Reactive node or metastasis
An enlarged lymph node is a common finding, and in most cases it is a reaction to a past infection. But the same sign is the first manifestation of a metastatic lesion or lymphoma, so the question about the nature of the node constantly arises. Conventional ultrasound evaluates the shape, size ratio, integrity of the node gates and the nature of the blood flow, but in borderline cases these data are not enough.
The reactively enlarged lymph node retains its normal architecture and remains soft. With metastatic lesions, tumor cells replace the tissue of the node, it becomes dense and looks uniformly stiff on the elastogram. In lymphomas, the stiffness is usually intermediate, which also carries diagnostic information.
The study is most often used for monitoring after treatment of breast cancer, thyroid cancer and head and neck tumors - where regional nodes need to be monitored regularly. As in other areas, the result serves as a basis for puncture, and does not replace it.
What does elastography show?
Elastography measures the stiffness (elasticity) of tissue - a parameter that a doctor could previously assess only with his hands during palpation. Healthy tissue is soft and easily deformed, while scar, fibrous and tumor tissue is dense and rigid. The method translates this feeling into objective numbers that can be compared between studies.
The main practical value is in the differential diagnosis of focal formations. Benign nodes usually retain the elasticity of the surrounding tissue, while malignant ones are noticeably stiffer. This helps decide which nodes need to be monitored and which ones require a biopsy.
Compression and shear wave techniques
Compression elastography is based on light pressure with a sensor: the device compares tissue deformation and builds a color map. The method is qualitative - it shows what is harder and what is softer, but does not give absolute values.
Shear wave elastography (shear wave, which also includes liver fibroscan) uses the acoustic pulse of the device itself and measures the speed of propagation of the shear wave. The result is quantitative - in kilopascals, which allows you to track the dynamics during treatment.
Limitations of the method
The result is influenced by severe obesity, edema and active inflammation in the area of interest, as well as the depth of the formation: the deeper it is, the less reliable the measurements. Large calcifications and cysts produce artifacts.
Elastography is not an independent diagnosis, but one of the parameters. The final conclusion about the nature of the formation is given by a morphological study, that is, a biopsy.