Radiation symptomatology is determined by the type of metastases. Nodal metastases, growing exocardially, are quite well detected with the simplest radiation study — multiprojection radiography. They are displayed by a limited swelling of the contour of the heart shadow, which is not characteristic of any heart disease. The malignant nature of the process is indicated by the roughness, roughness of the contours, the rapid increase in the size of the “bulging”. Detailed characterization of such metastases is possible with CT and MRI, which are the most informative. The sensitivity and specificity of echocardiography in this regard is much less. Miliary metastasis is manifested mainly by signs of rapidly increasing hydropericardium and progressive heart failure. with echocardiography, CT and MRI, among other things, it is possible
detection of uneven thickening of the leaves of the heart bag. In the radiation image, the main symptom of metastatic lesions of the intrathoracic lymph nodes is an increase in their size (the norm is up to
10 mm). Usually X-ray examination (radiography and linear
tomography) is quite effective and even has an advantage over some other radiation methods in detecting changes in bronchopulmonary, right tracheobronchial and right lower paratracheal lymph nodes. Their detectability at the same time reaches 80%. Scylogical increase in bronchopulmonary lymph nodes is characterized by expansion and structurelessness of the lung root, right tracheobronchial – loss of differentiation of the shadow of the unpaired vein, right lower paratracheal – expansion and polycyclic contour of the upper mediastinum.
The expansion of other groups of mediastinal lymph nodes is established much less reliably, especially the para-basal. Evidence of paraaortic lymphadenopathy is the expansion of the upper mediastinum to the left, the indistinguishability of the aortic arch contour, the aortic “window” darkening (the space between the aortic arch and the left branch of the pulmonary artery). An increase in subcarinary lymph nodes may lead to an increase in the trachea bifurcation angle. However, the value of this sign is small, as well as in normal, the value of this angle varies in very large limits (from 28 to 94 o ). More significant is the detection at the level of the trachea bifurcation indentation on the anterior wall and displacement of the esophagus back.
In general, according to our clinical materials, x-ray data on the presence of hilar lymphadenopathy coincide with morphological data only in half of the cases.
Echography is most sensitive in diagnosing lesions of the paravasal lymph nodes (90 o ), and least sensitively to the paratracheal lesions (50 o ) and especially the bronchopulmonary lymph nodes (20 o ).
Ultrasound examination of the mediastinum is performed from the suprasternal and parasternal approaches. The adipose tissue gives an echopositively coarse-grained homogeneous image, against the background of which echo-negative large vessels are clearly visible (aorta and its branches, pulmonary artery, superior vena cava). Unchanged lymph nodes are not visualized.
Echography is the only radiation method that can detect metastases in unlarged lymph nodes. The direct evidence of their metastatic lesion is the appearance of hypoechoic rounded formations 5– mm in size on the echopositive background of cellulose. Indirect signs are the disappearance of the effect of dorsal amplification behind the vessels, their displacement and deformation. When nodes are enlarged to 20 mm, the layer of echopositive fatty tissue between them and the vessels disappears. An even greater volume of damage leads to the disappearance of the image of the vessel wall and the appearance in its lumen of an additional hypoechoic structure, which already indicates the growth of the vessel.
Computed tomography allows you to judge the metastatic lesion of the lymph nodes, unfortunately, only on the basis of their increase. But such an assessment, and with a high degree of accuracy, is available intrathoracic lymph nodes in all regions. True, in detecting an increase in bronchopulmonary, right tracheobronchial and right lower paratracheal lymph nodes, CT does not significantly exceed linear tomography, but it significantly exceeds the capacity of the latter in detecting lymphadenopathy in all other areas. In general, the sensitivity of CT in this regard
exceeds 95%. Lymph nodes on CT get an independent image thanks to
that their densitometric density (+30 … +40 HU) is much higher than the density of the surrounding fatty tissue (-115 … +3 HU). Unchanged lymph nodes are round or oval in shape, the size does not exceed 10 mm. The size of the nodes more than 10 mm suggests a possibility of metastatic lesions. If the dimensions are increased to 15 mm, then histologically tumor cells are found in 70%, and if more than 15 mm, then almost always. However, as it is now established, and non-enlarged lymph nodes in 5—% may contain micrometastases.
Additional signs of lung cancer metastasis to the lymph nodes are their association into conglomerates and loss of differentiation of mediastinal elements. The correspondence of the region of the altered lymph nodes to a specific localization of lung cancer and the sequence of involvement of various groups of lymph nodes in the pathological process is also of diagnostic importance.
In practical terms, it is important that before the lymph nodes, regional for the lung, in which the tumor develops, are completely affected, the process of metastasis within the mediastinum occurs on its side. Only with extensive metastasis, accompanied by a complete blockage of lymphatic collectors from the affected lung and complete disorientation of lymph outflow from this area, metastasis also occurs in the lymph nodes of the opposite side of the mediastinum.
With all the diagnostic significance of CT in the identification of hilar lymphadenopathy, however, it should be borne in mind that this method does not always allow differentiation of metastatic lymph nodes from simple hyperplasia. In such cases, to clarify the nature of changes in mediastinal lymph nodes, it is required to use bioptic methods.
Magnetic resonance imaging in detecting metastases in the intrathoracic lymph nodes has the same limitations as CT. the first is the diagnostic criterion of lymph node damage is only an increase in their size, the second is the inability to differentiate the nature of the lesion. The informativeness of MRI in the diagnosis of the mediastinal lymphadenopathy itself is high and approximately equal to CT.
The intrathoracic lymph nodes are subject to the most thorough assessment even with the minimum size of the primary tumor lesion of the lungs, which by no means excludes the likelihood of lymphogenous metastasis of any degree.
Traditional X-ray examination in the diagnosis of mediastinal lymphadenopathy at the present time should be recognized as clearly insufficient. For these purposes it is necessary to use new ray methods.
Ultrasound examination of the mediastinum in almost half of the patients with lung cancer reveals a greater volume of lesions in the lymph nodes than is imaged by X-ray and linear tomography. But far from all groups of lymph nodes are echographically clearly visualized. Therefore, this volume of damage is often underestimated. CT scan, in addition to ultrasound, reveals new lymphadenopathy regions in another 20%. It is not necessary to use an MRI because it is equally informative with CT. In general, according to the “N” factor, the data of the complex radiation research coincide with the surgical data in 85–% of cases. To conduct a radionuclide study to determine metastasis to the intrathoracic lymph nodes is impractical because it does not have the proper spatial resolution,does not allow to accurately judge the anatomic-topographic localization of the lesion and has low specificity.