A technique that allows biochemical and functional studies of human tumors in vivo. A specific PET tracer is available for the visualization of neuroendocrine gastrointestinal tumors, the serotonin precursor 5-HTP, and PET investigations with this tracer is currently the most sensitive method for detecting small tumors in the thorax and abdomen. Thus, PET can detect small ACTH-producing tumors, small insulinomas and gastrinomas that are difficult to detect with conventional imaging techniques.
