A chemical shift encoding (CSE) approach for spectral selection in fluorine‐19 MRI. Issue 4 (22nd August 2017)

• Record Type: Journal Article
• Authors: Ludwig, Kai D.; Hernando, Diego; Roberts, Nathan T.; van Heeswijk, Ruud B.; Fain, Sean B.
• Is Part Of: Magnetic resonance in medicine. Volume 79:Issue 4(2018)
• Page Start: 2183
• Page End: 2189
• Publication Date: 2017-08-22
• Subjects: fluorine‐19 -- magnetic resonance imaging -- chemical shift encoding; Nuclear magnetic resonance -- Periodicals; Electron paramagnetic resonance -- Periodicals; 616.07548
• DOI: 10.1002/mrm.26874
• Languages: English
• ISSNs: 0740-3194

Abstract

Abstract : Purpose: To develop a chemical shift encoding (CSE) approach for fluorine‐19 MRI of perfluorocarbons in the presence of multiple known fluorinated chemical species. Theory and Methods: A multi‐echo CSE technique is applied for spectral separation of the perfluorocarbon perfluoro‐15‐crown‐5‐ether (PFCE) and isoflurane (ISO) based on their chemical shifts at 4.7 T. Cramér‐Rao lower bound analysis is used to identify echo combinations with optimal signal‐to‐noise performance. Signal contributions are fit with a multispectral fluorine signal model using a non‐linear least squares estimation reconstruction directly from k‐space data. This CSE approach is tested in fluorine‐19 phantoms and in a mouse with a 2D and 3D spoiled gradient‐echo acquisition using multiple echo times determined from Cramér‐Rao lower bound analysis. Results: Cramér‐Rao lower bound analysis for PFCE and ISO separation shows signal‐to‐noise performance is maximized with a 0.33 ms echo separation. A linear behavior (R 2 = 0.987) between PFCE signal and known relative PFCE volume is observed in CSE reconstructed images using a mixed PFCE/ISO phantom. Effective spatial and spectral separation of PFCE and ISO is shown in phantoms and in vivo. Conclusion: Feasibility of a gradient‐echo CSE acquisition and image reconstruction approach with optimized noise performance is demonstrated through fluorine‐19 MRI of PFCE with effective removal of ISO signal contributions. Magn Reson Med 79:2183–2189, 2018. © 2017 International Society for Magnetic Resonance in Medicine.