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Diagnostic Tests – Metaiodobenzylguanidine (MIBG) Scan
1. What disease is this test for?
The metaiodobenzylguanidine (MIBG) scan is used to detect pheochromocytoma, particularly when the tumor is occult or not visualized on standard imaging. It is not a screening test; instead, it is used after biochemical confirmation of catecholamine excess (elevated metanephrines, catecholamines, or VMA) when CT or MRI fails to localize the tumor.
2. How is the test done?
MIBG, a compound structurally similar to norepinephrine, is injected intravenously. Because pheochromocytomas arise from adrenergic tissue, they actively take up MIBG. Nuclear imaging is then performed to visualize areas of tracer accumulation, allowing identification of adrenal or extra-adrenal catecholamine-secreting tumors.
3. When do you answer an MIBG scan?
You should select an MIBG scan in a patient who has:
This test is essential because a pheochromocytoma cannot be surgically cured unless it is accurately localized.
1. What disease is this test for?
The metaiodobenzylguanidine (MIBG) scan is used to detect pheochromocytoma, particularly when the tumor is occult or not visualized on standard imaging. It is not a screening test; instead, it is used after biochemical confirmation of catecholamine excess (elevated metanephrines, catecholamines, or VMA) when CT or MRI fails to localize the tumor.
2. How is the test done?
MIBG, a compound structurally similar to norepinephrine, is injected intravenously. Because pheochromocytomas arise from adrenergic tissue, they actively take up MIBG. Nuclear imaging is then performed to visualize areas of tracer accumulation, allowing identification of adrenal or extra-adrenal catecholamine-secreting tumors.
3. When do you answer an MIBG scan?
You should select an MIBG scan in a patient who has:
- Symptoms suggestive of pheochromocytoma (e.g., palpitations, episodic hypertension, intermittent tachycardia, diaphoresis)
- Positive biochemical testing (elevated catecholamines, metanephrines, or VMA)
- Negative or nondiagnostic CT or MRI
This test is essential because a pheochromocytoma cannot be surgically cured unless it is accurately localized.
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