Pathology of the chest on computed tomography

Changes in lymph nodes

Normal axillary lymph nodes are usually oval and up to 1 cm in size. Often in their center or at the edge (horseshoe-shaped), a region of reduced density is known, which is known as the "gate sign". Through the hypodense fat gates, the lymph nodes enter the vessels. Many altered lymph nodes lose their normal contour and become round or irregular in shape. In this case, they are defined as a solid structure without a sign of the fat gates.

Increased metastatic lymph nodes usually do not have a clear border and merge with the surrounding fat tissue. They often have in the center a zone of necrosis and they are difficult to distinguish from an abscess with disintegration. If the lymph node damaged by metastases has been removed, or radiotherapy has been performed, the date and nature of the treatment should necessarily be noted in the direction of subsequent CT examinations. The process of healing and scarring after surgery changes the structure of the lymph node, and they become similar to the pathologically altered ones. Therefore, the lack of clinical information significantly complicates the radiologist's diagnostic process.

Breast

The normal structure of the parenchyma of the female breast is characterized by a very uneven contour and thin fingerlike protrusions into the surrounding fatty tissue. Often one can see its bizarre outlines. When breast cancer determines solid formation of irregular shape. The new growth sprouts fascial leaves and infiltrates the chest wall on the side of the lesion. CT scan, conducted immediately after mastectomy. Should help in the clear identification of tumor recurrence. Diagnosis of recurrent neoplasm greatly complicates the presence of fibrotic changes after radiotherapy, post-operative scars and the absence of surrounding fatty tissue. Therefore, special attention should be paid to the regional lymph nodes and bones, so as not to miss metastases to the spine. For this it is necessary to use a bone window.

Bone skeleton of thorax

Osteolytic foci often occur in the bones of the chest. They usually arise from metastatic damage or myeloma.

Tumors

In the anterior mediastinum after therapy with glucocorticoids, benign enlargement of adipose tissue sometimes develops. If there is no confidence in the nature of the lesion, it is necessary to measure the density (densitometry) of the formation. Differential diagnosis of such neoplasms should be carried out with a congestive goiter and thymoma. In the example presented, the average density within the area of interest shows the presence of adipose tissue - 89.3 HU. With a standard deviation of 20 HU. The dimensions of the window of the area of interest can be chosen independently (in cm ² ).

In children and young people, the density of the thymus gland is about + 45 HU. As a result of age involution, its density decreases and after 20 years 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 share should not exceed 1.3 cm, while 1.8 cm is considered the norm at the age of up to 20 years.

Thickening of the walls of the esophagus due to malignant lesion must be differentiated from gastric protrusion after surgery on the esophagus. At subsequent CT studies, it is necessary to exclude the possible increase in lymphatic knots next to the stomach. The remaining metal clips serve as the cause of artifacts that complicate the assessment of the mediastinum. After resection of the esophagus in the anterior mediastinum, the site of the large intestine can be determined. Analysis of adjacent sections shows that this is not an emphysema bulla, but a lumen of an organ with a tubular structure.

Enlarged lymph nodes

Unchanged lymph nodes are often visualized at the level of the aortopulmonary window. Basically, they have an oval or irregular shape, up to 10 mm in diameter and are well delimited from the mediastinal fiber. The presence of lymph nodes in this area usually does not cause suspicion until their dimensions exceed 1.5 cm in diameter. Detection of the "sign of fat gates" is not mandatory for normal lymph nodes, but always confirms their benign nature.

If more than 3 lymph nodes are identified 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.

The increase in lymph nodes of the mediastinum, especially in the region of the roots of the lungs, is characteristic of sarcoidosis (Beck's disease). Pathologically altered lymph nodes of the mediastinum are mainly located also in front of the aortic arch, under tracheal bifurcation and para-aortic (retrocrally).

Pathological changes in blood vessels

Partial mixing of KB with blood should 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 thrombosis. They are the cause of lengthening and widening of the aorta, and as a result may lead to the development of an aneurysm. When the lumen of the vessel is more than 4 cm, the expansion of the thoracic aorta is considered an aneurysmal one. The recording of measured data on tomograms simplifies the estimation of the sizes of these structures during subsequent CT studies. It is important to determine the involvement of large arteries in the process and the signs of stratification (dissection of the walls). Depending on the size of the exfoliated flap, three types of stratification are distinguished (according to de Bakey).

True aneurysms in diameter more than 6 cm, their lumen is usually saccular, spindle-shaped or irregularly shaped. Are prone to tearing, which causes hematoma of the mediastinum, hemothorax or cardiac tamponade.

Strainer aortic aneurysms (de Baieke)

• I type (about 50%) The lamination extends from the ascending aorta to the remaining sections up to the bifurcation.
• II type (about 15%) Lamination is defined only in the ascending aorta to the brachiocephalic trunk.
• III type (about 25%) The intima is damaged and exfoliates distally to the left subclavian artery.

Pulmonary embolism

If a large embolus detached from a thrombus in a deep vein of the lower limb and entered the pulmonary artery, after contrast enhancement it will be visualized as a zone of reduced density in the corresponding artery. In this case, the affected segments or lobes usually begin to poorly ventilate, and atelectasis occurs. The depletion of the pulmonary vascular pattern is noticeable even on the traditional chest X-ray. With CT angiography, the embolus is visualized in the pulmonary artery.

A heart

CT scan is clearly defined as the expansion of the cavities as a result of the failure of valves or cardiomyopathy, as well as cavity filling defects. After the administration of KB, thrombi in the atrium or in the ventricular aneurysm become visible.

The 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 scans, it looks like a ring that widens the outer contour of the heart with a 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 squeezes the surrounding lung tissue, but also limits the function of the heart.

Pericardial effusion can lead to the development of fibrosis or calcification of the pericardium with the occurrence of constrictive pericarditis. Note that in this case, the hollow vein, the unpaired vein and even the atria are significantly enlarged, which is a sign of heart failure.

Atherosclerotic lesion of the coronary arteries is usually accompanied by calcification in the form of fine lines of increased density in the epicardial tissue. However, to complete the assessment of the degree of stenosis, an angiographic examination is necessary.

Lungs

Focal educations of the lungs

Multiple pulmonary metastases can be seen even on the topogram. They look like rounded formations of different sizes, depending on the prescription of their appearance and vascularization. The more uneven contour in pathological formation (for example, stellate or acicular), the more likely it is that it is malignant. However, if this is a single formation with the presence of calcification in its center (kind of popcorn) or on the periphery, it is most likely that it is a benign hamartoma or granuloma.

Metastases in the lungs are not visible on the traditional radiograph, until their diameter reaches 5 - 6 mm. On CT images, they are visible even at a value of 1 - 2 mm. With the localization of metastases in the peripheral parts of the lungs, they are easy to distinguish from the transverse sections of the vessels, and the closer to the roots - the more difficult. In situations requiring more detailed analysis, the VRTC technique should be followed.

It is very important to select the correct window for viewing images. Small focal educations in the lungs in the soft tissue window are not visible or may be mistaken for unchanged vessels. To assess the lung tissue should always use a pulmonary window.

The prevalence of lung cancer, especially among women and young people, is increasing. The most important prognostic factors are histological form, stage and localization. Peripheral lung cancer of considerable size is almost always seen on the traditional chest X-ray. Inoperable lung cancer usually occurs when

Progression of neoplasm of central localization. Tumor growth leads to bronchial obstruction obstruction with the development of collapse in the distal part of the lung.

Lymphogenous lung carcinomatosis extends from the roots or visceral pleura to the interstitial lung tissue along the lymphatic vessels. Filling these vessels with cancer cells leads to a violation of the progress of lymph. Initially, the upper lobe retains its transparency, 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 from both sides. In the case of progression of the process, they spread within the perivascular tissue and along the lymphatic vessels to the periphery of the lungs. During scrap, small multiple focal formations and fibrous changes of interstitial tissue of various degrees are visualized.

Tuberculosis

If a large formation with a cavity is defined at the cut, it is necessary to differentiate lung cancer with central decay and the tubular form of tuberculosis.

Aspergillosis

Aspergillus infection can occur within a previously existing cavity in patients with immunodeficiency. Spores A. Fumigatus are usually found in plants and soil. Often the cavity is filled with aspergillas not completely, with a small edge strip of air remaining. Aspergillosis can also lead to the development of bronchial asthma or provoke the development of exogenous allergic alveolitis.

Pleura

A significant amount of effusion in the pleural cavity can lead to compression of the pulmonary tissue causing atelectasis of individual segments or even a whole lobe of the lung. Pleural effusion is visualized as a homogeneous fluid in the pleural cavity with a density close to water. Usually effusion accompanies infectious processes, stagnant changes in the lungs due to a deficiency of the right heart, as well as venous congestion, mesothelioma and peripheral lung cancer.

If a significant part of the lung was sleeping. It is necessary to insert a tube into the pleural cavity for pleural drainage.

Foreign bodies in the pleural cavities are rare, although sometimes they can remain there after thoracotomy.

Asbestosis and other pneumoconiosis

Asbestosis and other pneumoconiosis are characterized by a reticular deformation of the pulmonary pattern with numerous fine-grained nodules of increased density that are scattered throughout all pulmonary fields with predominant localization in the interlobar gaps. Also typical is the presence of thickenings and overlays on the pleura. In the late stages of the disease, marked fibro-
cirrhotic changes are identified with the presence of emphysema. In this case, spindle-shaped or triangular darkening zones appear that make it difficult to diagnose lung cancer, which is often encountered in this pathology.

Silicosis

In interstitial tissue due to phagocytosis of silicon particles, clearly delineated 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 are better and earlier can be detected using VRTT, where the thickness of the cut is 2 mm instead of the standard 10 mm. Diffuse locations of fine-grained nodules are visible throughout all the summer fields. In the zones of dense fibrosis, manifested by the area of darkening of lung tissue, a cavity is determined. The enlarged lymph nodes of the mediastinum and the roots of the lungs are often visualized with calcification in the form of a shell. With the progression of the disease, fibro-cirrhotic changes and emphysema develop.

Emphysema

In the initial stage in the soft tissue window, inflammatory infiltration of the lung tissue against a background of progressive emphysema with bullae or bronchiectasis is not visible. It is better and faster to identify it on thin sections in the pulmonary window.

The causes of interstitial pulmonary fibrosis can not always be established and then it is considered idiopathic pulmonary fibrosis. Similar changes are especially characteristic for middle-aged women. The symptoms of fibrosis in different diseases look the same, as you could see on the previous pages. Development of emphysematous changes on the scurf background begins with subpleural zones of the lungs. Fibrosis of the lung develops with the progression of the process in patients with systemic connective tissue diseases. For example, similar changes are characteristic for scleroderma or nodular periarteritis.

[1], [2], [3], [4], [5], [6], [7]