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

Indications for CT Chest Scan

CT chest scan is indicated for detecting chest trauma injuries, evaluating suspected pulmonary metastases, assessing pulmonary parenchymal disease, and investigating mediastinal abnormalities that cannot be adequately characterized by chest radiography.

Trauma Evaluation

• CT chest with IV contrast is the preferred imaging for suspected chest trauma as it can detect most injuries including rib fractures, pneumothorax, hemothorax, and pulmonary contusion with higher sensitivity and specificity than conventional radiographs 1
• In patients with blunt chest trauma, CT can identify potentially life-threatening injuries missed on initial chest radiographs, including aortic lacerations, pleural effusions, and pericardial effusions 2
• Over 50% of patients with normal initial chest radiographs after blunt trauma may show multiple injuries on CT scan, including potentially fatal aortic lesions 2
• For major blunt trauma, whole-body CT may be warranted, especially for high-velocity (>35 mph) motor vehicle collisions, rollover accidents, motorcycle trauma, and falls from >15 feet 1

Pulmonary Disease Assessment

• CT chest without IV contrast is considered useful for evaluating airways, pulmonary parenchyma, and interstitium in patients with dyspnea or suspected diffuse lung disease 1
• For chronic cough evaluation, CT chest is recommended when more common causes are excluded or empirically treated, typically preceded by a chest radiograph 1
• CT chest is superior to chest radiography for determining the type, extent, and distribution of emphysema and bronchial wall abnormalities in COPD patients 1
• For suspected pleural effusion, CT chest with IV contrast can accurately characterize the effusion and identify underlying causes, particularly when malignancy is suspected 1

Cancer Staging and Surveillance

• CT chest is far more sensitive than chest radiography for detecting pulmonary metastatic disease, with chest radiography having sensitivity as low as 28% compared to CT 1
• For head and neck cancer patients, CT chest is recommended for detecting pulmonary metastases, which are common sites of distant spread 1
• CT chest confers superior spatial localization and contrast resolution compared to radiography, allowing for detection of small pulmonary nodules that may represent early metastatic disease 1
• In patients with heavy smoking history and head and neck cancer, CT chest is indicated for both cancer surveillance and screening for primary lung cancer 1

Cardiovascular Assessment

• CT chest with IV contrast can evaluate suspected cardiac injury following blunt chest trauma, detecting conditions such as cardiac chamber rupture, pericardial rupture, and myocardial infarction 1
• For suspected heart failure of undetermined etiology, CT chest has limited value as initial imaging but may help evaluate extracoronary and extracardiac findings, such as pericardial thickening or calcification 1
• Coronary CT angiography is highly effective for identifying coronary anomalies such as myocardial bridges 3
• CT chest with IV contrast is recommended for evaluating paratracheal abnormalities, as it helps distinguish nodes from mediastinal vessels 4

Protocol Considerations

• For mediastinal evaluation, CT chest with IV contrast is preferred as it improves detection of mediastinal and hilar adenopathy by distinguishing nodes from mediastinal vessels 4
• Thin-section CT (1.5 mm contiguous sections) is recommended for optimal characterization of pulmonary and mediastinal abnormalities 4
• CT chest without IV contrast may be considered as an alternative in patients with contraindications to IV contrast, though it provides less optimal evaluation of mediastinal structures 4
• For trauma patients, contrast-enhanced CT of the chest is the preferred imaging workup of suspected chest trauma regardless of contrast administration 1

Common Pitfalls to Avoid

• Relying solely on chest radiography for trauma evaluation may miss significant injuries, as CT is more sensitive and specific 1
• Using non-contrast CT for mediastinal evaluation may lead to inadequate assessment of the relationship between vascular structures and lymph nodes 4
• Failing to obtain thin-section images may result in missing small nodules or inadequate characterization of abnormalities 4
• Performing CT chest indiscriminately for all patients with chronic cough may yield low clinical value; appropriate patient selection improves the specificity of findings 1