Molecular imaging of tumor metabolism and apoptosis.

Increased metabolism has been found to be one of the most prominent features of malignant tumors. This property led to the development of tracers for the assessment of glucose metabolism and amino acid transport and their application for tumor diagnosis and staging. Prominent examples are fluorodeoxyglucose, methionine and tyrosine analogs, which have found broad clinical application. Since quantitative procedures are available, these techniques can also be used for therapy monitoring. Another approach may be based on the noninvasive detection of apoptosis with tracers for phosphatidyl-serine presentation and/or caspase activation as surrogate markers for therapeutic efficacy. Finally, the evaluation of hypoxia with nitroimidazoles may be a valuable tool for prognosis and therapy planning.