Thyroid nodules: who to puncture?
Thyroid nodules are found in a significant proportion of the adult population, and the vast majority of them are benign. The doctor’s task is not to miss those few that require intervention, and at the same time not to send everyone for a puncture. The selection is carried out according to the TI-RADS system, which takes into account the shape, contours, echogenicity and the presence of microcalcifications.
Elastography adds stiffness to these features. Colloid nodes and adenomas are usually soft or comparable in density to the surrounding parenchyma. Papillary carcinoma, the most common malignant tumor of the thyroid gland, is characterized by high rigidity. The combination of suspicious ultrasound signs with high elastography values is a strong argument in favor of puncture, and a soft nodule with smooth contours is often left under observation.
The method works worse for nodules with large calcifications and cystic formations: the fluid does not conduct the wave, and the result turns out to be unreliable.
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.