What are the indications for a chest CT (computed tomography) with contrast?

From the Guidelines

Chest CT with contrast is indicated for evaluating suspected tracheal or bronchial stenosis, pulmonary embolism, aortic dissection or aneurysm, mediastinal masses, hilar lymphadenopathy, and staging or follow-up of certain malignancies, as it provides optimal evaluation of enhancement characteristics and hilar and mediastinal adenopathy 1. The use of intravenous contrast medium enhances visualization of vascular structures and improves tissue characterization by highlighting differences in vascularity. Some key points to consider when ordering a chest CT with contrast include:

• Assessing renal function (eGFR >30 mL/min/1.73m² is generally acceptable) 1
• Checking for contrast allergies
• Considering pregnancy status
• Fasting for 4-6 hours before the scan, but allowing medications with small sips of water
• Potential contraindications include severe renal impairment, previous severe contrast reaction, and untreated hyperthyroidism The most recent and highest quality study, published in 2024, recommends the use of chest CT with IV contrast for evaluating central airway pathology, such as masses, thickening, and stenosis 1. Additionally, a 2023 study suggests that CT chest with IV contrast can accurately identify pulmonary metastasis and be used to detect thoracic nodal and skeletal metastases to ribs or vertebrae 1. However, it is essential to prioritize the most recent and highest quality study, which is the 2024 study 1. In terms of specific indications, chest CT with contrast is particularly useful for evaluating suspected tracheal or bronchial stenosis, as it allows for the assessment of the location, shape, dimensions, mural extent, and attenuation characteristics of tumors of the large airways 1. It is also useful for detecting intrathoracic disease in cases of malignancy and for assessing the degree of stenosis, extraluminal involvement of lesions, and extension to adjacent structures 1. Overall, the use of chest CT with contrast is a valuable diagnostic tool for evaluating a range of thoracic conditions, and its indications should be guided by the most recent and highest quality evidence 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 For example, a cyst may be distinguished from a vascularized solid lesion when precontrast and enhanced scans are compared; the nonperfused mass shows unchanged x-ray absorption (CT number) 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

The indications for a chest CT with contrast include:

• Diagnostic assessment of tumor
• Evaluation of abscess
• Distinguishing cysts from vascularized solid lesions
• Characterization of vascularized lesions, which may be malignant, benign, or normal tissue 2

From the Research

Indications for Chest CT with Contrast

The following are indications for a chest CT with contrast:

• Diagnosis of pulmonary embolism (PE) 3, 4, 5
• Evaluation of acute chest pain 3, 5
• Assessment of aortic dissection 3, 6
• Staging and follow-up of lung cancer and other thoracic malignancies 7
• Evaluation of pleural and pulmonary lesions 7
• Diagnosis of other conditions such as pneumonia, abscesses, and empyema 7

Specific Conditions

• Pulmonary embolism: Chest CT with contrast is the preferred imaging modality for diagnosing PE, especially in patients with acute chest pain and shortness of breath 3, 4, 5
• Aortic dissection: Chest CT with contrast is used to evaluate the extent of the dissection and to plan treatment 3, 6
• Lung cancer: Chest CT with contrast is used for staging and follow-up of lung cancer, as well as for evaluating pleural and pulmonary lesions 7

Contrast Timing

• Venous-phase CT (60-second phase) is preferred over arterial-phase CT for evaluating pulmonary embolism, pleural and pulmonary lesions, and nodal assessment 7
• The use of contrast-enhanced chest CT can help diagnose unsuspected pulmonary embolism, with adequate enhancement defined as 200 Hounsfield units (HU) or greater 4