Half-life of perfluorooctylbromide in inner organs determined by fast 19F-NMR imaging

Magnetic resonance imaging characterization of microbial infections

The investigation of microbial infections relies to a large part on animal models of infection, if host pathogen interactions or the host response are considered. Especially for the assessment of novel therapeutic agents, animal models are required. Non-invasive imaging methods to study such models have gained increasing importance over the recent years. In particular, magnetic resonance imaging (MRI) affords a variety of diagnostic options, and can be used for longitudinal studies. In this review, we introduce the most important MRI modalities that show how MRI has been used for the investigation of animal models of infection previously and how it may be applied in the future.

Imaging tumor hypoxia by magnetic resonance methods

Tumor hypoxia results from the negative balance between the oxygen demands of the tissue and the capacity of the neovasculature to deliver sufficient oxygen. The resulting oxygen deficit has important consequences with regard to the aggressiveness and malignancy of tumors, as well as their resistance to therapy, endowing the imaging of hypoxia with vital repercussions in tumor prognosis and therapy design. The molecular and cellular events underlying hypoxia are mediated mainly through hypoxia-inducible factor, a transcription factor with pleiotropic effects over a variety of cellular processes, including oncologic transformation, invasion and metastasis. However, few methodologies have been able to monitor noninvasively the oxygen tensions in vivo. MRI and MRS are often used for this purpose. Most MRI approaches are based on the effects of the local oxygen tension on: (i) the relaxation times of (19)F or (1)H indicators, such as perfluorocarbons or their (1)H analogs; (ii) the hemodynamics and magnetic susceptibility effects of oxy- and deoxyhemoglobin; and (iii) the effects of paramagnetic oxygen on the relaxation times of tissue water. (19)F MRS approaches monitor tumor hypoxia through the selective accumulation of reduced nitroimidazole derivatives in hypoxic zones, whereas electron spin resonance methods determine the oxygen level through its influence on the linewidths of appropriate paramagnetic probes in vivo. Finally, Overhauser-enhanced MRI combines the sensitivity of EPR methodology with the resolution of MRI, providing a window into the future use of hyperpolarized oxygen probes.

(19)F MRI for quantitative in vivo cell tracking

Cellular therapy, including stem cell transplants and dendritic cell vaccines, is typically monitored for dosage optimization, accurate delivery, and localization using noninvasive imaging, of which magnetic resonance imaging (MRI) is a key modality. (19)F MRI retains the advantages of MRI as an imaging modality, and also allows direct detection of labeled cells for unambiguous identification and quantification, unlike typical metal-based contrast agents. Recent developments in (19)F MRI-based in vivo cell quantification, the existing clinical use of (19)F compounds and current explosive interest in cellular therapeutics have brought (19)F imaging technology closer to clinical application. We review the application of (19)F MRI to cell tracking, discussing intracellular (19)F labels, cell labeling and in vivo quantification, as well as the potential clinical uses of (19)F MRI.

NMR spectroscopy in pharmacy

Since drugs in clinical use are mostly synthetic or natural products, NMR spectroscopy has been mainly used for the elucidation and confirmation of structures. For the last decade, NMR methods have been introduced to quantitative analysis in order to determine the impurity profile of a drug, to characteristic the composition of drug products, and to investigate metabolites of drugs in body fluids. For pharmaceutical technologists, solid state measurements can provide information about polymorphism of drug powders, conformation of drugs in tablets etc. Micro-imaging can be used to study the dissolution of tablets, and whole-body imaging is a powerful tool in clinical diagnostics. Taken together, this review covers applications of NMR spectroscopy in drugs analysis, in particular, methods of international pharmacopoeiae, pharmaceutics and pharmacokinetics. The authors have repeated many of the methods describe in their own laboratories.