Chemical shift encoding (CSE) for sensitive fluorine-19 MRI of perfluorocarbons with complex spectra

PurposeTo implement a fluorine-19 (F-19) chemical shift encoding (CSE) approach for the sensitive imaging of molecules with multi-resonance spectra to remove their chemical shift displacement (CSD) artifacts, and to characterize its sensitivity versus established pulse sequences. MethodsThe feasibility of CSE spoiled gradient echo (GRE) and balanced steady-state free precession (bSSFP) was first demonstrated in a phantom study. The dependence of the sensitivity of CSE-bSSFP on several pulse sequence parameters was then established, after which the occurrence of out-of-plane excitation was assessed for 2D and 3D techniques. Next, the sensitivity (in mm(-3)s(-0.5)) of both CSE techniques was compared to bSSFP ultrashort echo time (bSSFP-UTE) imaging and multi-chemical-shift-selective turbo spin echo (MCSS-TSE) in a second phantom study. Finally, the sensitivity of the CSE-bSSFP, bSSFP-UTE, and MCSS-TSE pulse sequences was compared in a preliminary in vivo mouse study. ResultsBoth CSE approaches were successfully implemented and resulted in negligible residual CSD artifacts, while large-volume 3D acquisitions should be considered to reduce problems related to out-of-plane excitation. CSE-bSSFP was shown to have a higher sensitivity than the bSSFP-UTE and MCSS-TSE pulse sequences (15.81.3 vs. 11.7 +/- 1.0 vs. 13.3 +/- 0.9mm(-3)s(-0.5), respectively, P<0.001), whereas CSE-GRE technique had a lower sensitivity (4.8 +/- 1.1mm(-3)s(-0.5)). ConclusionCSE F-19 MR imaging enables the unambiguous visualization of compounds with complex spectra, and provides high sensitivity both in vitro and in vivo. Magn Reson Med 79:2724-2730, 2018. (c) 2017 International Society for Magnetic Resonance in Medicine.