What is the difference in intravenous (IV) contrast media usage for Computed Tomography (CT) angiogram versus conventional angiogram?

From the Guidelines

The key difference between IV contrast usage in CT angiography versus conventional angiography lies in the administration method and contrast volume, with CT angiography using 100-150 mL of iodinated contrast and conventional angiography using 30-60 mL of contrast directly injected into the vessel of interest. The administration method for CT angiography involves intravenous injection of iodinated contrast delivered through a peripheral vein at 4-5 mL/second using a power injector 1. In contrast, conventional angiography requires direct arterial access with a catheter and uses smaller volumes of contrast injected directly into the vessel of interest in small boluses of 5-10 mL per injection. The contrast concentration is similar in both procedures (300-370 mg iodine/mL), but CT angiography delivers contrast systemically while conventional angiography targets specific vessels.

Key Considerations

• CT angiography captures images of the entire vascular system during a single pass of contrast, while conventional angiography selectively visualizes specific vessels through direct catheterization 1.
• Both procedures require patient preparation including kidney function assessment, hydration, and possible premedication with acetylcysteine or sodium bicarbonate for patients with renal impairment 1.
• CT angiography offers less invasiveness but conventional angiography provides superior spatial resolution and the ability to perform interventions during the same procedure 1.
• The sensitivity and specificity of CT angiography for detection of stenoses >50% diameter are 90% to 100% compared with catheter angiography 1.

Contrast Usage

• CT angiography: 100-150 mL of iodinated contrast (e.g., Omnipaque 350, Isovue 370, or Visipaque 320) delivered through a peripheral vein at 4-5 mL/second using a power injector 1.
• Conventional angiography: 30-60 mL of contrast directly injected into the vessel of interest in small boluses of 5-10 mL per injection.

Recent Guidelines

• The American College of Radiology (ACR) recommends the use of CT angiography for imaging peripheral vascular disease, with multidetector CT scanners enabling rapid scanning of the entire arterial system 1.

From the FDA Drug Label

The usual adult volume as a single injection is 50 mL to 80 mL for the aorta, 30 mL to 60 mL for major branches including celiac and mesenteric arteries, and 5 mL to 15 mL for renal arteries The usual injection volume of OMNIPAQUE 350 for the intravenous digital technique is 30 mL to 50 mL of a 350 mg Iodine/mL solution.

The main difference in IV contrast usage for CT Angiogram (intravenous digital subtraction angiography) vs. Conventional Angiogram is the volume and rate of injection.

• For conventional angiogram, the volume ranges from 5 mL to 80 mL depending on the artery being injected.
• For CT angiogram (intravenous digital subtraction angiography), the usual injection volume is 30 mL to 50 mL at a rate of 7.5 to 30 mL/second. Key points to consider:
• The total volume of contrast medium should not exceed 291 mL of OMNIPAQUE 300 or 250 mL of OMNIPAQUE 350 2.
• The choice of contrast medium and dosage depends on the specific procedure and patient factors.

From the Research

Difference in IV Contrast Usage for CT Angiogram vs. Conventional Angiogram

• The usage of IV contrast in CT angiograms and conventional angiograms differs in terms of the amount and type of contrast medium used.
• A study published in 2019 3 compared the efficacy and safety of catheter-directed CT angiography (CCTA) with a low dose of iodine contrast agent to intravenous CTA in patients undergoing endovascular aortic aneurysm repair (EVAR). The results showed that the amount of contrast medium was significantly lower in CCTA compared to i.v. CTA (23 ± 7 ml vs. 119 ± 15 ml, p<0.0001).
• Another study published in 2020 4 analyzed the ability of coronary CT-angiography (cCTA) to rule out significant coronary artery disease (CAD) during routine pre-TAVI evaluation in patients with high pre-test probability for CAD. The study used a single intravenous bolus of 70 ml iodinated contrast medium and found that cCTA can be incorporated into pre-TAVI CT-evaluation with no need for additional contrast medium.
• A study published in 2009 5 reviewed investigations that evaluated contrast infusion using MDCT with submillimeter detector configuration for coronary artery CT angiography (CTA) and found that literature and survey results suggest a consensus for the use of IV contrast volumes < 100 mL, infusion rate of 5 mL/s, and a saline chaser.

Contrast Medium Usage in Specific Procedures

• For coronary CT-angiography, a study published in 2010 6 compared the image quality and nonserious adverse effects of a low-osmolar contrast medium (iopamidol 370) and an iso-osmolar contrast medium (iodixanol 320) and found that iodixanol 320 can provide both vascular enhancement and image quality similar to iopamidol 370.
• For CT angiography and perfusion imaging in the emergency evaluation of acute stroke, a study published in 2008 7 found that the incidence of contrast-induced nephropathy (CIN) was relatively low (2.9%) and that prompt CTA/CTP imaging of acute stroke, if indicated, need not be delayed in those with no history of renal impairment.

Key Findings

• The amount of contrast medium used in CT angiograms can be significantly lower than in conventional angiograms.
• The type of contrast medium used can affect image quality and adverse effects.
• The usage of IV contrast in CT angiograms and conventional angiograms should be tailored to the specific procedure and patient population.