Question:hard
Which of the following is true about contrast radiography?
Which of the following is true about contrast radiography?
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Count iodine atoms per molecule versus the particles formed on dissociation of an ionic monomer.
Updated On: Jun 24, 2026
- In conventional monomeric iodinated contrast media, the iodine atom to solute particle ratio is 3:2.
- Injection into an artery is associated with three times more complications than injection into a vein.
- A test dose should be performed if a contrast reaction is suspected.
- Gadolinium-DTPA crosses the intact blood-brain barrier.
Show Solution
The Correct Option is A
Solution and Explanation
This question is best solved by validating each statement against contrast pharmacology one at a time.
Start with the ratio. The radiographic usefulness of a contrast agent depends on iodine content, while its osmotic toxicity depends on the number of dissolved particles. For a classic ionic monomer, every molecule contributes 3 iodine atoms but splits into 2 particles (an anion plus a cation), so the iodine to particle ratio is 3 to 2. That makes the first statement true.
The claim that arterial injection carries exactly threefold the complications of venous injection is a fabricated number with no basis, so it is false. Performing a test dose is discouraged, because a tiny dose neither predicts nor prevents anaphylactoid reactions and can itself trigger one, so that statement is false too. Finally, gadolinium-DTPA stays out of normal brain tissue and only lights up areas where the blood-brain barrier has broken down, which is the opposite of what option D claims, so it is false.
Only the 3:2 ratio survives scrutiny.
\[\boxed{\text{Iodine to particle ratio is 3:2 in conventional monomeric contrast}}\]
Start with the ratio. The radiographic usefulness of a contrast agent depends on iodine content, while its osmotic toxicity depends on the number of dissolved particles. For a classic ionic monomer, every molecule contributes 3 iodine atoms but splits into 2 particles (an anion plus a cation), so the iodine to particle ratio is 3 to 2. That makes the first statement true.
The claim that arterial injection carries exactly threefold the complications of venous injection is a fabricated number with no basis, so it is false. Performing a test dose is discouraged, because a tiny dose neither predicts nor prevents anaphylactoid reactions and can itself trigger one, so that statement is false too. Finally, gadolinium-DTPA stays out of normal brain tissue and only lights up areas where the blood-brain barrier has broken down, which is the opposite of what option D claims, so it is false.
Only the 3:2 ratio survives scrutiny.
\[\boxed{\text{Iodine to particle ratio is 3:2 in conventional monomeric contrast}}\]
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