What are the key anatomical structures and potential diagnoses that can be identified on a computed tomography (CT) scan of the chest in a typical adult patient with no known medical history?

CT Chest Anatomy: Key Structures and Diagnostic Capabilities

Primary Anatomical Structures Visualized on CT Chest

CT chest imaging provides comprehensive visualization of thoracic anatomy including cardiac structures, great vessels, pulmonary vasculature, mediastinal compartments, airways, lung parenchyma, pleura, chest wall, and lymphatic structures. 1

Cardiovascular Structures

• Cardiac chambers and pericardium are routinely visualized, with modern multidetector CT allowing assessment of cardiac morphology and function even without dedicated cardiac gating 2
• Great vessels including the aorta, pulmonary arteries, superior and inferior vena cava, and subclavian vessels are clearly delineated, particularly with IV contrast 3, 4
• Coronary arteries can be evaluated on high-resolution CT, especially with submillimeter slice thickness and multiplanar reformation 3

Mediastinal Anatomy

• Mediastinal lines and stripes formed by interfaces between pleura, lung, and mediastinal structures provide critical diagnostic information 5
• Lymph nodes throughout the mediastinum are identifiable, with normal and pathologic patterns distinguishable 1
• Thoracic duct and cisterna chyli can be visualized in 55-100% of cases depending on technique, appearing as low-attenuation tubular structures 3

Pulmonary Structures

• Airways from trachea to subsegmental bronchi are evaluated for patency, wall thickening, and anatomic variants 1
• Lung parenchyma with near-isotropic submillimeter resolution allows detection of subtle interstitial and alveolar abnormalities 6, 7
• Pulmonary vasculature including segmental and subsegmental vessels are assessed for emboli, stenosis, or anatomic variants 1

Chest Wall and Pleura

• Osseous structures including ribs, sternum, clavicles, scapulae, and thoracic spine are completely visualized 3
• Pleural spaces and pleural reflections are assessed for effusions, thickening, or pneumothorax 3
• Soft tissues of the chest wall including muscles, subcutaneous tissues, and breast tissue 1

Technical Considerations for Optimal Anatomic Visualization

Contrast Enhancement Protocols

• IV contrast administration significantly improves visualization of vascular structures and mediastinal anatomy, with peak enhancement occurring 15-120 seconds post-injection 8
• Arterial phase imaging (15-30 seconds) optimally demonstrates arterial anatomy and active hemorrhage 8
• Venous phase imaging (120-180 seconds) enhances venous structures and increases detection of mediastinal pathology 4, 8

Acquisition Parameters

• Thin-slice acquisition with 1mm collimation and multiplanar reformation enables identification of small structures like the thoracic duct in nearly 100% of normal anatomy 3
• Submillimeter resolution with near-isotropic voxels allows high-quality 3D reconstructions in any plane 6, 2

Common Diagnostic Patterns and Pathology

Cardiovascular Findings

• Pericardial effusion appears as low-attenuation fluid surrounding the heart; high-attenuation effusion suggests hemopericardium 3
• Cardiac tamponade is suggested by the triad of high-attenuation pericardial effusion, peri-portal low attenuation, and distention of IVC, renal veins, SVC, and azygos veins 3, 4
• Aortic pathology including dissection, aneurysm, and intramural hematoma are detected with near 100% sensitivity and 98% specificity on contrast-enhanced CT 8

Pulmonary Parenchymal Patterns

• Metaphoric CT signs help narrow differential diagnosis, including tree-in-bud pattern, crazy paving, halo sign, and others specific to various lung diseases 7
• Interstitial patterns are best characterized on high-resolution technique, distinguishing reticular, nodular, and ground-glass opacities 7

Mediastinal Abnormalities

• Lymphadenopathy is identified by size criteria (typically >1cm short axis) and enhancement characteristics 1
• Mediastinal masses are localized to anterior, middle, or posterior compartments based on anatomic relationships 5

Pleural and Chest Wall Pathology

• Pleural effusions are characterized by attenuation values: simple transudates measure 0-20 HU, exudates 20-40 HU, hemothorax >40 HU 3
• Osseous abnormalities including cervical ribs, first rib anomalies, and fractures are readily identified 3, 9

Critical Anatomic Spaces

Thoracic Outlet

• Three distinct compression spaces include the interscalene triangle, costoclavicular space, and pectoralis minor space, relevant for thoracic outlet syndrome evaluation 3, 9
• Neurovascular bundles passing through these spaces can be assessed for compression, particularly with dynamic positioning 9

Lymphatic System

• Central lymphatic structures including thoracic duct (visualized in 55% of cases on noncontrast CT) and cisterna chyli (1.7% on noncontrast) are identified by low attenuation and tubular morphology 3

Systematic Interpretation Approach

A systematic review should evaluate each anatomic compartment sequentially: mediastinum (including vascular structures and lymph nodes), lung parenchyma (upper to lower zones), pleura, chest wall, and visible upper abdomen 1. This prevents overlooking subtle findings and ensures comprehensive assessment of all visualized structures.