Which radionuclide is used in radionuclide therapy for differentiated thyroid carcinoma, and what is its primary mode of emission used for therapy?

• A Tc-99m; gamma emission
• B F-18; positron (β+) emission
• C Ga-68; gamma emission via positron annihilation
• D I-131; beta (β-) particle emission ✓

Explanation

Iodine-131 (I-131) is used for ablation and treatment of differentiated thyroid carcinoma. It emits beta particles (β-) with a mean energy of ~182 keV and a tissue range of ~0.6–2 mm, delivering localised cytotoxic radiation to iodine-avid thyroid tissue or metastases. I-131 also emits gamma rays (364 keV) used for post-therapy imaging (scintigraphy). Tc-99m is used only for diagnostic imaging (pure gamma emitter). F-18 and Ga-68 are PET tracers used diagnostically, not for therapy.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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