Should a computed tomography (CT) scan for lung nodules be performed with or without contrast?

From the Guidelines

For evaluating lung nodules, a non-contrast CT scan is typically recommended as the initial imaging study. Non-contrast CT scans provide excellent visualization of lung nodules without the need for intravenous contrast material. The natural contrast between air-filled lungs and solid nodules allows for clear identification of nodule characteristics including size, shape, margins, and density. Contrast is generally not necessary for routine lung nodule evaluation and follow-up as it doesn't significantly improve nodule detection or characterization in most cases, as supported by the American College of Radiology guidelines 1.

Key Points to Consider

• The use of non-contrast CT scans minimizes radiation exposure, which is beneficial for patients who may need multiple follow-up scans for nodule surveillance.
• Certain nodule characteristics suggestive of benign etiology, such as diffuse, central, laminated, or popcorn calcifications patterns, are better appreciated by CT and can avoid additional workup 1.
• Multiple imaging features that increase the risk of malignancy are best characterized on CT, including nodule size, morphology, location, multiplicity, and the presence of emphysema or fibrosis.
• However, contrast-enhanced CT may be appropriate in specific situations, such as when there is concern for mediastinal invasion, when evaluating for hilar or mediastinal lymphadenopathy, or when assessing for vascular involvement, as noted in the guidelines 1.

Decision Making

The decision to use contrast should be made on an individual basis, considering the clinical context and the specific diagnostic questions that need to be answered. Guidelines emphasize clinicians should discuss risks and benefits of management strategies with patients and incorporate their preferences 1.

Evidence Summary

The evidence from recent studies 1 supports the use of non-contrast CT scans as the initial imaging study for evaluating lung nodules, with contrast-enhanced CT reserved for specific situations. This approach prioritizes minimizing radiation exposure while ensuring accurate characterization of lung nodules, ultimately impacting morbidity, mortality, and quality of life.

From the FDA Drug Label

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.

The decision to use contrast in a CT scan for lung nodules should be based on a careful evaluation of the individual patient's clinical and radiological findings.

• Key considerations include the potential benefits of contrast enhancement, such as improved diagnostic assessment of tumors and other lesions, versus the associated risks and increased radiation exposure.
• Contrast enhancement may be useful in distinguishing between vascularized and non-vascularized lesions, but unenhanced scanning may provide adequate diagnostic information in some cases 2.

From the Research

Lung Nodules CT Scan

• A CT scan with contrast is often used to assess solitary pulmonary nodules (SPNs) 3
• The use of contrast can help distinguish between malignant and benign nodules by providing information on the degree and pattern of enhancement 3
• Dual-energy CT scans can provide both virtual nonenhanced and iodine-enhanced images from a single scan, reducing radiation exposure and measurement error 3

Non-Contrast CT Scan

• A nonenhanced scan is used to detect calcification in the SPN or lymph node, which is an important determinant of benignity 3
• Small nodules are more likely to be benign, and the probability of malignancy is less than 1% for all nodules smaller than 6 mm 4

Dynamic Contrast-Enhanced CT

• Dynamic contrast-enhanced CT (DCE-CT) is a functional test that involves the acquisition of a dynamic series of images of a nodule before and following the administration of intravenous iodinated contrast medium 5
• DCE-CT can help characterize nodules and distinguish between benign and malignant lesions 6, 5
• The use of DCE-CT can provide additional information on the pharmacokinetic background of contrast-enhanced CT and MRI, improving diagnostic performance 6