Somatostatin Receptor Scintigraphy-Spect

The evidence of overexpression of somatostatin receptors by primary and metastatic malignant disease, mainly of neuroendocrine origin, has prompted a worldwide search for radiolabeled somatostatin analogues for use in somatostatin receptor scintigraphy (SRS). The first somatostatin analogue-based radiopharmaceutical, 111In-DTPA-D-Phe1-octreotide, has become a "gold standard" in the localization, staging, and therapy follow-up in patients with neuroendocrine tumors. Due to the wide availability and cost-effectiveness of 99mTc for routine clinical applications, further, the technetium-99m-labeled somatostatin analogues were developed, such as 99mTc-EDDA/HYNIC-Tyr3-octreotide or 99mTc-N4-Tyr3-octreotate. Today, the 99mTc-labeled somatostatin analogues offer a favorable pharmacokinetics, higher spatial resolution, and lower radiation doses, and are gradually replacing 111In-DTPA-D-Phe1-octreotide for routine SRS.