Computed tomography of the chest
Last reviewed: 23.04.2024
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As a rule, computed tomography of the thoracic cavity is carried out in the transverse direction (axial sections) with a cut thickness and scanning step of 8-10 mm. For example, when making slices with a thickness of 10 mm, with an overlap of 1 mm, table advance is carried out in 8 mm steps. Better to navigate in the localization of anatomical structures on the slices will help you the scheme that accompanies the corresponding CT images. In order not to miss pathological changes in the lungs, it is necessary to print slices in the soft tissue as well as in the pulmonary window on the printer or to store the video information of the research on CD. In this case, each slice can be viewed in either of the two windows. On the other hand, a large number of images inevitably entail the need for a clear system of their evaluation, so as not to waste time looking through the sections haphazardly.
Sequence analysis of CT images
Beginners often ignore the examination of the soft tissues of the chest wall because they automatically consider the examination of the lungs and mediastinal organs more important. But, first of all, it is necessary to evaluate the tissues of the chest wall. Pathological changes are usually localized in the mammary gland and axillary fatty tissue. Then, using the installed soft tissue window, go to the search for pathological formations of the mediastinum. The aortic arch, which even an inexperienced researcher will find, will help you navigate in the structures located here. Above the arch of the aorta, the upper mediastinum is located, where the pathological formations should be distinguished from the large vessels situated nearby: the brachiocephalic trunk, the left common carotid artery, and the subclavian artery. Also nearby are the brachiocephalic vein, the upper hollow vein and the trachea, and somewhat posteriorly the esophagus. Typical sites of localization of enlarged LUs below the aortic arch: aortopulmonary window, right under the bifurcation of the trachea, in the region of the roots of the lungs and next to the descending aorta behind the diaphragm legs (retro-turns). Normally, in the aortopulmonary window, it is possible to detect several lymph nodes up to 1.5 cm in diameter. Lymph nodes of normal size lying anterior to the aortic arch are rarely seen on CT. The study in the soft tissue window is considered complete when the heart (coronarosclerosis, the expansion of the cavities) and the roots of the lungs are studied (vessels are clearly distinguishable and there is no expansion or deformation). Only after all this the radiologist passes to the pulmonary or pleural window.
Due to the considerable width of the pleural window, in addition to the lung tissue, bone marrow in the vertebral bodies is well visualized. Along with the pulmonary vessels, bone structure can also be evaluated. When examining the vessels of the lungs, attention should be paid to their width, which normally decreases gradually from the roots to the periphery. The depletion of the vascular pattern is normally determined only along the boundaries of the lobes and on the periphery.
In order to distinguish volumetric formations from the cross sections of vessels, it is necessary to compare neighboring sections. More or less rounded volumetric educations can be metastases in the lungs.
Printing images in the superimposed window (pulmonary and soft tissue) is not justified, because pathological formations of the density level between these windows will not be visible.
Recommendations for reading chest computer tomography
Soft-woven window:
- soft fabrics, pay special attention to:
- axillary lymph nodes,
- mammary glands (malignant neoplasms?)
- four departments of the mediastinum:
- above the arch of the aorta (lymph nodes, thymoma / goiter?)
- the roots of the lungs (the size and configuration of the vessels, expansion and deformation?)
- heart and coronary arteries (sclerosis?)
- four typical locations of lymph nodes:
- in front of the aortic arch (normal to 6 mm or not defined)
- aortopulmonary window (normally up to 4 LU, up to 15 mm in diameter)
- Bifurcation (normal to 10 mm, not to be confused with the esophagus)
- para-aortic (normal to 10 mm, not to be confused with an unpaired vein)
Pulmonary window
- Pulmonary tissue:
- Branching and the size of the vessels (normal, dilated, deformed?)
- depletion of the vascular pattern (only along the interlobar cracks in the bullae?)
- focal formation, inflammatory infiltration?
- Pleura:
- pleural overlaps, adhesions, calcifications, hydrothorax, hemothorax, pneumothorax?
- Bones (spine, ribs, scapula, sternum)
- structure of the bone marrow?
- signs of degenerative lesion (osteophytes)?
- foci of osteolysis or osteosclerosis?
- narrowing of the spinal canal?
If during the scan in the subclavian vein there is a significant concentration of KB, artifacts appear at the level of the upper aperture of the chest. The thyroid parenchyma should have a uniform structure and be clearly delineated from the surrounding fiber. The asymmetry of the diameter of the jugular veins occurs quite often and is not a pathology. From axillary lymph nodes it is necessary to distinguish cross sections of branches of axillary and external thoracic vessels. If the patient's hands are raised above the head during the examination, the supraspinatus will be located next to the inner part of the shoulder blade and the subacute muscle. Large and small pectoral muscles are usually separated by a thin layer of fat.
Normal anatomy
CT sections of the chest also go and are displayed from the bottom. Therefore, the left lung is visualized on the right side of the image and vice versa. It is necessary to know well the trunk vessels originating from the arch of the aorta. From the front to the subclavian artery, the left common carotid artery and the brachiocephalic trunk adjoin. More to the right and to the front are seen the brachiocephalic veins, which after merging on the slices form the upper hollow vein. In the axillary tissue, it is often possible to recognize normal lymph nodes by their characteristic form with a fat-density gate. Depending on the angle of the section, lymph nodes on the cut, the gate of reduced density is visualized in the center or along the edge. The normal lymph nodes of the axillary region are clearly delineated from the surrounding tissues and do not exceed 1 cm in diameter.
Computed tomography of the thorax is normal
Principles of high resolution CT (BPKT)
For the construction of the image VRTT use thin sections and an algorithm for reconstructing sections with high spatial resolution. Traditional CT scanners are also capable of performing thinner slices than standard 5-8 mm. If necessary, change the parameters of the image formation by setting the working console to a thickness of cuts of 1-2 mm.
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.
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