Interobserver Agreement for Thyroid Elastography

Objectives The purpose of our study was to investigate interobserver agreement for thyroid ultrasound elastography and to analyze the reproducibility of real‐time freehand elastography in thyroid nodules. Methods A prospective nonrandomized double‐blind study was conducted between September 2008 and June 2010. Real‐time elastography of 89 thyroid nodules was performed by two radiologists, with the first radiologist evaluating each thyroid nodule 5 minutes before the second. The elastograms were obtained with the patients holding their breath and considered valid when the quality factor was 50 or higher. The region of interest was positioned to include the nodule and 0.5 cm of surrounding normal thyroid parenchyma but to exclude the carotids and esophageal‐tracheal structures. The elastograms were classified on a scale of 5 different patterns. Results Observers 1 and 2 coincided in 79 elastographic patterns and disagreed on 10 nodules (11.2%). The results between the radiologists had a statistically significant agreement (P < .005), with a κ value of 0.838. Conclusions The introduction of a quality factor in elastographic software and the selection of elastograms with a quality factor of 50 or higher confer almost perfect interobserver agreement for thyroid nodule elastography and make elastography a reproducible technique that could be used in daily clinical practice.