SST and posterior cortical atrophy: Accordingly, various synthetic somatostatin agonists (Figure 6) are available to study the biochemical properties of PCa with neuroendocrine differentiation, but the earliest and most widely used radiolabeled analog of somatostatin is 111In-DTPA-octreotide (octreoscan), which has been approved by the U.S. Food and Drug Administration (FDA) in 1994.