Terms Starting with Letter: F fab fragment Antibody fragment produced by enzymatic digestion that still binds antigen. Imaging agents based on fab fragments have accelerated pharmacokinetics over whole antibody-based agents. FDG Fluorodeoxyglucose. (See fluorine-18 –labeled fluorodeoxyglucose) flow Flow is the volume transferred per unit time (e.g., ml/min). fluorescence in situ hybridization (FISH) The use of fluorescence-labeled molecular probes to visualize genes on a chromosome. fluorescence-mediated tomography Method of tomographic reconstruction for in vivo imaging of fluorescent probes. fluorine-18 –labeled fluorodeoxyglucose (FDG) A 2-deoxyglucose that is radiolabeled for PET imaging. FDG is a derivative of glucose, the predominant energy source of tumors, yet it is not fully metabolized and is therefore trapped in malignant cells. FDG is used for imaging in oncology, cardiology, and neurology. fluorochrome A fluorescent dye used to label target molecules to render the molecule, cell or tissue fluorescent for imaging purposes. flux Flux is the change in quantity per unit time (e.g., g/min). folate receptor Receptor for the vitamin folate. Often overexpressed in brain, ovarian and other types of cancers, labeled folate can be used for diagnosis or therapy purposes. fullerene Named after Buckminster Fuller, Fullerene are any of the family of molecules primarily made up of carbon atoms and arranged in especially stable configurations (buckyball, nanotube). The may be used for the delivery of contrast or therapy agents in molecular imaging. functional imaging In vivo imaging and diagnosis of physiologic states and dynamic processes. fusion protein Macromolecular product of expressed hybrid gene consisting of two or more covalently linked proteins.