Radiological imaging methods of the trachea
Multislice computed tomography (MSCT) is used for a detailed assessment of the tracheobronchial tree. The scan is performed at full inspiration. Comprehensive analysis of the obtained data requires various modes and reconstructions:
- Axial CT (lung and mediastinal windows): allows the study of the cross-section of the airways, detection of intraluminal soft-tissue nodules, evaluation of the shape of the narrowed segment, and monitoring of treatment dynamics (e.g., reduction in wall thickness after a course of antibiotics).
- Coronal oblique multiplanar reconstruction (MPR): the slice is aligned along the longitudinal axis of the trachea. Averaged images (e.g., with a slice thickness of 21 mm) clearly visualize the cartilaginous rings. This is the optimal option for assessing the vertical extent of stenosis.
- 3D reconstruction (virtual endoscopy) and volumetric rendering (volumetric rendering): clearly demonstrate the internal relief of the lumen throughout its length. They make it possible to distinguish a smooth surface from an irregular (irregular) or nodular (nodular) one, as well as clearly visualize fistulous tracts (fistula).
Stenoses and inflammatory diseases
Post-intubation stenosis Develops as a complication after intubation, frequently in patients with severe background conditions (e.g., severe chronic obstructive pulmonary disease — COPD).
- CT signs: circular luminal narrowing (circumferential luminal narrowing) is observed due to soft tissue thickening (typically over a length of about 2 cm). On coronal slices, a specific "hourglass" sign (hourglass configuration) is revealed. On axial tomograms, the narrowed lumen often acquires a triangular shape, while during 3D modeling, the inner surface appears slightly irregular and nodular.
Infectious tracheobronchitis A severe bacterial infection caused by Pseudomonas aeruginosa, Escherichia coli, or Streptococcus. Typical for patients with severe immunodeficiency (e.g., in agranulocytosis secondary to cyclophosphamide therapy for vasculitis and rheumatoid arthritis). Manifests with cough and shortness of breath (dyspnoea).
- CT presentation: marked stenosis of the distal trachea and proximal main bronchi (often asymmetric, with left-sided predominance). Irregular wall thickening is visualized. Areas of lucency (lucency) corresponding to fistulous tracts (fistulous tract) communicating with paratracheal submucosal abscesses may be identified within the wall.
Tumors of the large airways
Malignant neoplasms Primary tracheal carcinomas more often demonstrate eccentric growth, causing asymmetric narrowing (circumferential involvement is rare). Tumors can be polypoid in shape and located predominantly intraluminally (intraluminal). In 30–40% of cases, mediastinal extension (mediastinal extension) is observed. Differential diagnosis based on surface characteristics:
- Squamous cell carcinoma (squamous cell carcinoma): the tumor surface is often irregular.
- Adenoid cystic carcinoma (adenoid cystic carcinoma): the surface is usually smooth.
The main treatment method is surgical resection with anastomosis followed by radiation therapy.
Secondary (metastatic) lesions Occur via hematogenous metastasis or direct invasion (direct invasion) from the thyroid gland, esophagus, lungs, and mediastinal structures. Melanoma (melanoma) and renal cell carcinoma (renal cell carcinoma) have the highest propensity for hematogenous metastasis to the trachea.
- CT presentation: changes are focal (focal) in nature. Intraluminal soft-tissue nodules, local wall thickening, and distal bronchoceles are visualized.
Benign neoplasms Less common. The most frequent types include hamartomas (hamartoma), lipomas, leiomyomas, and neurogenic tumors. Their imaging features include well-demarcated contours (well-demarcated), a regular rounded shape, and small dimensions.
Briefly: answers to topical questions
What symptoms and complications are characteristic of secondary tracheal lesions?
The provided materials do not describe the clinical symptoms of secondary tracheal lesions. For secondary malignancies of the large airways, the following features are indicated:
- Pathways of involvement: hematogenous metastasis and direct invasion (direct invasion) from the esophagus, thyroid gland, mediastinum, or lung.
- Tumors prone to metastasize to the trachea and main bronchi: renal cell carcinoma (renal cell carcinoma) and melanoma (melanoma).
- CT presentation: changes are usually focal (focal), including intraluminal soft-tissue nodules (intraluminal soft-tissue nodules) and wall thickening.
- Additional finding: distal bronchoceles (distal bronchoceles) may be visualized.
What are the standard scanning and patient preparation protocols for tracheal MSCT?
For the evaluation of tracheal pathologies, the provided materials specify the following CT/MSCT protocol elements:
- MSCT is performed at full inspiration; it is followed by multiplanar reformations (multiplanar reformations).
- Multiplanar reconstruction helps evaluate the location, extent, and degree of luminal narrowing, the location and extent of wall thickening, as well as the nature of the internal surface of the tracheal lumen.
- Standard position for chest CT: supine (supine), scanning from the lung apices to the lung bases at full inspiration.
- Paired inspiratory and expiratory scans can be useful for the non-invasive confirmation of tracheobronchomalacia or excessive dynamic airway collapse.
- For HRCT, intravenous contrast administration should be avoided unless there are other clinical indications.
For differential diagnosis of primary tracheal cancer by surface character, you can use the association: Squamous cell — Surface Scrappy (irregular), Adenoid cystic — Absolutely smooth.
Class and exam questions
Which type of reconstruction best demonstrates the extent of tracheal stenosis?
Coronal oblique multiplanar reconstruction (MPR) along the longitudinal axis of the trachea, as well as virtual 3D endoscopy, are optimal.
How does post-intubation stenosis appear on CT in different projections?
On coronal slices, it forms a characteristic "hourglass" configuration, while on axial slices, the lumen often acquires a triangular shape.
Which tumors most frequently metastasize to the trachea via hematogenous routes?
Hematogenous metastases to the large airways are most characteristic of melanoma and renal cell carcinoma.
What else to study on this topic
- Preoperative evaluation of the extent of malignant tracheal tumors
- The role of volumetric rendering in surgical treatment planning
- Differential diagnosis of the causes of circular and asymmetric tracheal narrowing
- Radiological dynamics of infectious tracheobronchitis during antibiotic therapy
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