Computed Tomography Test CT Contrast Media and Patient Preparation 3

Question 1

What is the standard iodine concentration range (in mg I/mL) for contrast agents commonly used in diagnostic CT?

Accepted Answer

300–370 mg I/mL

Answer

Most CT contrast agents contain 300–370 mg I/mL; higher concentrations improve vascular opacification while lower volumes can be used to reduce total iodine load.

Question 2

Which intravenous catheter gauge is recommended for power injection during contrast-enhanced CT?

Accepted Answer

18–20 gauge

Answer

An 18–20 gauge IV catheter is recommended for power injection; smaller gauges risk rupture at high flow rates, while larger gauges are unnecessary.

Question 3

A thyroid cancer patient requires radioiodine ablation therapy. Why must iodinated CT contrast be avoided before this treatment?

Accepted Answer

Iodinated contrast saturates the sodium-iodide symporter, blocking therapeutic radioiodine uptake

Answer

Excess stable iodine from contrast saturates thyroid transporters and competes with therapeutic I-131, significantly reducing radioiodine ablation efficacy for 2–8 weeks.

Question 4

What is the primary advantage of using saline flush after contrast injection in CT?

Accepted Answer

Pushes residual contrast into central circulation, improving vascular opacification and reducing dose

Answer

A 30–50 mL saline chaser propels contrast remaining in the IV tubing and peripheral vein into the bloodstream, maximizing the usable contrast bolus.

Question 5

Which pre-medication regimen is typically used for patients with prior moderate contrast reactions undergoing non-emergent contrast CT?

Accepted Answer

Oral prednisone 13 hours, 7 hours, and 1 hour before, plus diphenhydramine 1 hour before

Answer

The standard ACR-recommended steroid premedication protocol uses oral prednisone at three intervals before the scan combined with antihistamine to reduce breakthrough reaction risk.

Computed Tomography Test Practice Test

Computed Tomography Test Practice Test

Computed Tomography Test CT Contrast Media and Patient Preparation 3