Octreoscan

Octreoscan is a nuclear medicine imaging test that is primarily used to detect neuroendocrine tumors. It is a type of scintigraphy that uses a radiolabeled somatostatin analogue, Octreotide, which binds to somatostatin receptors on the surface of the tumor cells.

Procedure

The Octreoscan procedure involves the intravenous injection of the radiopharmaceutical agent, Indium-111-pentetreotide (Indium-111-DTPA-D-Phe-1-octreotide). This agent has a high affinity for somatostatin receptors, particularly subtype 2 and 5, which are overexpressed in many neuroendocrine tumors. After injection, the patient is scanned using a gamma camera to detect the radiation emitted by the Indium-111. The images obtained provide information about the location and size of the tumor.

Clinical Applications

Octreoscan is primarily used in the diagnosis and staging of neuroendocrine tumors, including carcinoid tumors, pancreatic islet cell tumors, and pituitary adenomas. It can also be used to monitor the response to treatment in patients with these tumors. In addition, Octreoscan can be used to determine the suitability of patients for peptide receptor radionuclide therapy (PRRT), a type of targeted therapy that uses radiolabeled somatostatin analogues.

Limitations

While Octreoscan is a valuable tool in the diagnosis and management of neuroendocrine tumors, it has some limitations. Not all neuroendocrine tumors express somatostatin receptors, and therefore, not all tumors can be detected using this method. Furthermore, the resolution of the images obtained is not as high as that of other imaging modalities, such as computed tomography (CT) or magnetic resonance imaging (MRI).

Safety

The radiation exposure associated with Octreoscan is similar to that of other nuclear medicine procedures. The most common side effects are mild and include nausea and vomiting. Serious allergic reactions are rare.

See Also

• Nuclear medicine
• Neuroendocrine tumor
• Somatostatin
• Octreotide
• Indium-111

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