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Chest pathology on a CT scan
Last reviewed: 04.07.2025

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Changes in lymph nodes
Normal axillary lymph nodes are usually oval in shape and up to 1 cm in size. Often, they have a low-density area in the center or at the edge (horseshoe-shaped appearance), which is known as the "portal sign". Vessels enter the lymph nodes through the hypodense fatty porta. Many altered lymph nodes lose their normal contour and acquire a round or irregular shape. In this case, they are determined as a solid structure without the fatty porta sign.
Enlarged metastatic lymph nodes usually have no clear border and merge with the surrounding fatty tissue. They often have a necrotic zone in the center and are difficult to distinguish from an abscess with decay. If the lymph node affected by metastases has been removed or radiation therapy has been performed, the date and nature of the treatment should be noted in the referral for subsequent CT examinations. The healing and scarring process after surgery changes the structure of the lymph node, and they become similar to pathologically changed ones. Therefore, the lack of clinical information significantly complicates the diagnostic process for the radiologist.
Breast
The normal structure of the female mammary gland parenchyma is characterized by a very uneven contour and thin finger-like protrusions into the surrounding fatty tissue. Its bizarre outlines can often be seen. In breast cancer, a solid formation of irregular shape is determined. The neoplasm grows through the fascial sheets and infiltrates the chest wall on the affected side. CT scanning performed immediately after mastectomy should help in clearly identifying tumor recurrence. The diagnosis of tumor recurrence is significantly complicated by the presence of fibrous changes after radiation therapy, postoperative scars and the absence of surrounding fatty tissue. Therefore, special attention should be paid to regional lymph nodes and bones in order not to miss metastases to the spine. For this, it is necessary to use a bone window.
Bone skeleton of the thorax
Osteolysis foci are often found in the bones of the chest. They usually arise as a result of metastatic lesions or myeloma.
Tumors
In the anterior mediastinum, after glucocorticoid therapy, benign enlargement of adipose tissue sometimes develops. If the nature of the lesion is uncertain, it is necessary to measure the density (densitometry) of the formation. Differential diagnostics of such neoplasms should be carried out with retrosternal goiter and thymoma. In the presented example, the average density value within the area of interest shows the presence of adipose tissue - 89.3 HU. with a standard deviation of 20 HU. The size of the window of the area of interest can be selected independently (in cm 2 ).
In children and young people, the density of the thymus gland is about + 45 HU. As a result of age-related involution, its density decreases and after 20 years it becomes equal to the density of adipose tissue (- 90 HU). Often, the left lobe of the thymus gland is larger than the right and can reach the aortopulmonary window. In adults, the size of the lobe should not exceed 1.3 cm, while 1.8 cm is considered normal at the age of up to 20 years.
Esophageal wall thickening due to malignancy must be differentiated from gastric protrusion after esophageal surgery. Subsequent CT scans must exclude possible enlargement of the lymph nodes near the stomach. Metal clips remaining after surgery cause artifacts that complicate the assessment of the mediastinum. After esophageal resection, a section of the colon may be seen in the anterior mediastinum. Analysis of adjacent sections shows that this is not an emphysematous bulla, but a lumen of an organ with a tubular structure.
Enlarged lymph nodes
Normal lymph nodes are often visualized at the level of the aortopulmonary window. They are usually oval or irregular in shape, up to 10 mm in diameter, and well demarcated from the mediastinal tissue. The presence of lymph nodes in this area usually does not arouse suspicion until their size exceeds 1.5 cm in diameter. Detection of the "fatty hilum sign" is not mandatory for normal lymph nodes, but always confirms their benign nature.
If more than 3 lymph nodes are detected in the aortopulmonary window, or if a single lymph node is pathologically enlarged, the differential diagnosis includes not only lung cancer metastases, but also lymphoma.
Enlargement of the mediastinal lymph nodes, especially in the area of the lung roots, is characteristic of sarcoidosis (Beck's disease). Pathologically altered mediastinal lymph nodes are also predominantly located in front of the aortic arch, under the bifurcation of the trachea and paraaortic (retrocrural).
Pathological changes in blood vessels
Partial mixing of KB with blood must be distinguished from possible thrombi in the lumen of the brachiocephalic vein. Sometimes thrombi can be fixed to the central venous catheter.
Atherosclerotic plaques in the aorta are often accompanied by thrombus formation. They cause the aorta to lengthen and widen, and can eventually lead to the development of an aneurysm. If the lumen of the vessel is more than 4 cm, the widening of the thoracic aorta is considered aneurysmal. Recording the measured data on tomograms simplifies the assessment of the size of these structures during subsequent CT examinations. It is important to determine the involvement of large arteries in the process and signs of dissection (wall dissection). Depending on the size of the detached flap, three types of dissection are distinguished (according to de Bakey).
True aneurysms are larger than 6 cm in diameter, and their lumen is usually saccular, fusiform, or irregular in shape. They tend to rupture, causing mediastinal hematoma, hemothorax, or cardiac tamponade.
Dissecting aortic aneurysms (according to de Bakey)- Type I (about 50%) Dissection extends from the ascending aorta to the remaining sections up to the bifurcation.
- Type II (about 15%) Dissection is determined only in the ascending aorta up to the brachiocephalic trunk.
- Type III (about 25%) The intima is damaged and detached distally to the left subclavian artery.
Pulmonary embolism
If a large embolus breaks away from a thrombus in a deep vein of the lower limb and enters the pulmonary artery, after contrast enhancement it will be visualized as a low-density zone in the corresponding artery. In this case, the affected segments or lobes usually begin to be poorly ventilated, and atelectasis occurs. The depletion of the pulmonary vascular pattern is noticeable even on a traditional chest X-ray. With CT angiography, an embolus is visualized in the pulmonary artery.
Heart
CT examination clearly identifies both the expansion of the cavities due to valve insufficiency or cardiomyopathy and the filling defects of the cavities. After the introduction of CB, thrombi in the atrium or in the ventricular aneurysm become visible.
Fluid in the pericardial cavity appears in viral infections, chronic renal failure, systemic connective tissue diseases, extensive infarction, tuberculosis and many other diseases. On CT sections, it looks like a ring expanding the outer contour of the heart with low fluid density (between 10 and 40 HU). Fresh blood has a higher density. A large amount of fluid in the pericardial cavity not only compresses the surrounding lung tissue, but also limits the function of the heart.
Pericardial effusion may lead to fibrosis or calcification of the pericardium, resulting in constrictive pericarditis. Note that in this case, the vena cava, azygos vein, and even the atria are significantly dilated, which is a sign of heart failure.
Atherosclerotic lesions of the coronary arteries are usually accompanied by their calcification in the form of thin lines of increased density in the epicardial tissue. However, angiographic examination is necessary for a complete assessment of the degree of stenosis.
Lungs
Focal lung lesions
Multiple pulmonary metastases can be seen even on a topogram. They look like round formations of varying sizes, depending on how long ago they appeared and how vascularized they are. The more uneven the contour of the pathological formation (for example, star-shaped or needle-shaped), the more likely it is malignant. However, if it is a single formation with calcification in its center (popcorn appearance) or on the periphery, it is most likely a benign hamartoma or granuloma.
Lung metastases are not visible on a traditional radiograph until their diameter reaches 5-6 mm. On CT images, they are visible even at a size of 1-2 mm. When metastases are localized in the peripheral parts of the lungs, they are easily distinguished from the cross-sections of the vessels, and the closer to the roots, the more difficult it is. In situations requiring a more detailed analysis, the VRCT method should be used.
It is very important to choose the right window for viewing images. Small focal lesions in the lungs are not visible in the soft tissue window or may be mistaken for normal vessels. The lung window should always be used to evaluate lung tissue.
The incidence of lung cancer, especially among women and young people, is increasing. The most important prognostic factors are histologic type, stage, and location. Peripheral lung cancer of significant size is almost always visible on a conventional chest X-ray. Inoperable lung cancer usually occurs when
Progression of a neoplasm of central localization. Tumor growth leads to obstruction of the bronchial lumen with the development of collapse in the distal part of the lung.
Lymphogenic lung carcinomatosis spreads from the roots or visceral pleura into the interstitial tissue of the lung along the lymphatic vessels. Filling these vessels with cancer cells leads to disruption of lymph flow. Initially, the upper lobe remains transparent, but as the disease progresses, its infiltration appears. Gradually, large lymphatic vessels and lymph nodes are affected by metastases.
Sarcoidosis
Changes in the lungs in sarcoidosis must be differentiated from multiple lung metastases. Epithelial granulomas in sarcoidosis usually affect the lymph nodes in the roots on both sides. In case of progression of the process, they spread within the perivascular tissue and along the lymphatic vessels to the periphery of the lungs. In LOM, small multiple focal formations and fibrous changes in the interstitial tissue of varying severity are visualized.
Tuberculosis
If a large formation with a cavity is determined on the section, it is necessary to differentiate lung cancer with central decay and the cavitary form of tuberculosis.
Aspergillosis
Aspergillus infection can occur within a pre-existing cavity in immunocompromised patients. A. fumigatus spores are commonly found in plants and soil. Often the cavity is not completely filled with aspergilli, leaving a small marginal strip of air. Aspergillosis can also cause bronchial asthma or provoke the development of exogenous allergic alveolitis.
Pleura
A significant volume of effusion in the pleural cavity can lead to compression of the lung tissue and cause atelectasis of individual segments or even an entire lobe of the lung. Pleural effusion is visualized as a homogeneous fluid in the pleural cavity with a density close to water. Effusion usually accompanies infectious processes, congestive changes in the lungs due to right heart failure, as well as venous congestion, mesothelioma and peripheral lung cancer.
If a significant portion of the lung has collapsed, it is necessary to insert a tube into the pleural cavity to perform pleural drainage.
Foreign bodies in the pleural cavities are rare, although they may occasionally remain there after thoracotomy.
Asbestosis and other pneumoconioses
Asbestosis and other pneumoconioses are characterized by reticular deformation of the pulmonary pattern with numerous fine-grained nodules of increased density, which are scattered throughout all pulmonary fields with predominant localization at the interlobar fissures. Also typical is the presence of thickenings and deposits on the pleura. In the late stages of the disease, pronounced fibrous-
cirrhotic changes with the presence of emphysema are determined. In this case, spindle-shaped or triangular darkening zones appear, which complicate the diagnosis of lung cancer, which is often encountered in this pathology.
In the interstitial tissue, due to phagocytosis of silicon particles, clearly defined multiple nodules are visualized, which are mainly localized in the upper lobes of the lungs. As the process progresses, fibrosis develops with the formation of a honeycomb structure of the lung tissue. These signs can be better and earlier identified using VRCT, where the slice thickness is 2 mm instead of the standard 10 mm. Diffusely located fine-grained nodules are visible across all lung fields. In areas of dense fibrosis, manifested by an area of darkening of the lung tissue, a cavity is determined. Enlarged lymph nodes of the mediastinum and roots of the lungs are often visualized with calcification in the form of a shell. With the progression of the disease, fibrous-cirrhotic changes and emphysema develop.
Emphysema
In the initial stage, inflammatory infiltration of the lung tissue against the background of progressive emphysema with bullae or bronchiectasis is not visible in the soft tissue window. It is better and faster to detect it on thin sections in the pulmonary window.
The causes of interstitial pulmonary fibrosis cannot always be determined and then it is considered idiopathic pulmonary fibrosis. Such changes are especially characteristic of middle-aged women. Signs of fibrosis in various diseases look the same, as you could see on the previous pages. The development of emphysematous changes on this background begins with the subpleural zones of the lungs. Pulmonary fibrosis develops with the progression of the process in patients with systemic diseases of connective tissue. For example, such changes are characteristic of scleroderma or nodular periarteritis.