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Methods of ultrasound of the lymph nodes of the neck
Last reviewed: 23.04.2024
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Assessment of lymph nodes is performed after their visualization, which is performed by rotating the sensor and displaying the lymph node along the longitudinal axis. The maximum longitudinal dimension is divided in two by a perpendicular transverse dimension. The ratio M / P (the ratio of the maximum longitudinal and transverse dimensions) characterizes the shape of the lymph node. If it is less than 2, the node has a spherical shape, which makes it possible to suspect its metastatic damage. This criterion is not applicable to nodes smaller than 1 cm, because the measurement error is too large. Metastases in lymph nodes measuring less than 1 cm or larger than 4 cm are often nonspherical. Lymph nodes larger than 4 cm are suspicious by the length of the maximum size. Therefore, the ratio of M / P is mainly used for lymph nodes with a maximum size of 1-2 cm, because in these limits there is an overlap between benign and malignant lymph nodes.
In the study of normal lymph nodes and lymph nodes affected by nonspecific lymphadenitis, a hypoechoic cortex with a bright central echo in the gates is determined. In metastatic lesions and in malignant lymphomas, in 50-80% of cases there is no echo in the gates. With malignant lymphoma, the pronounced hypoechogenicity of the cortex is often determined, which can create pseudocysts. Metastases to the lymph nodes often have a complex echostructure due to regressive changes. Lymphonoduses normally normally are strictly limited, but in the presence of metastases, the boundaries become fuzzy.
For color duplex evaluation of the lymph nodes, examine the intra-arterial vessels in color Doppler mode. Assess the degree and pattern of vascularization, then place the trial volume in the largest vessels and record the Doppler frequency spectrum. Carrying out the angular correction is not necessary, since only the parameters of the IP and the IS are of interest. With metastasis of scaly fibrotic cancer in lymph nodes, the resistance index is higher than in benign nodes. With ICs greater than 0.8 and PIs greater than 1.6, metastases are diagnosed with a sensitivity of about 55% and a specificity of 95%. A larger index of metastatic resistance in the lymph nodes is the result of the obstruction of the peripheral vascular channels by tumor cells. Both malignant lymphoma and lymphadenitis are characterized by a low resistance index (IC <0.8).
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