ABSTRACT
Since publication of the first 19F magnetic resonance images, a wide range of potential applications of fluorine MRI in biomedical imaging have been explored. In particular, since Ahrens and coworkers have shown that distinct cellular populations can be labeled with fluorine-containing compounds and subsequently detected by 19F MRI, this technology has been an accepted method in the molecular imaging toolbox (Ahrens et al., 2005; RuizCabello et al., 2011; Yu et al., 2013). As detailed in other chapters in this book, 19F possesses a high gyromagnetic ratio (94% of 1H), which provides an intrinsically high MR signal. A 100% isotopic abundance and the almost complete lack of any detectable fluorine signal in the mammalian body makes 19F the ideal nucleus for cell tracking and molecular imaging approaches by MRI. Most importantly, 19F provides unambiguous identification of
the cellular or molecular label, and can therefore be considered a gold standard for MR detection specificity of a marker, comparable to the specificity of positron emission tomography (PET) or fluorescence imaging. This excellent detection specificity solves one of the major problems in molecular and cellular MRI approaches that use detection of 1H in combination with iron oxide or lanthanide-based labels (Ahrens and Bulte, 2013). Only recently have novel 1H MRI detection methods, such as PARACEST or highly shifted proton MRI, shown that for 1H the specificity problem can be solved (Aime et al., 2005; Schmidt et al., 2014). The practical usefulness of these methods, however, remains to be shown in further applications.
