Insulinoma other imaging findings

The other imaging studies include positron emission tomography (PET) and somatostatin receptor Scintigraphy (SRS) which are nuclear studies used for detecting somatostatin receptor especially subtype 2 using radioisotopes of Gallium. The increased uptake of radioligands is suggestive of insulinoma. The metastasis also shows the increased uptake. The sensitivity of PET is increased by doing a CT scan coupled with PET scan. The sensitivity of SRS is 50 to 60% as insulinomas have less somatostatin subtype 2 receptor which is detected by the test.

• Positron emitting radioisotopes of Gallium such as 68 Gallium-DOTATAC, 68 Gallium-DOTATATE, and 68 Gallium-DOTANAC can be used to detect the uptakes in areas of increased somatostatin receptors. The sensitivity is increased when it is coupled with CT scan although it is not approved for routine use in the United States.^[1][2][3]
• Positron emission tomography (PET) may be helpful in the diagnosis of insulinoma. Findings on a PET scan suggestive of insulinoma include:
  • Increased uptake in the affected part of the pancreas.
  • Metastasis can also be detected in the same way.

• Somatostatin receptor scintigraphy(SRS) may be helpful in the diagnosis of pancreatic neuroendocrine tumors including insulinomas. As many insulinomas do not express somatostatin subtype 2 receptors, it is less sensitive(50 to 60%).^{[4][5] [6][7][8]}

Findings on an SRS suggestive of insulinoma include:

• Increased uptake of pentetreotide (synthetic somatostatin analog)
• Increased uptake in sites of metastasis, commonly in hepatic involvement

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