NMTCB Pharmaceutical & Radiopharmaceutical Agents 4 — Questions and Answers
Question 1: Tc-99m MAA particles used for lung perfusion imaging should be sized between:
- 1-10 µm
- 10-90 µm (Correct answer)
- 100-500 µm
- 500-1000 µm
Correct answer: 10-90 µm
Tc-99m macroaggregated albumin (MAA) particles are 10-90 µm in diameter, large enough to lodge in pulmonary capillaries (7-10 µm) for perfusion imaging.
Question 2: Which agent is used for hepatobiliary imaging to evaluate acute cholecystitis?
- Tc-99m DTPA
- Tc-99m mebrofenin (DISIDA) (Correct answer)
- Tc-99m MDP
- Tc-99m sestamibi
Correct answer: Tc-99m mebrofenin (DISIDA)
Tc-99m mebrofenin (a hepatobiliary iminodiacetic acid/HIDA analogue) is extracted by hepatocytes and excreted into bile, allowing evaluation of gallbladder filling and biliary patency.
Question 3: Which radiopharmaceutical requires thyroid blocking prior to administration to prevent thyroidal uptake?
- Tc-99m MDP
- I-123 MIBG (Correct answer)
- Tc-99m HMPAO
- Tc-99m MAA
Correct answer: I-123 MIBG
Free iodide released from I-123 MIBG can be taken up by the thyroid; Lugol's solution or potassium iodide is given beforehand to block thyroid uptake.
Question 4: Tc-99m oxidronate (HDP) and Tc-99m MDP are used for bone imaging primarily due to their:
- Binding to red blood cells in bone marrow
- Chemisorption onto hydroxyapatite crystals at sites of osteoblastic activity (Correct answer)
- Active transport into osteoclasts
- Passive diffusion into cortical bone only
Correct answer: Chemisorption onto hydroxyapatite crystals at sites of osteoblastic activity
Diphosphonate agents chemisorb onto calcium hydroxyapatite at sites of increased osteoblastic activity and new bone formation.
Question 5: Which PET radiopharmaceutical is used to assess myocardial viability by evaluating fatty acid metabolism?
- F-18 FDG
- C-11 acetate
- C-11 palmitate (Correct answer)
- N-13 ammonia
Correct answer: C-11 palmitate
C-11 palmitate is a radiolabeled fatty acid that is metabolized by viable myocardium via beta-oxidation, allowing assessment of myocardial fatty acid utilization.
Question 6: The purpose of stannous (tin) chloride in Tc-99m radiopharmaceutical preparation is to:
- Adjust pH to physiologic range
- Reduce pertechnetate (Tc-7+) to a lower oxidation state for chelation (Correct answer)
- Sterilize the preparation
- Increase lipophilicity of the compound
Correct answer: Reduce pertechnetate (Tc-7+) to a lower oxidation state for chelation
Stannous ion (Sn2+) is the reducing agent that reduces pertechnetate from the +7 to a lower oxidation state (+4 or +5), enabling it to bind to the chelating ligand.
Question 7: Y-90 ibritumomab tiuxetan (Zevalin) is a radiolabeled monoclonal antibody that targets which antigen?
- CEA (carcinoembryonic antigen)
- CD20 on B-lymphocytes (Correct answer)
- HER2/neu receptor
- PSMA on prostate cells
Correct answer: CD20 on B-lymphocytes
Ibritumomab tiuxetan targets the CD20 antigen expressed on the surface of B-cells, delivering Y-90 beta radiation to B-cell non-Hodgkin lymphoma.
NMTCB Pharmaceutical & Radiopharmaceutical Agents 4
Tc-99m MAA particles used for lung perfusion imaging should be sized between: