Cyclotron-produced. Preferred iodine isotope for diagnostic thyroid imaging because:
- 159 keV energy is appropriate for gamma cameras
- 13.2 hour half-life allows imaging without excessive dose
- No beta emission (unlike I-131), so no thyroid ablation or “thyroid stunning”
MIBG (metaiodobenzylguanidine) is a norepinephrine analogue taken up by sympathetic nervous tissue via the norepinephrine reuptake transporter. Used to localize pheochromocytoma, paraganglioma, and neuroblastoma. Cardiac MIBG imaging (adreview) assesses sympathetic denervation in heart failure — reduced uptake (low heart-to-mediastinum ratio) correlates with worse prognosis and guides ICD implantation decisions.
Medications that interfere with MIBG uptake must be held prior to imaging (labetalol, tricyclics, cocaine, pseudoephedrine, calcium channel blockers).