Endocrine Abstracts

Background: Elastography is an ultrasound technique that allows to predict risk of malignancy of examined lesion by assessing their stiffness. Its effectiveness in thyroid nodules is equivocal which may result from insufficient standardization.

Aim: Analysis of factors affecting the repeatability and reproducibility of elastographic measurements of thyroid nodules.

Methods: 124 nodules in 118 patients were analyzed. Elastographic measurements were made qualitatively by using the 4-grade elastic score (ES) and quantitatively by evaluating the strain ratio (SR) between the nodule and the surrounding tissue. Reproducibility was tested by three investigators. Influence of the following factors on SR and ES was examined: imaging section (transversal/longitudinal), location of the nodule (isthmus/other), presence of other lesions superficially to the examined nodule, thickness of the fatty tissue (≤5 mm/>5 mm), size of the nodule, its distance from the skin surface (≤10 mm/>10 mm), percent of the cystic part in nodule (≤25%/25–50%). Furthermore, influence of ultrasonographic malignancy risk factors (MRF) was analyzed. Intraclass correlation coefficient (ICC) was used as a measure of consistency for SR and coefficient κ Cohen’s – for ES.

Results: Good mean repeatability and moderate mean reproducibility of ES assessment (κ=0.47 and 0.38, respectively; P<0.0001 both) as well as very good mean repeatability and good mean reproducibility SR assessment (ICC=0.73, P<0.0001 and ICC=0.53, P<0.0005) were observed. Blurred nodule’s margins decreased reproducibility of SR (ICC=0.510 vs 0.478, P<0.0001) and ES (κ=0.39 vs 0.35, P<0.0005). Other factors, especially other MRFs did not affect reproducibility and repeatability of elastography in the examined model (nodules <25 ml, located not deeper than 25 mm, the fat tissue thickness <15 mm, percentage of cystic part <50%).

Conclusion: Elastography in relation to the thyroid nodules has satisfactory repeatability and reproducibility of measurements. The presence of MRF, apart from blurred margin of the nodule, does not significantly affect elasticity measurements.