¹⁹F MRI of the Lungs Using Inert Fluorinated Gases: Challenges and New Developments

Abstract

Fluorine‐19 (19F) MRI using inhaled inert fluorinated gases is an emerging technique that can provide functional images of the lungs. Inert fluorinated gases are nontoxic, abundant, relatively inexpensive, and the technique can be performed on any MRI scanner with broadband multinuclear imaging capabilities. Pulmonary 19F MRI has been performed in animals, healthy human volunteers, and in patients with lung disease. In this review, the technical requirements of 19F MRI are discussed, along with various imaging approaches used to optimize the image quality. Lung imaging is typically performed in humans using a gas mixture containing 79% perfluoropropane (PFP) or sulphur hexafluoride (SF6) and 21% oxygen. In lung diseases, such as asthma, chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF), ventilation defects are apparent in regions that the inhaled gas cannot access. 19F lung images are typically acquired in a single breath‐hold, or in a time‐resolved, multiple breath fashion. The former provides measurements of the ventilation defect percent (VDP), while the latter provides measurements of gas replacement (ie, fractional ventilation). Finally, preliminary comparisons with other functional lung imaging techniques are discussed, such as Fourier decomposition MRI and hyperpolarized gas MRI. Overall, functional 19F lung MRI is expected to complement existing proton‐based structural imaging techniques, and the combination of structural and functional lung MRI will provide useful outcome measures in the future management of pulmonary diseases in the clinic. Level of Evidence: 3 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:343–354.

Towards Quantification of Inflammation in Atherosclerotic Plaque in the Clinic – Characterization and Optimization of Fluorine-19 MRI in Mice at 3 T

“…This is also supported by the measured SNR in the aortic arch next to the plaques, which was below the Rose criterion of SNR = 4, meaning that it cannot be distinguished from noise 30 . Moreover, when isoflurane is in- and exhaled through the lungs, it is in a gas phase and its apparent relaxation times are too short to be detected with a TSE pulse sequence 31 , which means that there will be no confounding signal in the lungs. Isoflurane was used in this study because of the need for relatively long anesthesia and the unfeasibility of re-injection during scans, but future studies that aim to maximize specificity and have a limited total anesthesia duration should consider an injected anesthetic such as ketamine-xylazine.…”

Progress in the imaging of COPD: quantitative and functional evaluation

“…A series of ventilation imaging approaches have been used to evaluate the ventilation status of COPD, including the static imaging, dynamic imaging, hyperpolarized inert gas imaging, oxygen enhanced imaging and fluorinated gas imaging [29][30][31][32][33]; which focused on subjective and semiquantitative evaluation, such as ventilation defect, homogeneity and so on. At present, objective and regional evaluation come true.…”

1H‐guided reconstruction of 19F gas MRI in COPD patients

“…7 Magnetic resonance imaging of fluorinated gases may provide a low-cost alternative to hyperpolarized noble gas MRI. 8,9 Due to its large gyromagnetic ratio and the rapid signal recovery, fluorinated gas ( 19 F) imaging is feasible at thermal polarization. Fluorinated gases (eg, SF 6 , C 2 F 6 , C 3 F 8 [perfluoropropane], C 4 F 8 10,11 ) are nontoxic, chemically inert, and can be inhaled over several minutes in a mixture with oxygen.…”