Biomedical Engineering Reference
In-Depth Information
FIGURE2.1: The tracer principle. Molecular targets are typically addressed
and visualized by injection of tracers, which are consisting of a drug (light
green) to which a flag (dark green; radioactivity, fluorescent dyes, quenched
optical dyes, etc.) is attached. The tracer arrives in organs via blood vessels,
diffuses into the extracellular space and can bind to externalized targets (or-
ange; receptors, etc.) on the cell surface or cross the cell membrane to bind
to intracellular targets. By its flag the tracer emits light or gamma rays to
be detected from outside the organism by SPECT, PET or optical imaging.
Examples of isotopes and dyes used for SPECT, PET and optical imaging are
listed.
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