Clinical molecular imaging.

This review summarizes the rapidly growing field of molecular imaging, the spatially localized and/or temporally resolved sensing of molecular and cellular processes in vivo. Molecular imaging is used to map the anatomic locations of specific molecules of interest within living tissue and has enormous potential as a powerful means to diagnose and monitor disease. Molecular imaging agents comprise a targeting component that confers localization and a component that enables external detectability with an imaging modality, such as PET, SPECT, MRI, optical, and ultrasound. The advantages and disadvantages of each of these modalities are discussed in regard to spatial resolution, temporal resolution, sensitivity, and cost. Molecular imaging agents can be divided into three categories, Type A, which bind directly to a target molecule, Type B, which are accumulated by molecular or cellular activity by the target, and Type C, which are undetectable when injected but can be imaged after they are activated by the target. The current status of clinical molecular imaging agents is presented as well as examples of some preclinical applications. The value of molecular imaging is illustrated by some examples for diseases such as cancer, neurological and psychiatric disorders, cardiovascular disease, infection and inflammation, and the monitoring of gene therapy and stem cell therapy.