalArticlepeer-review

11 Scopus citations

Abstract

Purpose To improve 19F flip angle calibration and compensate for B1 inhomogeneities in quantitative 19F MRI of sparse molecular epitopes with perfluorocarbon (PFC) nanoparticle (NP) emulsion contrast agents. Materials and Methods Flip angle sweep experiments on PFC-NP point source phantoms with three custom-designed 19F/1H dual-tuned coils revealed a difference in required power settings for 19F and 1H nuclei, which was used to calculate a calibration ratio specific for each coil. An image-based correction technique was developed using B1-field mapping on 1H to correct for 19F and 1H images in two phantom experiments. Results Optimized 19F peak power differed significantly from that of 1H power for each coil (P-<-0.05). A ratio of 19F/1H power settings yielded a coil-specific and spatially independent calibration value (surface: 1.48-±-0.06; semicylindrical: 1.71-±-0.02, single-turn-solenoid: 1.92-±-0.03). 1H-image-based B1 correction equalized the signal intensity of 19F images for two identical 19F PFC-NP samples placed in different parts of the field, which were offset significantly by ∼66% (P-<-0.001), before correction. Conclusion 19F flip angle calibration and B1-mapping compensations to the 19F images employing the more abundant 1H signal as a basis for correction resulted in a significant change in the quantification of sparse 19F MR signals from targeted PFC NP emulsions.

Original languageEnglish
Pages (from-to)488-494
Number of pages7
JournalJournal of Magnetic Resonance Imaging
Volume42
Issue number2
DOIs
StatePublished - Aug 1 2015

Keywords

  • B correction
  • RF power settings
  • flip angle calibration
  • molecular imaging
  • perfluorocarbon nanoparticles
  • quantitative F MRI

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