Parathyroid Sestamibi Scan
A parathyroid scan is always performed before minimally invasive parathyroid surgery is performed. The parathyroid Sestamibi scan is not used as diagnostic study or to confirm the presence of hyperparathyroidism. Rather, the test is performed to distinguish or localize the affected parathyroid gland in a patient already diagnosed with the disease.
The parathyroid Sestamibi scan is the preferred test to find an abnormal parathyroid gland. Sestamibi is a small protein that is labeled with the radiopharmaceutical technetium-99m. Tc99m Sestamibi is a very safe and mild radioactive agent that is injected and then preferably absorbed by the abnormal parathyroid gland i.e. parathyroid adenoma. Using an advanced gamma nuclear camera, the abnormal gland can then be visualized and localized in the neck. Normal parathyroid glands typically will not take up the radioactive particles because they are suppressed by an elevated calcium level caused by the abnormal gland. Therefore, a Sestamibi scan of the parathyroid gland will show the one bad parathyroid tumor and it will NOT show normal glands. The other 3 parathyroids are essentially sleeping and not functioning at a normal state. The normal parathyroids produce relatively minimal parathyroid hormone. The sestamibi scan procedure usually takes less than three hours.
Sestamibi Scan Accuracy
The Sestamibi scan can be an extremely accurate and sensitive test; when performed correctly it localizes approximately 70% of parathyroid adenomas. If this test is done at a hospital with less experience, the percent of positive scans decreases. If this nuclear scan is positive, there is a greater than 95% specificity i.e. it is very likely that the active area of the parathyroid scan represents the parathyroid adenoma. An accurate Sestamibi scan is highly dependent on the skill and familiarity of the nuclear technician.