Chest Imaging

Medical School · Year 4 · Radiology · includes a quiz and discussion video

Chest Imaging

Year 4: Radiology Elective

Learning Objectives

By the end of this seminar, students will be able to:

Apply a systematic approach to chest radiograph interpretation including assessment of technical quality, normal anatomy, and pathologic findings
Identify and characterize pulmonary opacities including consolidation, interstitial patterns, atelectasis, and nodules on chest radiography and CT
Recognize pleural abnormalities including effusion, pneumothorax, and pleural thickening and select appropriate imaging for further evaluation
Evaluate cardiac silhouette and mediastinal structures for evidence of cardiomegaly, chamber enlargement, heart failure, and mediastinal masses
Apply CT chest protocols appropriately for pulmonary embolism, interstitial lung disease, and pulmonary nodule characterization
Communicate critical chest imaging findings effectively and understand the importance of structured reporting and recommendation tracking

I. Systematic Chest X-Ray Approach

Technical quality assessment forms the foundation of accurate chest radiograph interpretation and must be performed before evaluating for pathology. Rotation is assessed by comparing the medial ends of the clavicles to the spinous process, which should be equidistant on a properly positioned frontal radiograph. Adequate inspiration is confirmed by counting posterior ribs visible above the diaphragm, with eight to ten ribs indicating sufficient lung expansion. Penetration should allow visualization of the thoracic spine through the cardiac silhouette while maintaining soft tissue detail, and patient position should be noted as posteroanterior or anteroposterior because the latter magnifies the cardiac silhouette.

The ABCDE approach provides a memorable framework for systematic chest radiograph review that ensures no structures are overlooked. Airway evaluation includes assessment of tracheal position, which should be midline or slightly right of midline, and patency of the major bronchi. Bones and soft tissues are examined for fractures, lytic lesions, and subcutaneous emphysema. Cardiac silhouette size and contour are evaluated along with the mediastinal structures. The diaphragm and subdiaphragmatic regions are assessed for free air, herniation, and masses, followed by examination of everything else including lung parenchyma and pleural surfaces.

Normal chest radiograph anatomy demonstrates consistent relationships that serve as references for detecting abnormalities. The trachea is visible as a midline air column that bifurcates at the carina around the level of the fourth or fifth thoracic vertebra. The hila contain the major pulmonary vessels and bronchi, with the left hilum positioned slightly higher than the right in most patients. The cardiac silhouette on a posteroanterior radiograph should measure less than half the thoracic width at its widest point, and the costophrenic angles should be sharp and well-defined.

Comparison with prior imaging studies dramatically improves detection of subtle abnormalities and provides essential context for interpreting new findings. Even small nodules or areas of scarring become clinically significant if they represent interval change from previous examinations. Comparison should ideally be made with studies of similar technique, as differences between posteroanterior and anteroposterior positioning or between inspiration and expiration can simulate pathology. Documentation of comparison studies and explicit statement of interval changes or stability forms an essential component of the radiograph interpretation.

<image>Panel A: Posteroanterior chest radiograph with annotations demonstrating normal anatomic landmarks including trachea, carina, hila, and cardiac silhouette. Panel B: Properly positioned radiograph showing symmetric clavicular heads and adequate inspiration. Panel C: Under-penetrated radiograph with obscured spine compared to appropriately exposed examination. Panel D: Side-by-side comparison demonstrating interval development of a right upper lobe opacity.</image>

II. Pulmonary Opacities

Consolidation represents replacement of alveolar air by fluid, cells, or other material and produces a characteristic radiographic pattern. The hallmark of consolidation is the air bronchogram, which appears as branching lucent structures within an area of opacification representing air-filled bronchi surrounded by airless alveoli. Consolidation typically respects lobar boundaries because the visceral pleura limits spread of disease, and the silhouette sign helps localize the process to specific lobes based on which normal borders are obscured. Common causes of consolidation include bacterial pneumonia, pulmonary edema, pulmonary hemorrhage, and aspiration.

Interstitial lung disease produces patterns distinct from alveolar consolidation, reflecting abnormalities of the pulmonary interstitium rather than airspace filling. Reticular patterns appear as a network of lines representing thickened interlobular septa and intralobular interstitium. Nodular patterns consist of small discrete opacities that may be distributed randomly, along lymphatic pathways, or in a centrilobular distribution. Ground glass opacity appears as hazy increased lung density through which vessels and bronchi remain visible, distinguishing it from consolidation where these structures are obscured.

Atelectasis describes loss of lung volume resulting from alveolar collapse and produces characteristic radiographic findings depending on the mechanism and extent. Obstructive atelectasis occurs when an endobronchial lesion prevents air from reaching distal lung segments, which then collapse. Compressive atelectasis results from external pressure on lung tissue by pleural effusion, pneumothorax, or mass. Radiographic signs of volume loss include displacement of fissures, elevation of the hemidiaphragm, mediastinal shift toward the atelectatic lung, and compensatory hyperinflation of adjacent lung segments.

Pulmonary nodules and masses require characterization to determine the likelihood of malignancy and appropriate management. Nodule size represents the most important predictor of malignancy, with larger nodules carrying higher risk. Margins should be evaluated for smoothness, lobulation, or spiculation, with irregular spiculated margins raising concern for malignancy. Calcification patterns can suggest benign etiology, with central, popcorn, and laminated calcifications favoring granuloma or hamartoma. Stability over two years on serial imaging suggests benign etiology, while growth mandates further evaluation with biopsy or resection.

<image>Panel A: Chest radiograph showing right lower lobe consolidation with air bronchograms and obscured right hemidiaphragm. Panel B: High-resolution CT demonstrating reticular pattern with peripheral and basal predominance consistent with usual interstitial pneumonia. Panel C: Chest radiograph showing complete left upper lobe atelectasis with elevated left hemidiaphragm and mediastinal shift. Panel D: CT showing a spiculated right upper lobe nodule highly suspicious for primary lung malignancy.</image>

III. Pleural Abnormalities

Pleural effusion appears on chest radiography as dependent opacification that blunts the normally sharp costophrenic angles. The classic appearance includes a meniscus sign, a concave upward curving of the fluid surface against the chest wall that results from capillary action between the pleural layers. Small effusions may only be visible on lateral radiographs where they collect in the posterior costophrenic sulcus, the most dependent portion of the thorax in upright patients. Lateral decubitus positioning allows detection of layering fluid that would otherwise be obscured by overlying lung and helps determine whether an effusion is free-flowing or loculated.

Pneumothorax presents as a visible visceral pleural line separated from the chest wall by a lucent space devoid of lung markings. On upright radiographs, air rises to the apex and is best visualized on expiratory imaging that accentuates the contrast between collapsed lung and surrounding air. In supine patients such as those in intensive care units, pneumothorax may present as the deep sulcus sign, an abnormally deep and lucent lateral costophrenic angle. Tension pneumothorax represents a life-threatening emergency and is suggested by mediastinal shift away from the affected side, flattening or inversion of the hemidiaphragm, and hemodynamic compromise.

Pleural thickening may result from prior infection, inflammation, asbestos exposure, or malignancy and appears as soft tissue density along the pleural surface. Calcified pleural plaques are highly specific for prior asbestos exposure and typically appear as bilateral, often discontinuous areas of calcification along the parietal pleura. Diffuse pleural thickening involving the visceral pleura may restrict lung expansion and cause restrictive ventilatory impairment. Malignant pleural disease, including mesothelioma and metastatic disease, produces nodular or mass-like thickening that may encase the lung.

Computed tomography provides superior evaluation of pleural disease compared to radiography, enabling distinction between pleural and parenchymal processes and characterization of pleural fluid. CT can differentiate transudative effusions, which appear as simple fluid, from exudative effusions, which may demonstrate higher attenuation, septations, or enhancement. The split pleura sign, enhancement of both visceral and parietal pleura separated by fluid, suggests empyema. CT also detects occult pneumothorax that may be invisible on supine radiographs and is essential for evaluating trauma patients and those with complex pleural disease.

<image>Panel A: Chest radiograph showing large left pleural effusion with meniscus sign and complete opacification of the left hemithorax. Panel B: Upright chest radiograph demonstrating right apical pneumothorax with visible visceral pleural line. Panel C: CT showing calcified pleural plaques bilaterally in a patient with asbestos exposure history. Panel D: CT with contrast demonstrating split pleura sign with enhancing thickened pleural layers surrounding an empyema.</image>

IV. Cardiac Imaging

Cardiac size assessment on chest radiography relies on the cardiothoracic ratio, calculated by dividing the maximum transverse cardiac diameter by the maximum internal thoracic width at the level of the diaphragm. A ratio exceeding fifty percent on a posteroanterior radiograph suggests cardiomegaly, though this measurement is unreliable on anteroposterior films where magnification artificially enlarges the cardiac silhouette. Global cardiomegaly should prompt consideration of dilated cardiomyopathy, pericardial effusion, and multivalvular disease. Pericardial effusion produces a characteristic water-bottle configuration with a globular, smooth cardiac contour.

Individual chamber enlargement produces characteristic changes in cardiac contour and adjacent structures that can be appreciated on chest radiography. Left atrial enlargement causes a double density overlying the right cardiac border, elevation of the left main bronchus, and posterior displacement of the esophagus visible on lateral films. Left ventricular enlargement displaces the cardiac apex inferiorly and laterally beyond the mid-clavicular line. Right atrial enlargement increases the convexity of the right heart border, while right ventricular enlargement fills the retrosternal space on lateral radiographs and may elevate the cardiac apex.

Pulmonary vascular patterns on chest radiography provide information about pulmonary hemodynamics and cardiac function. Normal pulmonary vasculature demonstrates larger vessels in the lower lobes due to gravitational effects on blood flow. Cephalization, or redistribution of blood flow to the upper lobes, represents an early sign of elevated left atrial pressure and incipient heart failure. Pulmonary arterial hypertension causes enlargement of the central pulmonary arteries with rapid tapering of peripheral vessels, the so-called pruned tree appearance. Asymmetric pulmonary vascularity may indicate pulmonary embolism with oligemia in the affected territory or unilateral parenchymal disease.

The radiographic progression of congestive heart failure follows a predictable sequence that correlates with left atrial and pulmonary venous pressure elevation. Early heart failure produces cephalization and cardiomegaly without significant parenchymal abnormality. Moderate heart failure adds interstitial edema manifested as Kerley B lines, short horizontal lines at the lung bases representing thickened interlobular septa, and peribronchial cuffing. Severe heart failure produces alveolar edema with bilateral airspace opacities classically described as a bat-wing or butterfly pattern emanating from the hila, often accompanied by pleural effusions.

<image>Panel A: Chest radiograph demonstrating marked cardiomegaly with cardiothoracic ratio exceeding fifty percent. Panel B: Double density sign of left atrial enlargement visible through the right cardiac silhouette. Panel C: Chest radiograph showing cephalization with upper lobe vessel prominence indicating early heart failure. Panel D: Bilateral perihilar bat-wing opacities of pulmonary edema with Kerley B lines at the lung bases.</image>

V. Mediastinal Abnormalities

The mediastinum is conventionally divided into anterior, middle, and posterior compartments, with characteristic pathology arising in each location. The anterior mediastinum extends from the sternum to the pericardium and great vessels and contains the thymus, lymph nodes, and fat. The middle mediastinum contains the heart, pericardium, great vessels, trachea, and esophagus. The posterior mediastinum includes the paravertebral regions containing neural structures and the descending aorta. Localization of a mediastinal mass to a specific compartment substantially narrows the differential diagnosis.

Anterior mediastinal masses are remembered by the mnemonic of the terrible T's: thymic neoplasms, teratoma and other germ cell tumors, thyroid masses, and terrible lymphoma. Thymomas appear as smooth or lobulated masses in the prevascular space and may be associated with myasthenia gravis. Lymphoma, particularly Hodgkin disease, commonly presents with anterior mediastinal and hilar adenopathy in young adults. Substernal thyroid extension from goiter presents as a mass that rises from the thoracic inlet and moves with swallowing. Germ cell tumors including teratoma and seminoma occur predominantly in young males.

Hilar abnormalities may represent lymphadenopathy, vascular structures, or bronchogenic lesions and require careful evaluation to distinguish from normal variants. Unilateral hilar enlargement raises concern for bronchogenic carcinoma with hilar lymph node involvement or, less commonly, primary hilar malignancy. Bilateral hilar enlargement suggests systemic disease including sarcoidosis, which classically produces bilateral symmetric hilar adenopathy, lymphoma, or infectious diseases such as histoplasmosis. The hilar overlay sign, in which hilar vessels are visible through a mass, indicates that the abnormality lies anterior or posterior to the hilum rather than within it.

Aortic abnormalities visible on chest radiography include aneurysm, dissection, and traumatic injury. A widened mediastinum greater than eight centimeters on a supine anteroposterior radiograph raises concern for acute aortic pathology and requires urgent evaluation. Aortic unfolding, a widened and tortuous aortic contour, commonly results from hypertension and atherosclerosis in elderly patients. Aortic calcification in the wall of the ascending aorta or arch may be displaced inward by acute intramural hematoma or dissection. CT angiography provides definitive evaluation of suspected acute aortic syndrome and is essential for surgical planning.

<image>Panel A: Chest radiograph showing anterior mediastinal mass representing thymoma with smooth borders. Panel B: CT demonstrating bilateral hilar and mediastinal lymphadenopathy in sarcoidosis. Panel C: Chest radiograph with widened mediastinum suspicious for acute aortic pathology in a trauma patient. Panel D: CT angiography revealing aortic dissection with intimal flap separating true and false lumens.</image>

VI. CT Chest Protocols

Non-contrast CT of the chest serves as the primary modality for evaluating pulmonary parenchymal abnormalities including nodules, interstitial lung disease, and emphysema. Lung cancer screening utilizes low-dose technique to minimize radiation exposure while maintaining sensitivity for detection of small pulmonary nodules. Pulmonary nodule follow-up protocols enable accurate measurement of nodule size and assessment of growth over time. COVID-19 and other viral pneumonias demonstrate characteristic patterns on non-contrast CT including ground glass opacity, consolidation, and crazy paving pattern.

CT pulmonary angiography requires precise timing of intravenous contrast injection to maximize opacification of the pulmonary arteries during image acquisition. The examination is triggered when contrast density in the main pulmonary artery reaches a predetermined threshold, ensuring optimal visualization of emboli. Findings diagnostic of pulmonary embolism include intraluminal filling defects within opacified pulmonary arteries, which may be central, eccentric, or occlusive. Secondary signs including right ventricular enlargement, reflux of contrast into the hepatic veins, and peripheral wedge-shaped infarcts provide additional diagnostic and prognostic information.

High-resolution CT employs thin-slice technique, typically one to two millimeters, to optimize visualization of pulmonary parenchymal detail for evaluation of interstitial lung disease. Images acquired with the patient prone help distinguish dependent atelectasis from true posterior lung abnormality. Expiratory imaging detects air trapping as geographic areas of decreased attenuation that fail to increase in density during expiration. The combination of inspiratory and expiratory prone and supine imaging provides comprehensive assessment of interstitial and small airways disease patterns.

Contrast phase and timing determine which vascular structures are optimally evaluated on CT examination. Non-contrast imaging best demonstrates calcification and native lung parenchyma without obscuring artifact from contrast. Arterial phase imaging acquired during peak pulmonary arterial enhancement is optimal for pulmonary embolism evaluation. Delayed imaging may be added to arterial phase for aortic dissection evaluation to assess for continued false lumen opacification. Triple rule-out protocols evaluate for pulmonary embolism, aortic dissection, and coronary artery disease simultaneously but require higher radiation doses and contrast volumes.

<image>Panel A: Low-dose screening CT demonstrating a small solid pulmonary nodule requiring follow-up. Panel B: CT pulmonary angiography showing saddle embolus straddling the main pulmonary artery bifurcation. Panel C: High-resolution CT in prone position showing basal predominant honeycombing of usual interstitial pneumonia. Panel D: Expiratory CT demonstrating mosaic attenuation pattern with geographic areas of air trapping.</image>

VII. Common Emergency Findings

Community-acquired pneumonia demonstrates variable radiographic patterns that may suggest the causative organism and guide empirical antimicrobial therapy. Lobar consolidation affecting a single pulmonary segment or lobe with air bronchograms suggests typical bacterial pneumonia, classically Streptococcus pneumoniae. Bronchopneumonia produces multifocal patchy airspace opacities that may be bilateral and is associated with Staphylococcus aureus and gram-negative organisms. Interstitial patterns with bilateral reticular or reticulonodular opacities suggest atypical pathogens including Mycoplasma, Chlamydia, and viruses. Cavitary pneumonia raises concern for anaerobic infection, tuberculosis, or fungal disease.

Pulmonary embolism represents a potentially life-threatening emergency that requires rapid diagnosis and treatment to prevent morbidity and mortality. CT pulmonary angiography findings include intraluminal filling defects within contrast-opacified pulmonary arteries, which may be partial or complete. Right ventricular strain suggested by right ventricular to left ventricular diameter ratio greater than one indicates hemodynamically significant embolism with increased risk of adverse outcomes. Reflux of contrast into the inferior vena cava and hepatic veins indicates elevated right-sided pressures. Hampton hump, a peripheral wedge-shaped consolidation representing pulmonary infarction, develops in a minority of patients but is highly suggestive of pulmonary embolism when present.

Acute aortic dissection presents with severe chest pain and requires emergent imaging to confirm diagnosis and guide management decisions. CT angiography demonstrates an intimal flap separating the true and false lumens, with the true lumen typically remaining opacified throughout cardiac cycle phases. Stanford classification divides dissection into Type A involving the ascending aorta, which requires emergent surgical repair, and Type B involving only the descending aorta. Complications including malperfusion of branch vessels, pericardial effusion suggesting rupture, and involvement of the coronary ostia must be evaluated. Intramural hematoma, a variant of acute aortic syndrome, appears as crescentic high-attenuation thickening of the aortic wall without intimal flap.

Thoracic trauma evaluation with CT detects injuries that may be occult on chest radiography and provides comprehensive assessment of multiple potential pathologies. Pneumothorax may be entirely invisible on supine portable radiographs but is readily detected on CT, with occult pneumothorax identified in up to fifteen percent of trauma patients. Hemothorax appears as dependent high-attenuation pleural fluid and may indicate ongoing hemorrhage requiring intervention. Pulmonary contusion manifests as patchy airspace opacity that typically develops within six hours of trauma and does not respect lobar boundaries. Rib fractures, while often visible on radiography, are better characterized on CT, which also detects associated sternal and thoracic spine injuries.

<image>Panel A: Chest radiograph showing right lower lobe consolidation with air bronchograms consistent with community-acquired pneumonia. Panel B: CT pulmonary angiography demonstrating large bilateral pulmonary emboli with right ventricular enlargement. Panel C: CT angiography showing Type A aortic dissection with intimal flap extending into the arch. Panel D: CT in trauma patient showing right pneumothorax, pulmonary contusion, and multiple rib fractures.</image>

VIII. Pulmonary Nodules

Management of incidentally detected pulmonary nodules follows evidence-based guidelines that balance cancer detection against the harms of unnecessary procedures and radiation exposure from serial imaging. The Fleischner Society guidelines stratify nodule management based on size, morphology, and patient risk factors for lung cancer. Nodules smaller than six millimeters in patients without risk factors generally require no follow-up due to the very low probability of malignancy. Larger nodules and those in high-risk patients require surveillance imaging at intervals determined by nodule characteristics, with growth or development of suspicious features prompting biopsy or resection.

Lung cancer screening with low-dose CT has been demonstrated to reduce lung cancer mortality in high-risk populations and is recommended for eligible individuals. Current criteria include age fifty to eighty years, smoking history of at least twenty pack-years, and current smoking or cessation within the past fifteen years. Annual low-dose CT screening enables detection of early-stage lung cancers when curative treatment is most effective. Screening programs must include robust systems for nodule tracking, false positive management, and smoking cessation counseling to optimize benefit and minimize harm.

Nodule characterization on CT provides information that helps distinguish benign from potentially malignant lesions. Size is measured as the average of long and short axis diameters and represents the most important predictor of malignancy risk. Solid nodules are entirely soft tissue attenuation, ground glass nodules are hazy without obscuring underlying structures, and part-solid nodules contain both components. Margin characteristics including smooth, lobulated, and spiculated contours influence management, with spiculation raising the highest suspicion for malignancy. Upper lobe location is associated with higher malignancy risk compared to lower lobe nodules of equivalent size.

Lung-RADS provides a standardized reporting system for lung cancer screening CT that categorizes findings and recommends management actions. Category one indicates a negative examination without pulmonary nodules or with definitely benign findings. Category two includes benign-appearing nodules that require continued annual screening but no short-interval follow-up. Category three represents probably benign findings that warrant six-month follow-up imaging. Category four indicates suspicious findings that may require short-interval follow-up, PET imaging, tissue sampling, or consultation with a multidisciplinary team depending on the specific subcategory.

<image>Panel A: Comparison CT images demonstrating growth of a pulmonary nodule over twelve months, concerning for malignancy. Panel B: Chart showing Fleischner Society nodule management recommendations based on size and risk factors. Panel C: Spiculated solid nodule in the right upper lobe with characteristics highly suspicious for primary lung malignancy. Panel D: Part-solid nodule with both ground glass and solid components requiring careful characterization and follow-up.</image>

IX. Interstitial Lung Disease

High-resolution CT pattern recognition forms the foundation of imaging evaluation for interstitial lung disease and enables categorization that guides diagnosis and management. Usual interstitial pneumonia pattern demonstrates basal-predominant and peripheral-predominant reticulation with honeycombing, traction bronchiectasis, and minimal ground glass opacity. Nonspecific interstitial pneumonia pattern shows bilateral ground glass opacity and reticulation with relative sparing of the immediate subpleural region. Organizing pneumonia pattern features peripheral and peribronchovascular consolidation that may be migratory over time. Hypersensitivity pneumonitis demonstrates centrilobular nodules, mosaic attenuation, and upper to mid lung predominance.

The usual interstitial pneumonia pattern strongly suggests underlying idiopathic pulmonary fibrosis when present in the appropriate clinical context without identifiable cause. Honeycombing, defined as clustered thick-walled cystic spaces typically measuring three to ten millimeters, represents established fibrosis and is the most specific finding. Traction bronchiectasis and bronchiolectasis indicate distortion of airways by surrounding fibrosis. The combination of honeycombing, traction bronchiectasis, and basal and peripheral predominance without features suggesting alternative diagnoses is diagnostic of usual interstitial pneumonia pattern without need for surgical lung biopsy.

Distribution of interstitial abnormalities on high-resolution CT provides important diagnostic information that helps narrow the differential diagnosis. Upper lobe predominance characterizes sarcoidosis, hypersensitivity pneumonitis, silicosis, and coal worker's pneumoconiosis. Lower lobe predominance typifies usual interstitial pneumonia pattern, nonspecific interstitial pneumonia, and asbestosis. Peripheral predominance suggests usual interstitial pneumonia, chronic eosinophilic pneumonia, and organizing pneumonia. Central or peribronchovascular distribution is seen in sarcoidosis and lymphangitic carcinomatosis.

Acute exacerbation of interstitial lung disease presents with clinical deterioration and new imaging findings superimposed on the underlying chronic pattern. New ground glass opacity or consolidation beyond the expected extent of baseline disease suggests acute exacerbation and carries a poor prognosis. Alternative diagnoses including infection, heart failure, and pulmonary embolism must be excluded before attributing deterioration to disease exacerbation. Patients with underlying usual interstitial pneumonia are at greatest risk for acute exacerbation, though the complication can occur with other interstitial lung diseases.

<image>Panel A: High-resolution CT showing honeycombing and traction bronchiectasis at the lung bases diagnostic of usual interstitial pneumonia. Panel B: Bilateral ground glass opacity with subpleural sparing characteristic of nonspecific interstitial pneumonia. Panel C: Peripheral consolidation in organizing pneumonia with reversed halo sign. Panel D: Centrilobular nodules and mosaic attenuation in hypersensitivity pneumonitis.</image>

X. Reporting and Communication

Structured chest imaging reports follow a standardized format that facilitates clear communication between radiologists and referring clinicians. The clinical history section documents the indication for the examination and relevant patient information that may influence interpretation. The technique section describes the imaging protocol, contrast administration, and any factors limiting image quality. The findings section systematically describes observations organized by anatomic region or pathologic significance. The impression provides a concise summary of key diagnoses and conclusions that directly addresses the clinical question.

Critical findings require immediate verbal communication to the responsible provider to enable timely intervention that may be life-saving. Tension pneumothorax with mediastinal shift demands immediate notification because decompression can be performed at the bedside. Massive pulmonary embolism with hemodynamic compromise warrants urgent communication to facilitate anticoagulation and consideration of thrombolysis or thrombectomy. Aortic dissection involving the ascending aorta requires emergent surgical consultation. Free air suggesting hollow viscus perforation necessitates prompt surgical evaluation.

Recommendations appended to imaging reports provide guidance for additional imaging, clinical correlation, or follow-up that should be tracked to ensure appropriate action. Incidental nodule findings require clear documentation of recommended follow-up interval based on size and risk stratification. Indeterminate findings may warrant additional imaging with different modalities such as PET for metabolic characterization of pulmonary nodules. Specialty referral recommendations, such as pulmonology consultation for suspected interstitial lung disease, should be explicit and actionable.

Common interpretation pitfalls can be avoided through systematic approach and awareness of potential errors. Small apical pneumothoraces may be overlooked if the lung apices are not specifically evaluated on every chest radiograph. Retrocardiac and retrodiaphragmatic opacities are easily missed if lateral views are not obtained or carefully reviewed. Confirmation bias leads interpreters to stop searching after finding one abnormality, potentially missing additional significant findings. Comparison with prior imaging should always be performed when available to detect subtle interval changes that might otherwise escape detection.

<image>Panel A: Example of a well-structured chest CT report with clearly organized sections and actionable impression. Panel B: Critical finding notification documentation template for tension pneumothorax. Panel C: Nodule tracking system showing recommended follow-up intervals and completion status. Panel D: Side-by-side comparison images demonstrating a subtle new nodule that would be missed without prior study comparison.</image>

Summary

Systematic chest radiograph interpretation using the ABCDE approach ensures comprehensive evaluation of airway, bones, cardiac silhouette, diaphragm, and lung parenchyma while always comparing to prior studies. Technical quality assessment including rotation, inspiration, and penetration must be performed before interpreting findings. Pulmonary opacities are categorized as consolidation with air bronchograms, interstitial patterns, atelectasis with volume loss, or nodules and masses requiring characterization. Pleural abnormalities include effusion with meniscus sign, pneumothorax with visible visceral pleural line, and pleural thickening from various causes.

Cardiac imaging assesses cardiothoracic ratio, individual chamber enlargement patterns, pulmonary vascular distribution, and the progressive findings of congestive heart failure. Mediastinal masses are localized to anterior, middle, or posterior compartments to narrow differential diagnosis, with the four T's characterizing anterior mediastinal pathology. CT protocols are tailored to clinical indication, with non-contrast for nodules and interstitial disease, CT pulmonary angiography for embolism, and high-resolution technique for parenchymal detail.

Emergency chest imaging identifies pneumonia patterns, pulmonary embolism with filling defects and right heart strain, aortic dissection with intimal flap, and traumatic injuries including occult pneumothorax. Pulmonary nodule management follows Fleischner Society guidelines based on size and risk factors, while lung cancer screening with low-dose CT reduces mortality in eligible high-risk populations. Interstitial lung disease patterns including usual interstitial pneumonia, nonspecific interstitial pneumonia, and hypersensitivity pneumonitis are recognized by characteristic high-resolution CT findings.

Structured reporting with clear technique, findings, and impression sections facilitates clinical communication. Critical findings require immediate verbal notification to enable timely intervention. Recommendations for follow-up imaging and clinical action must be tracked to ensure completion and appropriate management of identified abnormalities.

Key Terms

Air Bronchogram: Visualization of air-filled bronchi as branching lucencies within consolidated lung parenchyma, indicating that the airway is patent and the opacity represents alveolar rather than bronchial pathology.

Silhouette Sign: Loss of the normal interface between structures of similar density, used to localize pulmonary pathology based on which borders are obscured.

Kerley B Lines: Short horizontal lines at the lung bases representing thickened interlobular septa, characteristic of interstitial pulmonary edema in heart failure.

HRCT: High-resolution computed tomography using thin-slice technique optimized for detailed evaluation of pulmonary parenchyma and interstitial lung disease patterns.

UIP Pattern: Usual interstitial pneumonia characterized by honeycombing, traction bronchiectasis, and basal-peripheral predominance, diagnostic of idiopathic pulmonary fibrosis when clinical criteria are met.

Lung-RADS: Standardized reporting system for lung cancer screening CT that categorizes findings and provides evidence-based management recommendations.

Filling Defect: Intraluminal abnormality within contrast-opacified vessels on CT pulmonary angiography, diagnostic of pulmonary embolism when occurring within pulmonary arteries.

Honeycombing: Clustered thick-walled cystic spaces on high-resolution CT representing established pulmonary fibrosis, most specific finding of usual interstitial pneumonia pattern.

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