NucMed Boards Prep
IMAGE INTERPRETATION · PET AND ONCOLOGY

I-123 MIBG Uptake Mechanism in Pheochromocytoma

I-123 MIBG (metaiodobenzylguanidine) scan — whole body images
I-123 MIBG (metaiodobenzylguanidine) scan — whole body images

CC BY 4.0 · Wikimedia Commons · source file

Question

This MIBG scan shows intense focal uptake in the right adrenal region in a patient with hypertensive crises. MIBG localizes to chromaffin tissue by what mechanism, making it useful for detecting pheochromocytoma?

  1. APassive diffusion across the adrenal cell membrane proportional to regional blood flow, with intracellular trapping by mitochondrial binding proteins in steroidogenic cells
  2. BReceptor-mediated endocytosis via glucocorticoid receptors on the adrenal cortex, with retrograde axonal transport to the sympathetic ganglia
  3. CActive uptake via the norepinephrine transporter (NET) into chromaffin cells, the same pathway used by catecholamines
  4. DFDG-like accumulation driven by upregulated hexokinase activity and GLUT overexpression in hyperfunctioning adrenal medullary tissue
Show the answer and explanation

C. Active uptake via the norepinephrine transporter (NET) into chromaffin cells, the same pathway used by catecholamines

MIBG (metaiodobenzylguanidine) is a structural analogue of norepinephrine. It is taken up by chromaffin cells (adrenal medulla, sympathetic nerve terminals) via the norepinephrine transporter (NET) and stored in secretory granules. Pheochromocytomas and paragangliomas (catecholamine-secreting tumors of chromaffin tissue) overexpress NET and accumulate MIBG intensely. MIBG is also used for neuroblastoma imaging and therapy (I-131 MIBG). Certain medications that block NET (tricyclic antidepressants, labetalol, calcium channel blockers) must be stopped before MIBG scanning.

More pet and oncology images

Ga-68 PSMA-11 PET/CT — whole body maximum intensity projectionGa-68 PSMA PET/CT in Prostate Cancer In-111 octreotide (OctreoScan) whole body images — abnormal uptakeGa-68 DOTATATE PET vs OctreoScan for Neuroendocrine Tumors F-18 FDG PET scan — whole bodyDeauville Score 1–2: Complete Metabolic Response F-18 FDG PET/CT — whole body scan with focal uptakeFDG-Avid Benign Disease: Infection and Inflammation Mimics FDG PET — quantitative analysis with SUV measurementHow SUV Is Calculated on FDG PET FDG PET/CT — non-small cell lung cancer stagingFDG PET/CT Staging of Non-Small Cell Lung Cancer
← OctreoScan (In-111 Octreotide): How It LocalizesGa-68 PSMA PET/CT in Prostate Cancer →

All 130 nuclear medicine images by category →

Practise image interpretation in the app

All 130 images as an interactive quiz, alongside 500 NMTCB and ARRT(N) questions with worked explanations, case studies and timed mock exams. 25 questions are free, no card and no account.

Start free — no card

Download on the App StoreGet it on Google Play