Findings: Following the intravenous administration of 5.7 mCi of Indium 111 DTPA Octreotide, 4, 24 and 48 hour images were obtained of the whole body in the anterior and posterior projections. An anterior image obtained at 48 hours demonstrates abnormal increased activity within the mediastinum as well as a large focus within the right lobe of the liver. Para-aortic mid abdominal increased activity is also noted.

Diagnosis: Metastatic carcinoid involving the liver, para-aortic lymph nodes and mediastinum.

Discussion: Octreotide is a somatostatin analog used for tumor imaging. Neuroendocrine tumors can be successfully imaged with radiolabeled Octreotide. Specifically, those tumors which contain somatostatin receptors such as carcinoid, pancreatic islet cell, neoplasms, pheochromocytomas as well as neuroblastomas can be visualized. The abnormalities seen on imaging are areas of increased radiopharmaceutical activity.

An accumulation of activity within the liver and bowel can make abdominal interpretation difficult. Therefore, labeling with DTPA enhances renal excretion enhancing conspicuity of lesions.

It has been shown that non-neuroendocrine tumors also exhibit somatostatin receptors and can therefore be imaged with Octreotide. These include pituitary adenomas, non small cell lung carcinoma as well as glial tumors, such as astrocytomas and glioblastomas.

References:
Fischman AJ, Babich JW. Radiolabeled Peptides: A New Class of Imaging Agents.
Nuclear Medicine Annual 1997. Ed. Freeman LM. Lippincott Raven, Philadelphia. 113-117.

Mettler FA, Guiberteau MJ. Essentials in Nuclear Medicine Imaging, 4th Edition,
Philadelphia, W.B. Saunders. 1998:379-382.

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