High -resolution Fluorine-19 nuclear magnetic resonance imaging and applications to the study of the pulmonary vasculature

Nuclear magnetic resonance (NMR) imaging of fluorine offers a unique way to image the vascular spaces selectively because it has the potential of giving simultaneous anatomical characterisations and oxygen tension measurements. This property can be of great value for studying the pulmonary vasculature, with the proper level of image quality. Theoretical and instrumental difficulties are associated with the imaging of fluorine with NMR. We have developed methods and instrumentation to perform NMR imaging of fluorinated chemicals at high resolution. The methods include software techniques and hardware instruments that allow imaging of static or flowing fluorinated compounds at up to 200 $\mu$m pixel size. The methods were applied to the study of the pulmonary vasculature using an animal model: the rat lung. The fluorinated compound is perfluorotributylamine (FTBA) and it is used in its neat liquid non-emulsified form as well as in the emulsified. The emulsions are blood substitute and thus dynamic studies involving perfusion of the lung are possible. The emulsions are studied biophysically to optimize their characteristics for pulmonary use. The methods are then applied to study the effect of flow on the size of individual vessels and measure the compliance of vessel groups down to approximately 300 $\mu$m. Arterial compliance is characterized using the NMR images. Another application involves the study of the effect of vasoconstrictive hormones, in particular phenylephrine, on the lung. Finally, images of the lung being perfused and inflated with gases of different oxygen tensions are presented to illustrate the potential use for the study of hypoxic pulmonary vasoconstriction