Screening of thyroid nodules by ultrasound elastography using diastolic strain variation

The diagnosis for thyroid nodules is currently made via an FNA biopsy. It is estimated that somewhere between 250,000 and 300,000 thyroid FNA biopsies are performed in the United States annually. However, a large percentage (approximately 70%) of these biopsies turn out to be benign. The purpose of this study is to evaluate whether ultrasound elastography can be used as a screening tool to reduce the number of FNA procedures on benign thyroid nodules. Ultrasound data previously acquired from 34 thyroid nodules in 31 FNA-bound patients were used. Pulsation from the carotid artery was used to compress the thyroid nodules, and the strain was calculated off-line. A metric, called diastolic strain variation index (DSVI), was computed for each nodule during diastole as the standard deviation of strain within a thyroid nodule. Based on the derived DSVI value, thyroid nodules were retrospectively classified into 2 types: I) no FNA (observation-only) and II) FNA. The DSVI value of benign nodules (n = 22) was significantly higher than that of malignant nodules (n = 12) (p = 0.0000016). Using an DSVI cut-off value of 0.019%, 18 nodules were classified as type I, all of which were benign, while 16 nodules were classified as type II, 12 malignant and 4 benign. This suggests that ultrasound elastography could have screened out 18 type-I nodules, reducing the number of FNAs by 53%. Because aggressive FNA management of thyroid nodules is costly, thyroid elastography could be employed in the future for more appropriate utilization of healthcare resources in handling thyroid nodules.