This is a specific scan used for Carcinoid/NETs.
Carcinoids/NETs usually have an affinity for collecting Octreotide, which is a man-made relative (analogue) of the naturally occurring hormone Somatostatin. The manufacturing company “marries” a radioactive isotope (particle), usually Indium111, to the Octreotide and it is injected it into your body. They take a scan after the injection (as a baseline) and then scan again 24 to 72 hours later. It is the later scans which show the places where the material has collected and thus “lights up” on the scan.
There are some people whose tumors have no affinity for, and do not collect, the Octreotide.
Because some tumors have a high affinity for the Octreotide, and some less, the amount of material collected does not show the size of the tumor. It can just be a “hungry” tumor, or a cluster of smaller tumors.
The Octreoscan does not generally show tumors smaller than 1 cm. There are some false positives, such as scar tissue and pooling in the intestines. Having a NETs experienced radiologist read these is important.
Once diagnosed, most patients get an Octreoscan about once a year, give or take, based upon your particular need.