Manjiri K. Dighe MD, Presenter: Research Grant, General Electric Company

Jeff Thiel, Abstract Co-Author: Nothing to Disclose

Daniel S. Hippe MS, Abstract Co-Author: Research Grant, Koninklijke Philips NV Research Grant, General Electric Company

To compare stiffness measurement within a thyroid nodule using Shear wave elastography (SWE) on transverse (T) and longitudinal (L) images.

After IRB approval, elastograms were obtained by (SWE) from 77 individuals, with a total of 96 thyroid nodules. SWE data was acquired without any external compression using the Supersonics Aixplorer machine. Elastograms were acquired in the transverse (T) and longitudinal (L) orientation. 1 reader blinded to pathology results drew regions of interest (ROIs) covering the entire nodule within each image. The mean stiffness value (SV) was recorded from each ROI and averaged across each nodule for each orientation separately. Nodule SVs were compared between orientations using the Wilcoxon signed-rank test for bias and the concordance correlation coefficient (CCC) for agreement. In those with final histopathology results available, receiver operating characteristic (ROC) curve analysis and the area under the ROC curve (AUC) were used to evaluate how well SVs from each orientation could discriminate malignant and benign lesions.

Mean nodule SVs were 19.3 ± 15.5 kPa on T images and 22.1 ± 20.8 kPa on L images. There was a statistically significant but small bias in measurements between orientations of 2.8 kPa (p=0.003). The SD of differences was 13 kPa and CCC=0.74. After removing two large values, these dropped to 9.9 kPa and CCC=0.52. In the subset of 41 nodules with histopathology available, the AUC for discriminating malignant and benign lesions was 0.76 (p=0.002) using T images and 0.70 (p=0.01) using L images (p=0.28 for the difference).

There was moderate agreement in mean stiffness values measured using transverse and longitudinal orientation but only a small bias. Measurements from both orientations had similar performance in discriminating malignant and benign lesions. Using either orientation for characterizing thyroid nodules is feasible.

Similar diagnostic performance using Shearwave elastography was achievable using transverse and longitudinal orientations, which provides flexibility in imaging patients with short necks or difficulty in laying on the examination bed with an extended neck.

Dighe, M, Thiel, J, Hippe, D, Impact of Image Orientation on Measurements of Thyroid Nodule Stiffness Using Shear Wave Elastography.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012400.html