Original ContributionReal-Time Elastography in the Evaluation of Diffuse Thyroid Disease: A Study Based on Elastography Histogram Parameters
Introduction
Ultrasonography (US) is a tolerable and easily applicable diagnostic method that has been used worldwide in the differential diagnosis of thyroid nodules. US mostly represents the morphologic features of the targeted thyroid mass, and studies have reported high levels of performance with combinations of gray-scale US features in the diagnosis of thyroid nodules (Kim et al., 2002, Moon et al., 2008, Papini et al., 2002). In addition to gray-scale US, there has recently emerged elastography, which provides an estimate of tissue stiffness by measuring the degree of displacement secondary to external compression applied (Asteria et al., 2008, Itoh et al., 2006, Rago et al., 2007). Based on the concept that malignant masses are relatively stiff compared with the adjacent normal parenchyma (Itoh et al., 2006, Yoon et al., 2011), elastography has been used mostly in the differentiation between benign and malignant nodules within the thyroid (Asteria et al., 2008, Dighe et al., 2008, Ding et al., 2012, Hong et al., 2009, Moon et al., 2012, Rago et al., 2007). In addition to evaluation of masses, elastography has been reported to have a role in evaluating the extent of inflammatory infiltrations and fibrosis within the diseased parenchyma (Friedrich-Rust et al., 2007, Sandrin et al., 2003, Wang et al., 2012).
Real-time elastography (RTE) visualizes the elasticity of the target area by capturing echo signals derived secondary to repetitive compressions applied with a freehand technique (Kanamoto et al., 2009, Wang et al., 2012, Yoon et al., 2011). A quantitative analysis method based on RTE has been developed that can be used on diffuse pathologic lesions, such as liver fibrosis, as reported in several studies (Friedrich-Rust et al., 2007, Kanamoto et al., 2009, Wang et al., 2012). Results of these studies have proved that the quantitative data obtained from RTE constitute a useful, non-invasive imaging method with promising results in the assessment of liver fibrosis in patients with chronic hepatitis. Similarly, thyroid stiffness assessment has been used in the diagnosis of diffuse thyroid gland pathology with acoustic radiation force impulse elastography (Sporea et al. 2011b) or shear wave elastography (Kim et al. 2014) in several recent studies, with promising results. Quantitative parameters obtained from RTE may also be helpful in the diagnosis and management of patients with diffuse thyroid disease (DTD). The 11 elastography parameters used in RTE, which are calculated by maneuvering the ultrasound unit, each display characteristics related to the elastography image, factors related to the elastography histogram and factors related to the gray-scale co-occurrence matrix. Also, the “elastic index,” calculated on the basis of the 11 parameters derived from RTE by principal component analysis used in the diagnosis of liver fibrosis (Wang et al. 2012), may be applied to the thyroid gland. Although RTE parameters, including elastic index, have been used to evaluate fibrosis in liver parenchyma, to our knowledge, there are no other studies reporting the application of quantitative RTE parameters and the elastic index to the diagnosis of DTD. On this basis, we evaluated the diagnostic performance of quantitative histogram parameters using high-technology RTE in the diagnosis of patients with DTD.
Section snippets
Methods
Informed written consent was obtained from all patients. The study was performed in accordance with the ethics guidelines of the Helsinki Declaration and was approved by the institutional review board of Severance Hospital, Seoul, Korea.
Results
According to the pathology results, 31 patients were positive for DTD, and the remaining 85 patients were negative for DTD. Mean ages of the patients with (46.8 ± 11.0 y) and patients without (42.3 ± 10.3 y) DTD did not significantly differ (p = 0.054). The ratio of men to women among patients with DTD (2/29) did not significantly differ from that among patients without DTD (19/66) (p = 0.681). The mean interval between pre-operative staging US and thyroid surgery was 0.9 mo (range, 0.1–2.3 mo).
Discussion
Gray-scale US features that are known to be useful in the evaluation of DTD are decreased or increased parenchymal echogenicity, coarse-appearing echotexture, changes in vascularity, decreased or increased anteroposterior diameter of each gland, marginal nodularity and the presence of scattered microcalcifications (Kim et al. 2010). Although the aforementioned US features may suggest the presence of DTD, clinical or laboratory features are more accurate and generally used in the evaluation and
Conclusions
We evaluated the usefulness of RTE, including the elastic index, in the differential diagnosis of thyroid nodules. The results indicated that the MEAN and elastic index performed well and comparably. On the basis of our results, we conclude that RTE using the elastic index performs well diagnostically and may be useful in the diagnosis and management of patients with diffuse thyroid disease.
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2019, Ultrasound in Medicine and BiologyCitation Excerpt :There were five continuous and stable troughs, one of which was selected for observation of the elastogram. Eleven quantitative parameters were obtained, including the mean value of the relative strain within the ROI (MEAN); the standard deviation of the relative strain ratio within the ROI (SD); the area of the low-strain region (%AREA); the complexity of each low-strain area (boundary length2/area) (COMP); kurtosis (KURT), which evaluates if the histogram distribution can be concentrated into an average value; a scale of asymmetry that indicates the degree in which the histogram is skewed (SKEW); the feature value of the textual variations (the greater the resolution, the greater the contrast) (CONT); the feature value of the textual randomness, entropy (ENT); the feature value of the textual homogeneity, the inverse difference moment (IDM); the feature value of textual uniformity, the angular second moment (ASM); the directivity of the texture, reflecting the degree of similarity of the texture in the row and column directions, correlation (CORR) (Shi et al. 2014; Yoon et al. 2014). The average of five repeated measurements was taken as the final result.
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2017, Ultrasound in Medicine and BiologyCitation Excerpt :They had a classification accuracy of 93.6% in differentiating between benign and malignant nodules. Histogram analysis of the color elastograms (elasticity index and mean) were used for diagnosis and management of patients with diffuse thyroid disease (Cantisani et al. 2015a, 2015b; Yoon et al. 2014), and another study indicated excellent inter-observer agreement (Lim et al. 2012). Recommendation 5.
Histogram and gray level co-occurrence matrix on gray-scale ultrasound images for diagnosing lymphocytic thyroiditis
2016, Computers in Biology and MedicineCitation Excerpt :To overcome these limitations, there have been many quantitative studies that have focused on diagnosing DTD with USE (US elastography) as well as gray-scale US [1,8,9,11,20–22] (Table 5) and both methods have shown good diagnostic performances. The Az value of the mean was 0.737 in a study using USE [9] and 0.8 [21] in a study using conventional US combined with USE utilizing shear waves. The study which investigated and compared the diagnostic performance of conventional US and USE using shear waves to diagnose DTD revealed that USE using shear waves had a higher Az value (0.619) than conventional gray-scale US (Az=0.585) [8].
Variability in Interpretation of Ultrasound Elastography and Gray-Scale Ultrasound in Assessing Thyroid Nodules
2016, Ultrasound in Medicine and BiologyCitation Excerpt :Gray-scale ultrasound (US) is the most sensitive test currently available for detecting thyroid lesions; however, differentiation of benign and malignant nodules is not highly accurate with gray-scale ultrasound (Takashima et al. 1995), and thus, its diagnostic value varies considerably from study to study (Fish et al. 2008; Frates et al. 2006; Kim et al. 2002; Kovacevic and Skurla 2007; Lim et al. 2012). Ultrasound elastography (USE) enables the assessment of tissue consistency by differentiating stiff nodules from soft nodules, and it supplements the diagnostic limitations of gray-scale US (Asteria et al. 2008; Azizi et al. 2013; Bamber et al. 2013; Cantisani et al. 2014; Hong et al. 2009; Kagoya et al. 2010; Kim et al. 2014; Mehrotra et al. 2013; Moon et al. 2012; Rago et al. 2007; Rubaltelli et al. 2009; Shuzhen 2012; Shweel and Mansour 2013; Trimboli et al. 2012; Unluturk et al. 2012; Yoon et al. 2014). Previous studies suggested that with respect to diagnostic performance, USE is better or comparable to gray-scale US when differentiating benign from malignant thyroid nodules (Asteria et al. 2008; Azizi et al. 2013; Cantisani et al. 2014; Hong et al. 2009; Rago et al. 2007; Shuzhen 2012; Trimboli et al. 2012).