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

Purpose A novel technique for highly sensitive detection of multiresonant fluorine imaging agents was designed and tested with the use of dual‐frequency 19 F/ 1 H ultrashort echo times (UTE) sampled with a balanced steady‐state free precession (SSFP) pulse sequence and three‐dimensional (3D) radial readout. Methods Feasibility 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 (CF 2 ) 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 CF 3 peak was also sampled with FSE. Results The proposed balanced UTE‐SSFP technique exhibited a relative detection sensitivity of 51μ mol PFOB − 1min −1/2 (α = 30°), at least twice that of other sequence types with either 3D radial (UTE GRE: 20μ mol PFOB − 1min −1/2 ) or Cartesian k‐space filling (GRE: 12μ mol PFOB − 1min −1/2 ; FSE: 16μ mol PFOB − 1min −1/2 ; balanced SSFP: 23μ mol PFOB − 1min −1/2 ). In vivo imaging of angiogenesis‐targeted PFOB nanoparticles was demonstrated in a rabbit model of cancer on a clinical 3 Tesla scanner. Conclusion A new dual 19 F/ 1 H 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.