NMTCB Pharmaceutical & Radiopharmaceutical Agents 2

Question 1

Which radiopharmaceutical is most commonly used for parathyroid localization?

Accepted Answer

Tc-99m sestamibi

Answer

Tc-99m sestamibi (MIBI) accumulates in mitochondria-rich parathyroid adenoma cells and is the agent of choice for parathyroid scintigraphy.

Question 2

What is the mechanism by which Tc-99m HMPAO crosses the blood-brain barrier?

Accepted Answer

Lipophilicity allows passive diffusion followed by intracellular trapping

Answer

Tc-99m HMPAO is lipophilic and passively crosses the blood-brain barrier, then converts to a hydrophilic form that becomes trapped intracellularly.

Question 3

Which radionuclide used in PET imaging has the longest physical half-life?

Accepted Answer

F-18 (110 min)

Answer

F-18 has the longest half-life among common PET radionuclides at approximately 110 minutes, making it practical for widespread clinical use.

Question 4

I-131 MIBG is used for imaging of which tumor type?

Accepted Answer

Pheochromocytoma and neuroblastoma

Answer

MIBG (metaiodobenzylguanidine) is a norepinephrine analogue that accumulates in neuroendocrine tumors such as pheochromocytoma and neuroblastoma.

Question 5

What is the recommended patient preparation before administering I-131 for thyroid therapy?

Accepted Answer

Low iodine diet and thyroid hormone withdrawal

Answer

Patients should follow a low iodine diet and discontinue thyroid hormone medication to maximize TSH stimulation and iodine uptake by thyroid tissue.

(NMTCB) Nuclear Medicine Technology Certification Board Practice Test