Balanced UTE‐SSFP for 19F MR imaging of complex spectra

Abstract

PurposeA novel technique for highly sensitive detection of multiresonant fluorine imaging agents was designed and tested with the use of dual‐frequency 19F/1H ultrashort echo times (UTE) sampled with a balanced steady‐state free precession (SSFP) pulse sequence and three‐dimensional (3D) radial readout.MethodsFeasibility of 3D radial balanced UTE‐SSFP imaging was demonstrated for a phantom comprising liquid perfluorooctyl bromide (PFOB). Sensitivity of the pulse sequence was measured and compared with other sequences imaging the PFOB (CF2)6 line group including UTE radial gradient‐echo (GRE) at α = 30°, as well as Cartesian GRE, balanced SSFP, and fast spin‐echo (FSE). The PFOB CF3 peak was also sampled with FSE.ResultsThe proposed balanced UTE‐SSFP technique exhibited a relative detection sensitivity of 51 min−1/2 (α = 30°), at least twice that of other sequence types with either 3D radial (UTE GRE: 20 min−1/2) or Cartesian k‐space filling (GRE: 12 min−1/2; FSE: 16 min−1/2; balanced SSFP: 23 min−1/2). In vivo imaging of angiogenesis‐targeted PFOB nanoparticles was demonstrated in a rabbit model of cancer on a clinical 3 Tesla scanner.ConclusionA new dual 19F/1H balanced UTE‐SSFP sequence manifests high SNR, with detection sensitivity more than two‐fold better than traditional techniques, and alleviates imaging problems caused by dephasing in complex spectra. Magn Reson Med 74:537–543, 2015. © 2014 Wiley Periodicals, Inc.