NMTCB Pharmaceutical & Radiopharmaceutical Agents 3 — Questions and Answers
Question 1: Tc-99m sulfur colloid particles are predominantly removed from circulation by which organ?
- Spleen exclusively
- Liver (60-90%), spleen, and bone marrow via phagocytosis (Correct answer)
- Kidneys via glomerular filtration
- Lungs via capillary trapping
Correct answer: Liver (60-90%), spleen, and bone marrow via phagocytosis
Tc-99m sulfur colloid is phagocytized by reticuloendothelial cells (Kupffer cells) in the liver (60-90%), with the remainder taken up by spleen and bone marrow.
Question 2: What is the primary route of excretion for Tc-99m DTPA after IV administration?
- Hepatobiliary excretion
- Glomerular filtration by the kidneys (Correct answer)
- Exhalation via the lungs
- Fecal excretion via intestinal secretion
Correct answer: Glomerular filtration by the kidneys
Tc-99m DTPA is a small hydrophilic chelate that is freely filtered at the glomerulus and excreted in the urine without tubular secretion or reabsorption.
Question 3: Which radiopharmaceutical is used to assess gastric emptying rate?
- Tc-99m DISIDA
- Tc-99m sulfur colloid in scrambled eggs (Correct answer)
- Tc-99m MAA
- Tc-99m glucoheptonate
Correct answer: Tc-99m sulfur colloid in scrambled eggs
Tc-99m sulfur colloid mixed into scrambled eggs is the standardized solid-phase gastric emptying meal per the Society of Nuclear Medicine protocol.
Question 4: Samarium-153 EDTMP is used therapeutically for which condition?
- Hyperthyroidism
- Painful bone metastases (Correct answer)
- Polycythemia vera
- Renal artery stenosis
Correct answer: Painful bone metastases
Sm-153 EDTMP (lexidronam) localizes in bone metastases via hydroxyapatite binding and delivers beta radiation to palliate metastatic bone pain.
Question 5: The aluminum ion breakthrough test on a Tc-99m generator eluate ensures that aluminum concentration does not exceed:
- 1 µg/mL (1 ppm) (Correct answer)
- 10 µg/mL (10 ppm)
- 0.1 µg/mL (0.1 ppm)
- 100 µg/mL (100 ppm)
Correct answer: 1 µg/mL (1 ppm)
USP limits aluminum ion in Tc-99m eluate to no more than 10 µg Al per mL, but the standard limit commonly cited and tested is ≤10 µg/mL; the regulatory limit is ≤10 µg Al/mL eluate.
Question 6: Which radiopharmaceutical is labeled with In-111 for white blood cell (WBC) imaging?
- In-111 pentetreotide
- In-111 oxine-labeled leukocytes (Correct answer)
- In-111 DTPA
- In-111 capromab pendetide
Correct answer: In-111 oxine-labeled leukocytes
In-111 oxine (8-hydroxyquinoline) is a lipophilic chelate that diffuses into isolated WBCs and binds intracellularly, labeling leukocytes for infection imaging.
Question 7: F-18 FDG accumulation in tumors is primarily due to:
- Increased mitochondrial oxidative phosphorylation
- Overexpression of glucose transporters and hexokinase (Warburg effect) (Correct answer)
- Enhanced fatty acid oxidation in cancer cells
- Increased protein synthesis requiring glucose cofactors
Correct answer: Overexpression of glucose transporters and hexokinase (Warburg effect)
Cancer cells overexpress GLUT transporters and hexokinase, trapping phosphorylated FDG intracellularly via the Warburg effect (aerobic glycolysis).
NMTCB Pharmaceutical & Radiopharmaceutical Agents 3
Tc-99m sulfur colloid particles are predominantly removed from circulation by which organ?