Abstract
BackgroundAlthough shear wave elastography (SWE) is reported to be useful in detecting malignant thyroid nodules, it shows a wide range of cut-off values of elasticity index (EI) in detecting malignant nodules. The cause of discrepancy remains unclear. Fibrosis of the tumors is known to increase the EI in SWE, and matching of SWE and surgical histopathology has not been fully illustrated in thyroid cancer. We aimed to evaluate the reproducibility of the new total nodular region of interest (ROI) method excluding the subjective features of focal circular ROI placement and to determine the lesion that causes the elevation of EI on SWE and on histopathology.MethodsA total of 29 thyroid cancers from 28 patients were included. We evaluated the reproducibility of EI in the new total nodular ROI using Q-Box Trace program and compared the EI in focal nodular ROI using a 3-mm circular area. We analyzed the correlation between fibrosis and EI.ResultThe coefficient of variation (CV) of the intrarater assay was significantly lower in total nodular ROI than in focal nodular ROI within the image in rater 1 (1.7% vs. 13.4%, p < 0.001) and in rater 2 (1.4% vs. 16.9%, p < 0.001) and in different images in rater 1 (7.6% vs. 12.3%, p = 0.040) and in rater 2 (7.5% vs. 19.8%, p = 0.004). Moreover, CV of the interrater assay showed similar results (14.9% vs. 19%, p = 0.030). Interrater intraclass correlation coefficient showed better agreement in total nodular ROI than in focal nodular ROI (0.863 vs. 0.783). The degree of fibrosis on histopathology showed significant correlations with EI (EMean, p < 0.001; EMax, p = 0.027), and the location of fibrosis was concordant with the high EI area on SWE.ConclusionOur study revealed that the new total nodular ROI method showed higher reproducibility and better agreement in intra- and interrater assay than the focal nodular ROI method, suggesting a valuable and standardized method in clinical practice. Moreover, our results showed that fibrosis in the histopathology increased EI on SWE and might lead to the discrepancy of the cut-off values in detecting thyroid cancer.
Highlights
Shear wave elastography (SWE) is reported to be useful in detecting malignant thyroid nodules, it shows a wide range of cut-off values of elasticity index (EI) in detecting malignant nodules
The interrater coefficient of variation (CV) of the total nodular region of interest (ROI) method was significantly lower than the focal nodular ROI method (14.9% vs. 19.0%, p = 0.030)
Correlation between elasticity index measurements on shear wave Elastography and the degree of fibrosis on surgical histopathology To evaluate the correlation between EI measurements on shear wave elastography (SWE) and the degree of fibrosis on surgical histopathology, we reviewed and compared the SWE images and the Method of ROI
Summary
Shear wave elastography (SWE) is reported to be useful in detecting malignant thyroid nodules, it shows a wide range of cut-off values of elasticity index (EI) in detecting malignant nodules. We aimed to evaluate the reproducibility of the new total nodular region of interest (ROI) method excluding the subjective features of focal circular ROI placement and to determine the lesion that causes the elevation of EI on SWE and on histopathology. SWE has sufficient quantitative information and is operator independent in terms of compression; it is expected to result in more reproducible findings than strain elastography, and two-dimensional SWE (2D-SWE) represents focal tissue stiffness map [14, 15]. SWE is not operator dependent in terms of the added stress (compression) but operator dependent in the placement of ROI To decrease this subjective variance in the placement of ROI in thyroid nodules, we let the total nodular area the ROI by tracing the total nodular margin using the overlapping B-mode US. We compared the reproducibility and reliability of EI between the total nodular ROI and the focal nodular ROI using 3-mm circular area
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