What are the findings of atherosclerosis on computed tomography (CT) with intravenous (IV) contrast?

From the Guidelines

Atherosclerosis on CT with IV contrast is best evaluated using CT angiography (CTA) with thin-section acquisitions timed to coincide with peak arterial or venous enhancement, as it provides high sensitivity for thrombus and dissection, and allows for accurate measurement of luminal narrowing. When IV contrast is administered, it enhances the vessel lumen, creating clear contrast between the flowing blood and the atherosclerotic plaques, which is essential for distinguishing between different types of plaques and evaluating the degree of stenosis 1. The calcified components of plaques appear as high-density areas, while soft, lipid-rich plaques may be less visible. CT angiography with contrast is particularly useful for evaluating the degree of stenosis, which is important for clinical decision-making, as it helps differentiate between the vessel lumen and surrounding tissues, allowing for accurate measurement of luminal narrowing 1.

Some key points to consider when evaluating atherosclerosis on CT with IV contrast include:

• The use of electrocardiogram-gated CTA to minimize cardiac motion artifact and allow for accurate orthogonal measurement of the ascending thoracic aorta 1
• The importance of timing, reconstructions or reformats, and 3-D renderings in CTA, as these elements are essential for accurate evaluation of atherosclerotic disease 1
• The potential limitations of CTA, including streak artifact from implanted devices, variable quality of images through the aortic root and coronary vessels due to cardiac motion in nongated studies, and the need for IV iodinated contrast 1
• The value of multiphase CTA, including delayed-contrast images, for evaluation of patients who have had either open or endovascular TAA repair and for patients who need pre-operative treatment planning 1.

Overall, the use of CT angiography with IV contrast is a valuable tool for evaluating atherosclerosis, as it provides high-quality images of the arterial walls and allows for accurate measurement of luminal narrowing, which is essential for clinical decision-making 1.

From the FDA Drug Label

The pharmacokinetics of iohexol in both normal and abnormal tissue have been shown to be variable Contrast enhancement appears to be greatest immediately after bolus administration (15 seconds to 120 seconds). Utilization of a continuous scanning technique (ie, dynamic CT scanning) may improve enhancement and diagnostic assessment of tumor and other lesions such as abscess, occasionally revealing unsuspected or more extensive disease A vascularized lesion is characterized by an increase in CT number in the few minutes after a bolus of intravascular contrast agent; it may be malignant, benign, or normal tissue, but would probably not be a cyst, hematoma, or other nonvascular lesion Because unenhanced scanning may provide adequate diagnostic information in the individual patient, the decision to employ contrast enhancement, which may be associated with risk and increased radiation exposure, should be based upon a careful evaluation of clinical, other radiological, and unenhanced CT findings.

Atherosclerosis on CT with IV contrast can be evaluated using iohexol.

• Key points:
  • Contrast enhancement is greatest immediately after bolus administration.
  • Dynamic CT scanning may improve diagnostic assessment.
  • Vascularized lesions can be distinguished from non-vascular lesions.
  • The decision to use contrast enhancement should be based on careful evaluation of clinical and radiological findings 2.
• Clinical decision: Iohexol can be used to evaluate atherosclerosis on CT with IV contrast, but the decision to use contrast enhancement should be made on a case-by-case basis.

From the Research

Imaging Modalities for Atherosclerosis

• Computed Tomography (CT) with intravenous (IV) contrast is a commonly used imaging modality for detecting atherosclerosis, as it allows for the visualization of the coronary arteries and the detection of luminal stenoses and atherosclerotic plaque 3.
• The use of CT with IV contrast has been shown to be effective in identifying atherosclerosis and predicting future cardiac events, with a high predictive value of coronary artery calcium (CAC) for future cardiac events 3.
• Coronary CT angiography (CTA) is a more complex data acquisition protocol that requires higher spatial and temporal resolution, specific patient preparation, and the intravenous injection of contrast agent, allowing for the visualization of calcified and non-calcified atherosclerotic plaque 3.

Detection and Quantification of Atherosclerosis

• CT with IV contrast can detect and quantify subclinical coronary atherosclerosis even in asymptomatic individuals, with a large body of evidence attesting to its high predictive value for future cardiac events 3.
• The detection of coronary artery calcium (CAC) is relatively straightforward and is applied to detect and quantify subclinical coronary atherosclerosis 3.
• Studies have shown that identifying atherosclerosis on CT angiography can impact outcomes, with a lower death rate and improved event-free survival in patients who underwent CTA compared to those who underwent standard of care 4.

Comparison with Other Imaging Modalities

• Other imaging modalities, such as magnetic resonance imaging (MRI) and positron emission tomography (PET), are also available for the assessment of atherosclerotic burden and potential prediction of future events 5.
• MRI has emerged as a leading noninvasive imaging modality for atherosclerotic disease, with the ability to differentiate the major components of atherosclerotic plaque and image the vessel wall 6.
• The integration of different imaging techniques in clinical practice may allow for superior risk stratification and therapeutic planning, as well as monitoring of interventional and medication-based treatment strategies 5.