Real-time elastography: a useful tool for predicting malignancy in thyroid nodules with nondiagnostic cytologic findings

Impact of ultrasound elastography in evaluating Bethesda category IV thyroid nodules with histopathological correlation

Introduction

Fine needle aspiration (FNA) is the gold standard method recommended in the diagnosis of thyroid nodules. Bethesda IV cytology results are identified in 7-9% of nodules investigated through FNA, with reported malignancy rate in a wide range of 10-40%. The recommended treatment is either surgical or risk additional molecular testing before surgery. However, a large number of nodules belonging to this category (60-80%) are observed to be benign after surgical excision, which can put the patient at risk of unnecessary surgical morbidity. This study aimed to assess the diagnostic performance of conventional ultrasound, the ACR TI-RADS score and elastography in cases of Bethesda IV cytology on FNA.

Methods

We evaluated ninety-seven consecutive cases with Bethesda category IV results on FNA by using conventional B-mode ultrasound, qualitative strain or shear-wave elastography (Hitachi Preirus Machine, Hitachi Inc., Japan and Aixplorer Mach 30 Supersonic Imagine, Aix-en-Provence, France) and all nodules were classified according to the ACR TI-RADS system. Conventional ultrasound was used to categorize the nodules as potentially malignant based on the following features: hypoechogenicity, inhomogeneity, a taller than wide shape, irregular margins, presence of microcalcifications, an interrupted thyroid capsule and suspicious cervical lymph nodes. Elastography classified nodules with increased stiffness as suspicious for malignancy.

Results

We considered pathology results as the gold standard diagnosis, finding that 32 out of 97 nodules were carcinomas (33%) and 65 out of 97 were benign nodules (67%). The benign group included twenty cases of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP). Finally, we compared ultrasound data with pathology results, which showed that nineteen out of the 32 malignant nodules presented with increased stiffness on elastography (p=0.0002). On conventional ultrasound, we found that microcalcifications (p=0.007), hypoechogenicity and irregular margins (p=0.006) are features which can distinguish between benign and malignant nodules with statistical significance.

Discussion

Integrating elastography as a parameter of the ACR TI-RADS score in the evaluation of Bethesda category IV nodules showed a sensitivity of 90.62% in detecting thyroid cancer cases (p=0.006). We can conclude that elastographic stiffness as an addition to high risk features observed on conventional ultrasound improves the detection of malignant nodules in cases with Bethesda IV cytology.

Diagnostic accuracy of B-mode ultrasound, ultrasound elastography and diffusion weighted MRI in differentiation of thyroid nodules (prospective study)

Background

The incidence of the thyroid nodules and its detection is increasing rapidly. The most precise method for diagnosis of the nodules of the thyroid is FNAC. But, about 10–20% of specimens of FNAC are indeterminate and non-diagnostic. Therefore, there is a demand for another diagnostic method for evaluating thyroid nodules. Thyroid ultrasound elastography may improve the ability to differentiate malignant from benign thyroid nodules. Few articles were published about the results of DW MRI in thyroid nodules, with its results confirmed that malignant nodules have lower mean ADC values than benign nodules. This study aims to investigate and compare the accuracy of B-mode ultrasound, ultrasound elastography and diffusion-weighted MRI in characterization of the nodules of the thyroid.

Results

The study included 56 patients with thyroid nodules (36 benign and 20 malignant). Thyroid ultrasound, ultrasound elastography and DWI were done for all patients. Ultrasound-guided FNA Cytological examination (as the gold standard) was done for 48 patients and surgical histopathology was done to 8 patients with non-diagnostic FNAC. The results showed: TIRADS score had sensitivity 90%, specificity 77.8% and accuracy of 82.14%. The elastography score had sensitivity 80%, specificity 88.9% and accuracy 85.7%. The use of the strain ratio had 80% sensitivity, 94.4% specificity and 89.3% accuracy. DWI and ADC value had 100% sensitivity and 94.4% specificity and the accuracy was 96.4% for differentiating malignant from benign thyroid nodules. Multi-parametric analysis by TIRADS and ADC had 100% accuracy.

Conclusion

Ultrasound elastography add valuable data over ultrasound TIRADS. But, diffusion weighted MRI and ADC value has more accuracy in differentiating malignant from benign thyroid nodules. The best performance was achieved by the combination of ACR-TIRADS and ADC value.

2021 Korean Thyroid Imaging Reporting and Data System and Imaging-Based Management of Thyroid Nodules: Korean Society of Thyroid Radiology Consensus Statement and Recommendations

Incidental thyroid nodules are commonly detected on ultrasonography (US). This has contributed to the rapidly rising incidence of low-risk papillary thyroid carcinoma over the last 20 years. The appropriate diagnosis and management of these patients is based on the risk factors related to the patients as well as the thyroid nodules. The Korean Society of Thyroid Radiology (KSThR) published consensus recommendations for US-based management of thyroid nodules in 2011 and revised them in 2016. These guidelines have been used as the standard guidelines in Korea. However, recent advances in the diagnosis and management of thyroid nodules have necessitated the revision of the original recommendations. The task force of the KSThR has revised the Korean Thyroid Imaging Reporting and Data System and recommendations for US lexicon, biopsy criteria, US criteria of extrathyroidal extension, optimal thyroid computed tomography protocol, and US follow-up of thyroid nodules before and after biopsy. The biopsy criteria were revised to reduce unnecessary biopsies for benign nodules while maintaining an appropriate sensitivity for the detection of malignant tumors in small (1-2 cm) thyroid nodules. The goal of these recommendations is to provide the optimal scientific evidence and expert opinion consensus regarding US-based diagnosis and management of thyroid nodules.

Ultrasound of benign thyroid nodules: A 120 months follow-up study

OBJECTIVE

Some evidence suggests that most benign nodules exhibit no significant size increase during 5 years of follow-up, although conflicting results have emerged. The aim of the present study is to evaluate the frequency and the magnitude of growth in benign nodules during 120 months of follow-up.

DESIGN

We reviewed the medical and imaging records of patients who were submitted to ultrasound-guided FNA of thyroid nodules at our hospital from January 2007 to March 2009. We selected only patients with benign nodules who underwent annual ultrasound evaluation in our Department.

RESULTS

Among 966 selected patients, 289 were lost during follow-up, meaning that the total number of patients analysed was 677 (474 women and 203 men), with a mean age of 45.6 (16-71) years. In 559/677 patients (82.7%), the size of the nodule remained stable during follow-up; 42 (6.2%) patients experienced spontaneous nodule shrinkage, and 75 (11.1%) patients showed nodule growth. Patients with or without nodule growth during follow-up were superimposable at baseline for age, gender, TSH values, number of patients on levothyroxine treatment and nodule characteristics. All baseline variables in predicting nodular growth were entered to an adjusted multivariate logistic regression model. None of the parameters taken into account was associated with nodular growth.

CONCLUSIONS

In conclusion, the majority of benign nodules remained stable over the period of monitoring. On the basis of our experience, we recommend ultrasound examination at a distance of 2 and 5 years following cytological evaluation, then every 4-5 years from then on.

Diagnostic reliability of elastography in thyroid nodules reported as indeterminate at prior fine-needle aspiration cytology (FNAC): a systematic review and Bayesian meta-analysis

OBJECTIVES

To assess the diagnostic yields of elastography in thyroid nodules reported as indeterminate in FNAC according to guidelines.

METHODS

Databases of Medline, Embase, and Cochrane Central were searched till 31 October 2019. Two different reviewers check the studies and extracted the data. The diagnostic accuracy and yield were quantitatively synthesized using Bayesian bivariate model in R.

RESULTS

Twenty studies with 1734 indeterminate thyroid nodules undergoing elastography were included. The summary estimates of sensitivity and specificity were 0.766 (95% credible interval (CrI), 0.686-0.835) and 0.867 (95% CrI, 0.780-0.931), respectively. The summary estimate for diagnostic odds ratio (DOR) was 25.9 (95% CrI, 12.8-46.2). Summary receiver operating characteristic plots for elastography showed a right-diagonal curvilinear relationship, suggesting a trade-off between sensitivity and specificity, and the estimate of area under curve (AUC) was 0.743. The summary estimates for positive and negative likelihood ratios were 6.6 (95% CrI, 4.2-11.3) and 0.27 (95% CrI, 0.21-0.36), respectively.

CONCLUSIONS

Elastography had fair diagnostic yields in indeterminate thyroid nodules. Shear wave elastography and strain ratio elastography could be more efficient in diagnosis and should evolve in the next years while combing elastography with ultrasound would contribute more to sensitivity and specificity currently.

KEY POINTS

• Elastography has fair diagnostic yields in indeterminate thyroid nodules. • Shear wave elastography and strain ratio elastography are more efficient than real-time elastography. • Combining elastography and other ultrasound techniques improves evaluation of indeterminate thyroid nodules.

The values of shear wave elastography in avoiding repeat fine-needle aspiration for thyroid nodules with nondiagnostic and undetermined cytology

OBJECTIVE

To evaluate the value of shear wave elastography (SWE) in avoiding repeat fine-needle aspiration of thyroid nodules with nondiagnostic and undetermined cytology.

METHODS

A total of 232 thyroid nodules with nondiagnostic (n = 132) and undetermined (n = 100) cytology underwent ultrasound (US) and SWE, followed by repeat ultrasound (US)-guided fine-needle aspiration cytology (FNAC). The final diagnosis was based on cytological or pathological findings. The US and SWE characteristics of benign and malignant nodules were compared using the χ² -test. The receiver operating characteristic (ROC) curves of the thyroid imaging reporting and data system (TI-RADS) categories from the US and the E_Mean and E_SD from the SWE were graphed, and the areas under the curves (AUCs) were compared using a Z test.

RESULTS

There were significant differences between the benign and malignant nodules in terms of the echogenicity, shape, margin, calcification and TI-RADS categories (all P < 0.05). The differences were significant between the malignant and benign nodules for E_Mean [(34.57 ± 14.81) kPa vs. (19.18 ± 7.09) kPa] and E_SD [(13.68 ± 13.01) kPa vs. (3.97 ± 2.58) kPa] (both P < 0.001). Though the difference in the AUCs of E_Mean (0.864) and E_SD (0.876) was not significant (P = 0.745), they both had higher diagnostic performances in comparison with TI-RADS categories (0.762) (all P < 0.05). Moreover, E_SD attained a sensitivity of 100% with a relatively higher specificity of 49.75% when its cut-off value was 3.3 kPa.

CONCLUSIONS

Shear wave elastography is a promising imaging method for reducing repeat FNAC for benign thyroid nodules with nondiagnostic and undetermined cytology when using E_SD as an index.

The Value of Elasticity Contrast Index in the Differential Diagnosis of Thyroid Solid Nodules

OBJECTIVES

To assess the clinical value of elasticity contrast index (ECI) in differentiating malignant thyroid nodules from benign ones.

METHODS

Conventional ultrasound and elastography with pulsation of the carotid artery used as the compression source were retrospectively reviewed on 175 patients (143 females and 32 males; mean ± SD age, 45.17 ± 11.45 years) with 236 solid nodules (113 malignant and 123 benign). All nodules were confirmed by fine-needle aspiration or surgery to be accurately diagnosed. Elasticity contrast index values were computed and used to quantify local stiffness contrast within a nodule as determined with elastography. Elasticity contrast index values between the malignant and benign groups were compared and then related with pathological results. Diagnostic performance of this method was evaluated with use of the receiver operating characteristic curve.

RESULTS

Mean ± SD ECI values for malignant thyroid nodules were significantly greater than those for benign nodules (3.67 ± 1.20 vs 1.80 ± 0.74, P < 0.01). Area under the receiver operating characteristic curve of ECI values was 0.907 (95% confidence interval, 0.867-0.948), and the best cutoff point was 2.16, leading to a sensitivity of 90.3%, specificity of 82.9%, positive predictive value of 83.7% and negative predictive value of 91.2%.

CONCLUSIONS

Elasticity contrast index values can serve as a useful parameter in the differential diagnosis of solid thyroid nodules. With the use of ECI values, objective quantitative information on the tumor stiffness can be achieved to improve diagnostic confidence.

The Role of Ultrasound and Shear-Wave Elastography in Evaluation of Cervical Lymph Nodes

Aim

To evaluate the prognostic value of ultrasound and shear-wave elastography (SWE) in diagnosing malignant cervical lymph nodes.

Methods

A total of 99 patients with enlarged lymph nodes (99 lymph nodes presenting as a neck mass) were examined clinically with conventional ultrasound including Doppler examination and shear-wave elastography. The results of the examinations were compared with the final diagnosis.

Results

There were 43 benign and 56 malignant lymph nodes in our cohort. Age and sex were significant predictors of malignancy. The standard ultrasound parameters—node size, long/short axis ratio, hilum, vascularization, and the presence of microcalcifications—were also statistically significant. Lymph node volume combined with age showed the best predictive power. The maximum stiffness found on SWE was also a significant predictor of malignancy. The combination of epidemiologic, classic ultrasound, and elastographic parameters yielded the highest sensitivity and specificity in the prediction of malignancy; however, the additional impact of elastographic parameters was low.

Conclusion

A combination of epidemiologic and classic ultrasound parameters can discriminate between malignant and benign lymph nodes with satisfactory sensitivity and specificity. Examining the stiffness of lymph nodes by means of SWE does not add much new predictive power.

Nodular Thyroid Disease in the Era of Precision Medicine

Management of thyroid nodules in the era of precision medicine is continuously changing. Neck ultrasound plays a pivotal role in the diagnosis and several ultrasound stratification systems have been proposed in order to predict malignancy and help clinicians in therapeutic and follow-up decision. Ultrasound elastosonography is another powerful diagnostic technique and can be an added value to stratify the risk of malignancy of thyroid nodules. Moreover, the development of new techniques in the era of "Deep Learning," has led to a creation of machine-learning algorithms based on ultrasound examinations that showed similar accuracy to that obtained by expert radiologists. Despite new technologies in thyroid imaging, diagnostic surgery in 50-70% of patients with indeterminate cytology is still performed. Molecular tests can increase accuracy in diagnosis when performed on "indeterminate" nodules. However, the more updated tools that can be used to this purpose in order to "rule out" (Afirma GSC) or "rule in" (Thyroseq v3) malignancy, have a main limitation: the high costs. In the last years various image-guided procedures have been proposed as alternative and less invasive approaches to surgery for symptomatic thyroid nodules. These minimally invasive techniques (laser and radio-frequency ablation, high intensity focused ultrasound and percutaneous microwave ablation) results in nodule shrinkage and improvement of local symptoms, with a lower risk of complications and minor costs compared to surgery. Finally, ultrasound-guided ablation therapy was introduced with promising results as a feasible treatment for low-risk papillary thyroid microcarcinoma or cervical lymph node metastases.

Ultrasound elastography of the thyroid: principles and current status

Ultrasound (US) elastography has been introduced as a non-invasive technique for evaluating thyroid diseases. This paper presents a detailed description of the technical principles, peculiarities, and limitations of US elastography techniques, including strain elastography and shear-wave elastography. This review was conducted from a clinical perspective, and aimed to assess the usefulness of US elastography for thyroid diseases in specific clinical scenarios. Although its main focus is on thyroid nodules, the applications of US elastography for other thyroid diseases, such as diffuse thyroid diseases and thyroiditis, are also presented. Furthermore, unresolved questions and directions for future research are also discussed.

Clinical efficacy of novel elastography using acoustic radiation force impulse (ARFI) for diagnosis of malignant thyroid nodules

Objective

Acoustic radiation force impulse (ARFI) imaging is a recent ultrasound elastography technique; consequently, its efficacy is not fully known. In this study, we compared ARFI imaging with conventional strain elastography (SE) and shear wave velocities (SWVs) to evaluate the utility of ARFI imaging for diagnosing thyroid nodules.

Subjects and Methods

In this study we examined 233 thyroid nodules (183 benign nodules and 50 malignant nodules) isolated from human patients. The nodules were evaluated with SE and ARFI imaging, and SWVs of the nodules were simultaneously measured. ARFI images were classified using a four‐point score based on grayscale intensity of the images. The sensitivity, specificity, and diagnostic accuracy were compared between SE and ARFI imaging. Finally, SWVs for each score of SE and ARFI imaging were compared.

Results

The new scoring system for ARFI imaging can be divided into four virtual touch imaging (VTI) scores. Nodules with a VTI score of 3 or 4 as determined by ARFI imaging were determined to be malignant. The sensitivity, specificity, and diagnostic accuracy, respectively, were 63.2%, 66.3%, and 65.6% for SE, compared with 80.0%, 86.3%, and 85.0% for ARFI imaging. The median SWVs of the nodules were 1.57 m/s, 1.73 m/s, 1.88 m/s, and 2.09 m/s for VTI scores of 1, 2, 3, and 4, respectively. The SWVs of VTI scores 3 and 4 were significantly higher than those of VTI scores 1 and 2.

Conclusions

The diagnostic accuracy of ARFI imaging for differentiating malignant thyroid nodules was higher than that of SE. The VTI scores of the nodules accurately reflected their SWVs.

Level of Evidence

4

Preliminary study of confounding factors of elastography and the application of fine-needle aspiration in thyroid nodules with indeterminate elastography

To investigate confounding factors of real-time ultrasound elastography (RTE) and to evaluate the diagnostic performance of ultrasound (US)-guided FNA for thyroid nodules with indeterminate elastography compared with conventional US. This study included 244 nodules with indeterminate elastography caused by several confounding factors (large or small size, deep location, isthmic or paratracheal location, calcification, thyroiditis, conflicting results between conventional US and RTE), and corresponding prevalences of malignancy were calculated. Additionally, conventional US and US-FNA data were collected and compared. The prevalences of malignancy of confounding factors were 74.1%, 75.0%, 73.3%, 46.2%, 27.3%, and 53.2%, respectively. Sonographic features (border, margin, echogenicity, echohomogeneity, and microcalcification) were significantly different between benign and malignant thyroid nodules (p < 0.05), and most of them exhibited good sensitivity but unsatisfactory specificity and accuracy. While US-FNA exhibited better performance with a sensitivity of 96.9%, a specificity of 99.1% and an accuracy of 98.0% in the diagnosis of malignancy. Given that indeterminate RTE is inevitable with a rather high malignant risk due to several confounding factors, our study revealed that US-FNA was a valuable tool in nodules with indeterminate elastography by increasing the detection rate of thyroid malignancy.

Head and neck ultrasound: technical advances, novel applications and the role of elastography

High-resolution ultrasound (US) provides superb anatomical detail in the superficial anatomy of the neck and has become the first-line imaging investigation for neck lumps and a crucial component of clinical pathways. In this article, a wide range of advances in neck US are described with a focus on the emerging role of ultrasound elastography. Selected examples of clinical utility are presented across a spectrum of scenarios with discussion of newer applications, service delivery, and training issues. The changing role of the neck ultrasound practitioner and the future of the technique in the head and neck are considered.

Differential Diagnosis of Parotid Gland Tumors: Role of Shear Wave Elastography

AIM

To create a predictive score for the discrimination between benign and malignant parotid tumors using elastographic parameters and to compare its sensitivity and specificity with standard ultrasound.

METHODS

A total of 124 patients with parotid gland lesions for whom surgery was planned were examined using conventional ultrasound, Doppler examination, and shear wave elastography. Results of the examinations were compared with those ones of histology.

RESULTS

There were 96 benign and 28 malignant lesions in our cohort. Blurred tumor margin alone proved to be an excellent predictor of malignancy with the sensitivity of 79% and specificity of 97%. Enlarged cervical lymph nodes, tumor vascularisation, microcalcifications presence, homogeneous echogenicity, and bilateral occurrence also discriminated between benign and malignant tumors. However, their inclusion in a predictive model did not improve its performance. Elastographic parameters (the stiffness maxima and minima ratio being the best) also exhibited significant differences between benign and malignant tumors, but again, their inclusion did not significantly improve the predictive power of the blurred margin classifier.

CONCLUSION

Even though elastography satisfactorily distinguishes benign from malignant lesions on its own, it hardly provides any additional value in evaluation of biological character of parotid gland tumors when used as an adjunct to regular ultrasound examination.

US Elastography Using Carotid Artery Pulsation May Increase the Diagnostic Accuracy for Thyroid Nodules with US-Pathology Discordance

This study evaluated the diagnostic performance of ultrasound elastography (USE) using carotid arterial pulsation and determined the reproducibility of USE for thyroid nodules. A total of 148 patients with 173 thyroid nodules participated. The mean elasticity contrast index (ECI) was significantly higher in malignant nodules (3.1 ± 1.5) than in benign nodules (1.7 ± 0.8) (p < 0.001). When a cut-off ECI value of 3.5 was used, the diagnostic accuracy (78.6%) of gray-scale ultrasound (US) + ECI was the highest compared with that of the gray-scale US (76.9%) and ECI (67.1%). In 16 of 43 nodules (37.2%) with US-pathology, discordance could be correctly reclassified as benign (8 of 11) or malignant (8 of 32). The intra-class correlation coefficient for inter-observer agreement was 0.96, and those for intra-observer agreement were 0.97 and 0.98. Thyroid nodules with ECI values of >3.5 may have an additional value to increase the diagnostic accuracy for nodules with US-pathology discordance with reproducible results.

Evaluation of hypofunctioning thyroid nodules with technetium-99m MIBI and ultrasonography

Background: Fine needle aspiration cytology (FNAC) cannot reliably differentiate follicular adenoma from follicular carcinoma (FC), which requires histological evidence of capsular or vascular invasion. FC is the most predominant thyroid cancer in our loco-regional environment, indicating the need for improvement in preoperative diagnostic accuracy of thyroid nodules to ensure appropriate and timely interventions.Objective: The purpose of this study was to assess the role of technetium-99m methoxyisobutylisonitrile (99mTc-MIBI) scintigraphy and ultrasonography (USG) in the differential diagnosis of thyroid nodules.Methods: Forty-two patients with hypofunctioning thyroid nodules were prospectively studied with 99mTc-MIBI scintigraphy and USG to differentiate benign from malignant nodules. An injection of 740 MBq of 99mTc-MIBI was intravenously administered, followed by semiquantitative analysis of dual-phase scans using a 4-point (0 to 3) scoring system. USG was subsequently performed and interpretation was based on some sonographic criteria for malignancy. In the following days and weeks, patients underwent FNAC followed by surgery and histopathologic examination.Results: All malignant nodules were positive on 99mTc-MIBI and all but two malignant nodules were positive on USG. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy are, respectively, 100%, 70%, 65%, 100%, and 81% for 99mTc-MIBI scintigraphy; 87%, 78%, 68%, 91% and 81% for USG; and 83%, 100%, 100%, 96% and 64% for FNAC. There was no statistically significant difference between 99mTc-MIBI scintigraphy and USG performance for both benign (p = 0.317) and malignant (p = 0.573) nodules.Conclusion: 99mTc-MIBI scintigraphy and USG are important imaging modalities in the evaluation of thyroid nodules, particularly follicular neoplasms which are frequently associated with non-diagnostic cytology.

WFUMB Guidelines and Recommendations on the Clinical Use of Ultrasound Elastography: Part 4. Thyroid

The World Federation for Ultrasound in Medicine and Biology (WFUMB) has produced guidelines for the use of elastography techniques including basic science, breast and liver. Here we present elastography in thyroid diseases. For each available technique, procedure, reproducibility, results and limitations are analyzed and recommendations are given. Finally, recommendations are given based on the level of evidence of the published literature and on the WFUMB expert group's consensus. The document has a clinical perspective and is aimed at assessing the usefulness of elastography in the management of thyroid diseases.

Shear-Wave Elastography for Papillary Thyroid Carcinoma can Improve Prediction of Cervical Lymph Node Metastasis

BACKGROUND

This study aimed to investigate whether the elasticity index of shear-wave elastography (SWE) can predict cervical lymph node (LN) metastasis of papillary thyroid carcinoma (PTC).

METHODS

This retrospective study included 363 patients with a surgical diagnosis of PTC who underwent preoperative SWE evaluation. The elasticity indices of PTC (E _mean, E _max, E _min, E _ratio-p, and E _ratio-m) and gray-scale ultrasound (US) parameters (extrathyroidal extension, multifocality, and cervical LN metastasis) were correlated with the pathologic staging parameters. The optimal cutoff values for the elasticity indices were determined for the prediction of cervical LN metastasis, and diagnostic performance was compared between gray-scale US and the combined application of gray-scale US and SWE.

RESULTS

The findings showed E _mean and E _max to be associated with central LN metastasis (P = 0.037) and E _min to be associated with lateral LN metastasis (P = 0.015). An E _mean value higher than 124 kPa or an E _max value higher than 138 kPa with suspicious gray-scale US findings improved the sensitivity and area under the curve (AUC) for predicting central LN metastasis (sensitivity, 45.4 and 44.6 % vs. 28 %, P < 0.001; AUC, 0.659 and 0.667 vs. 0.615, P = 0.011 and 0.019), whereas an E _min value higher than 63 kPa with suspicious gray-scale US findings improved the sensitivity and AUC for predicting lateral LN metastasis (sensitivity, 95.8 vs. 75 %, P = 0.025; AUC, 0.924 vs. 0.871, P = 0.047).

CONCLUSION

The quantitative elasticity index of PTC on preoperative SWE could be useful for predicting cervical LN metastasis.

Virtual Touch Tissue Imaging for Differential Diagnosis of Thyroid Nodules: Additional Value of the Area Ratio

OBJECTIVES

To evaluate the additional value of the area ratio on Virtual Touch tissue imaging (VTI; Siemens Medical Solutions, Mountain View, CA) for diagnosis of thyroid nodules referred to surgery.

METHODS

From April 2013 to February 2014, 205 consecutive patients with 225 histologically proven thyroid nodules were enrolled in this retrospective study. Virtual Touch tissue imaging and area ratio measurements were performed for each nodule. The area ratio was defined as the area of the nodule on VTI divided by the area on B-mode sonography. Nodule stiffness on VTI was graded from I (soft) to VI (hard). Receiver operating characteristic curve analyses of VTI, area ratio, and the combination of VTI and area ratio were performed. The sensitivity, specificity, accuracy, positive predictive value (PPV), negative predictive value (NPV), and Youden index were also evaluated.

RESULTS

By receiver operating characteristic curve analyses, the cutoff values were VTI grade IV and area ratio of 1.09, respectively. Nodules with VTI grade IV or higher or area ratio of 1.09 or higher were more likely to be malignant. The sensitivity, specificity, accuracy, PPV, NPV, and Youden index were 78.6%, 92.3%, 88.0%, 82.1%, 90.5%, and 0.709 for VTI and 81.4%, 87.1%, 85.3%, 74.0%, 91.2%, and 0.685 for area ratio (all P > .05). However, when using the criterion of VTI grade IV or higher and area ratio of 1.09 or higher as a combination, the sensitivity, specificity, accuracy, PPV, NPV, and Youden index increased to 94.3%, 97.4%, 96.4%, 94.3%, 97.4%, and 0.917 (all P< .05 compared to VTI or area ratio alone, except for specificity between VTI and the combination).

CONCLUSIONS

The diagnostic performance of VTI grading and the area ratio for differentiation between benign and malignant thyroid nodules is equivalent. The performance is further improved with a combination of VTI grading and area ratio analysis.

Ultrasonography Diagnosis and Imaging-Based Management of Thyroid Nodules: Revised Korean Society of Thyroid Radiology Consensus Statement and Recommendations

The rate of detection of thyroid nodules and carcinomas has increased with the widespread use of ultrasonography (US), which is the mainstay for the detection and risk stratification of thyroid nodules as well as for providing guidance for their biopsy and nonsurgical treatment. The Korean Society of Thyroid Radiology (KSThR) published their first recommendations for the US-based diagnosis and management of thyroid nodules in 2011. These recommendations have been used as the standard guidelines for the past several years in Korea. Lately, the application of US has been further emphasized for the personalized management of patients with thyroid nodules. The Task Force on Thyroid Nodules of the KSThR has revised the recommendations for the ultrasound diagnosis and imaging-based management of thyroid nodules. The review and recommendations in this report have been based on a comprehensive analysis of the current literature and the consensus of experts.

Quantitative Evaluation for Differentiating Malignant and Benign Thyroid Nodules Using Histogram Analysis of Grayscale Sonograms

OBJECTIVES

To evaluate the diagnostic value of histogram analysis using grayscale sonograms for differentiation of malignant and benign thyroid nodules.

METHODS

From July 2013 through October 2013, 579 nodules in 563 patients who had undergone ultrasound-guided fine-needle aspiration were included. For the grayscale histogram analysis, pixel echogenicity values in regions of interest were measured as 0 to 255 (0, black; 255, white) with in-house software. Five parameters (mean, skewness, kurtosis, standard deviation, and entropy) were obtained for each thyroid nodule. With principal component analysis, an index was derived. Diagnostic performance rates for the 5 histogram parameters and the principal component analysis index were calculated.

RESULTS

A total of 563 patients were included in the study (mean age ± SD, 50.3 ± 12.3 years;range, 15-79 years). Of the 579 nodules, 431 were benign, and 148 were malignant. Among the 5 parameters and the principal component analysis index, the standard deviation (75.546 ± 14.153 versus 62.761 ± 16.01; P < .001), kurtosis (3.898 ± 2.652 versus 6.251 ± 9.102; P < .001), entropy (0.16 ± 0.135 versus 0.239 ± 0.185; P < .001), and principal component analysis index (-0.386±0.774 versus 0.134 ± 0.889; P < .001) were significantly different between the malignant and benign nodules. With the calculated cutoff values, the areas under the curve were 0.681 (95% confidence interval, 0.643-0.721) for standard deviation, 0.661 (0.620-0.703) for principal component analysis index, 0.651 (0.607-0.691) for kurtosis, 0.638 (0.596-0.681) for entropy, and 0.606 (0.563-0.647) for skewness. The subjective analysis of grayscale sonograms by radiologists alone showed an area under the curve of 0.861 (0.833-0.888).

CONCLUSIONS

Grayscale histogram analysis was feasible for differentiating malignant and benign thyroid nodules but did not show better diagnostic performance than subjective analysis performed by radiologists. Further technical advances will be needed to objectify interpretations of thyroid grayscale sonograms.

Thyroid Imaging Reporting and Data System and Ultrasound Elastography: Diagnostic Accuracy as a Tool in Recommending Repeat Fine-Needle Aspiration for Solid Thyroid Nodules with Non-Diagnostic Fine-Needle Aspiration Cytology

The Thyroid Imaging Reporting and Data System (TIRADS) has been found to be accurate in the stratification of malignancy risk, and elastography has been found to have a high negative predictive value in non-diagnostic thyroid nodules. Through assessment of 104 solid non-diagnostic thyroid nodules, this study investigated the role of both in recommending repeat ultrasonography-guided fine-needle aspiration for solid thyroid nodules with non-diagnostic cytology. All nodules were classified by TIRADS (categories 4a, 4b, 4c and 5), and elastography scores were assigned according to the Rago and Asteria criteria. The malignancy risks for TIRADS categories 4a, 4b, 4c and 5 were 12.5%, 25.0%, 25.8% and 16.7%, respectively. Elastography revealed the highest diagnostic performance for TIRADS category 4a, with a sensitivity, specificity, negative predictive value, positive predictive value and accuracy of 100%, 85.7%, 100%, 50% and 87.5% for the Asteria criteria. Observation may be considered for non-diagnostic solid nodules that have no other suspicious ultrasonographic features and are also benign on real-time strain elastography using the Asteria criteria.

Clinical application of sonoelastography in thyroid, prostate, kidney, pancreas, and deep venous thrombosis

This article reviews the clinical applications of current ultrasound elastography methods in non-hepatic conditions including thyroid nodules, prostate cancer, chronic kidney disease, solid renal lesions, pancreatic lesions, and deep vein thrombosis. Pathophysiology alters tissue mechanical properties via ultrastructural changes including fibrosis, increased cellularity, bleeding, and necrosis, creating a target biomarker, which can be imaged qualitatively or quantitatively with US elastography. US elastography methods can add information to conventional US methods and improve the diagnostic performance of conventional US in a range of disease processes.

Comparison of Diagnostic Accuracy of Real-Time Elastography and Shear Wave Elastography in Differentiation Malignant From Benign Thyroid Nodules

Thyroid nodules are relatively more prevalent in iodine-deficiency area, and the incidence increased sharply in the past decade in these areas. Workup of malignant from benign nodules in clinic was the main problem for managing thyroid nodules.An overall search for the articles about the diagnostic performance of real-time elastography (RTE) and shear wave elastography (SWE) before April 2015 in the databases of PubMed, Embase, and Google scholar. The pooled sensitivity, specificity, and summary receiver operating characteristic (SROC) curve were obtained from individual studies with a random-effects model. Subgroup and meta-regression analysis were also performed.Fifty-six studies involved in 2621 malignant nodules and 7380 benign nodules were contained in our meta-analysis. The pooled sensitivity and specificity of RTE was 83.0% and 81.2%, which is higher than SWE (sensitivity: 78.7%, specificity: 80.5%). The areas under the SROC curve of RTE and SWE were 0.885 and 0.842 respectively. RTE had higher diagnostic value for Caucasians than Asians. Stran ratio (SR) assessment had higher diagnostic performance than elasticity score (ES) system. Similarly, it had higher diagnostic value when malignant nodules were more than 50.In summary, the results revealed that RTE had higher diagnostic performance than SWE in differentiating malignant from benign nodules. However, future international multicenter studies in the region of thyroid risk need to further assess the diagnostic performance of RTE.

Acoustic Radiation Force Impulse Elastography: A Useful Tool for Differential Diagnosis of Thyroid Nodules and Recommending Fine-Needle Aspiration: A Diagnostic Accuracy Study

To investigate the diagnostic performance of combined use of conventional ultrasound (US) and elastography, including conventional strain elastography such as elasticity imaging (EI) and acoustic radiation force impulse (ARFI) elastography, and to evaluate their usefulness in recommending fine-needle aspiration (FNA).A total of 556 pathologically proven thyroid nodules were evaluated by US, EI, and ARFI examinations in this study. Three blinded readers scored the likelihood of malignancy for 4 datasets (ie, US alone, US and EI, US and virtual touch tissue imaging [VTI], and US and virtual touch tissue quantification [VTQ]). The diagnostic performances of 4 datasets in differentiating malignant from benign thyroid nodules were evaluated. The decision-making changes for FNA recommendation in the indeterminate nodules or the probably benign nodules on conventional US were evaluated after review of elastography.The diagnostic performance in terms of area under the ROC curve did not show any change after adding EI, VTI, or VTQ for analysis; and no differences were found among different readers; however, the specificity and positive predictive value (PPV) improved significantly after adding VTI or VTQ for analysis in the senior reader. For the indeterminate nodules on US that were pathologically benign, VTQ made correct decision-making changes from FNA biopsy to follow-up in a mean of 82.6% nodules, which was significantly higher than those achieved by EI (46.8%) and VTI (54.4%) (both P < 0.05). With regard to the probably benign nodules on US that were pathologically malignant, EI made the highest correct decision-making change from follow-up to FNA biopsy in a mean of 62.6% nodules (compared with 41.5% on VTQ, P < 0.05).The results indicated that ARFI increases the specificity and PPV in diagnosing thyroid nodules. US combined VTQ might be helpful in reducing unnecessary FNA for indeterminate nodules on US whereas US combined EI is useful to detect the false negative nodules that are probably benign on conventional US.

A Predictive Model for Selecting Malignant Thyroid Nodules in Patients With Nondiagnostic or Indeterminate Fine-Needle Aspiration Cytologic Findings

OBJECTIVES

The management of nodules with nondiagnostic or indeterminate fine-needle aspiration cytologic findings remains challenging. This study evaluated the clinical differences, conventional sonographic findings, elastographic findings, and cytologic findings for predicting thyroid malignancy.

METHODS

A total of 167 patients with a nondiagnostic or indeterminate thyroid fine-needle aspiration cytologic findings were enrolled in this study. The clinicopathologic and sonographic data from the patients were analyzed retrospectively to determine the independent predictive factors for thyroid malignancy. Then a scoring system was designed on the basis of statistically significant predictors.

RESULTS

Fine-needle aspiration cytologic findings, Thyroid Imaging Reporting and Data System categorization, and elastographic findings were independent predictive factors for thyroid cancer on multivariate analysis. The index points were statistically significant, with a score higher than 3 favoring malignant nodules with sensitivity of 79.37%, specificity of 85.85%, a positive predictive value of 76.9%, and a negative predictive value of 87.3%.

CONCLUSIONS

For patients with nondiagnostic or indeterminate fine-needle aspiration cytologic findings, our scoring system for prediction of thyroid malignancy can be another choice. We suggest surgery for nodules with index points higher than 3. For nodules with index points of 3 or lower, observation and regular follow-up are recommended.

Ultrasound elastography using carotid artery pulsation in the differential diagnosis of sonographically indeterminate thyroid nodules

OBJECTIVE. The purpose of this study was to evaluate the diagnostic performance of gray-scale ultrasound and a new method of thyroid ultrasound elastography using carotid artery pulsation in the differential diagnosis of sonographically indeterminate thyroid nodules. MATERIALS AND METHODS. A total of 102 thyroid nodules with indeterminate gray-scale ultrasound features from 102 patients (20 males and 82 females; age range, 16-74 years; mean age, 51 years) were included. The gray-scale ultrasound images of each nodule were reviewed and assigned a score from 1 (low) to 5 (high) according to the possibility of malignancy. Ultrasound elastography was performed using carotid pulsation as the compression source. The elasticity contrast index (ECI), which quantifies local strain contrast within a nodule, was automatically calculated. The radiologist reassessed the scores after concurrently reviewing gray-scale ultrasound and elastography. ROC curve analysis was used to evaluate the diagnostic performances of each dataset and to compare the AUC (Az) values of gray-scale ultrasound score alone, ECI alone, and a combined assessment. RESULTS. Significantly more malignant thyroid nodules were hypoechoic than benign nodules (p = 0.014). The ECI was significantly higher in malignant nodules than in benign thyroid nodules. The Az values of each dataset were 0.755 (95% CI, 0.660-0.835) for gray-scale ultrasound score, 0.835 (0.748-0.901) for ECI, and 0.853 (0.769-0.915) for a combined assessment. The Az value for a combined assessment of the gray-scale ultrasound score and the ECI was significantly higher than that for the gray-scale ultrasound score alone (p = 0.022). CONCLUSION. Combined assessment with gray-scale ultrasound and elastography using carotid artery pulsation is helpful for characterizing sonographically indeterminate thyroid nodules as benign or malignant.

Sonographic features of primary tumor as independent predictive factors for lymph node metastasis in papillary thyroid carcinoma

PURPOSE

The aim of this research was to find the sonographic features of primary tumor as independent predictive factors for lymph node metastasis in papillary thyroid carcinoma.

METHODS/PATIENTS

To facilitate the research, 514 patients with papillary thyroid carcinoma were divided into solitary and multifocal groups. In solitary group, thyroid lesions were divided into several subgroups by size, border, margin, echogenicity, echohomogeneity, calcification, vascularization, location, stiffness and Hashimoto's thyroiditis (HT) conditions. Then, univariable and multivariable analyses were performed to find the sonographic features of primary tumor as independent predictive factors for lymph node metastasis in papillary thyroid carcinoma.

RESULTS

A significant difference of lymph node metastasis rate was found between multifocal and solitary groups (P < 0.05). In univariable analysis, size, vascularization and coexistence of HT were found to be statistically significant factors (P = 0.004, 0.118, 0.016). Multivariable analysis revealed that lymph node metastasis rate was mainly associated with size [odds ratio (OR) = 1.690, 95 % confidence interval (CI) 1.157-2.469] and coexistence of HT (OR = 0.441, 95 % CI 0.219-0.888).

CONCLUSION

Preoperative sonographic features of primary tumor including the number, size and coexistence of HT were independent predictive factors for the state of cervical lymph node metastasis in patients with papillary thyroid carcinoma.

Thyroid nodule ultrasound: technical advances and future horizons

Thyroid nodules are extremely common and the vast majority are non-malignant; therefore the accurate discrimination of a benign lesion from malignancy is challenging. Ultrasound (US) characterisation has become the key component of many thyroid nodule guidelines and is primarily based on the detection of key features by high-resolution US. The thyroid imager should be familiar with the strengths and limitations of this modality and understand the technical factors that create and alter the imaging characteristics. Specific advances in high-resolution US are discussed with reference to individual features of thyroid cancer and benign disease. Potential roles for three-dimensional thyroid ultrasound and computer-aided diagnosis are also considered. The second section provides an overview of current evidence regarding thyroid ultrasound elastography (USE). USE is a novel imaging technique that quantifies tissue elasticity (stiffness) non-invasively and has potential utility because cancers cause tissue stiffening. In recent years, there has been much research into the value of thyroid USE for distinguishing benign and malignant nodules. Preliminary findings from multiple pilot studies and meta-analyses are promising and suggest that USE can augment the anatomical detail provided by high-resolution US. However, a definite role remains controversial and is discussed.

TEACHING POINTS

• High-resolution US characterises thyroid nodules by demonstration of specific anatomical features • Technical advances heavily influence the key US features of thyroid nodules • Most papillary carcinomas appear stiffer than benign thyroid nodules on US elastography (USE) • Thyroid USE is controversial because of variation in the reported accuracies for malignancy • Combined grey-scale US/USE may lower the FNAC rate in benign nodules.

Elastography Evaluation of Benign Thyroid Nodules in Patients Affected by Hashimoto's Thyroiditis

The aim of the present prospective study was to evaluate the predictive value of elastography in benign thyroid nodules of patients affected by Hashimoto's thyroiditis (HT). From January 2011 to January 2012, 242 nodules in patients affected by HT were submitted to fine needle aspiration cytology (FNAC). All of the patients underwent sonography and elastography performed before FNAC. 230 (95%) nodules were benign, 8 papillary cancers, and 4 follicular lesions. Score 1 was found in 79.1% of benign lesions (sensitivity 79.1%; specificity 66.7%; PPV 97.8%; NPV 14.3%; accuracy 78.5%; p < 0.05). In order to evaluate the outcome of thyroid ultrasound echogenicity in relation to elastography features of nodule(s), all the patients with benign nodules were stratified according to their hypoechoic pattern of thyroid (mild-moderate and severe). Following stratification score 1 was found in 84.2% of benign nodules (sensitivity 75.0%; specificity 88.9%; PPV 27.3%; NPV 98.4%; accuracy 88.2%; p < 0.0001) of patients with a mild-moderate ultrasound thyroid hypoechogenicity, whereas it was found in 60% of benign nodules (p = 0.715) of patients with a marked thyroid hypoechogenicity. Elastography appears to have limited value in detecting thyroid cancer in patients affected by Hashimoto's thyroiditis with severe hypoechoic thyroid tissue.

Elastography using multi-stream GPU: an application to online tracked ultrasound elastography, in-vivo and the da Vinci Surgical System

A system for real-time ultrasound (US) elastography will advance interventions for the diagnosis and treatment of cancer by advancing methods such as thermal monitoring of tissue ablation. A multi-stream graphics processing unit (GPU) based accelerated normalized cross-correlation (NCC) elastography, with a maximum frame rate of 78 frames per second, is presented in this paper. A study of NCC window size is undertaken to determine the effect on frame rate and the quality of output elastography images. This paper also presents a novel system for Online Tracked Ultrasound Elastography (O-TRuE), which extends prior work on an offline method. By tracking the US probe with an electromagnetic (EM) tracker, the system selects in-plane radio frequency (RF) data frames for generating high quality elastograms. A novel method for evaluating the quality of an elastography output stream is presented, suggesting that O-TRuE generates more stable elastograms than generated by untracked, free-hand palpation. Since EM tracking cannot be used in all systems, an integration of real-time elastography and the da Vinci Surgical System is presented and evaluated for elastography stream quality based on our metric. The da Vinci surgical robot is outfitted with a laparoscopic US probe, and palpation motions are autonomously generated by customized software. It is found that a stable output stream can be achieved, which is affected by both the frequency and amplitude of palpation. The GPU framework is validated using data from in-vivo pig liver ablation; the generated elastography images identify the ablated region, outlined more clearly than in the corresponding B-mode US images.

Elastographic techniques of thyroid gland: current status

Thyroid nodules are very common with malignancies accounting for about 5 %. Fine-needle biopsy is the most accurate test for thyroid cancer diagnosis. Elastography, a new technology directly evaluating the elastic property of the tissue, has been recently added to the diagnostic armamentarium of the endocrinologists as noninvasive predictor of thyroid malignancy. In this paper, we critically reviewed characteristics and applications of elastographic methods in thyroid gland. Elastographic techniques can be classified on the basis of the following: source-of-tissue compression (free-hand, carotid vibration, ultrasound pulses), processing time (real-time, off-line), stiffness expression (qualitative, semi-quantitative, or quantitative). Acoustic radiation force impulse and aixplorer shear wave are the newest and most promising quantitative elastographic methods. Primary application of elastography is the detection of nodular lesions suspicious for malignancy. Published data show a high sensitivity and negative predictive value of the technique. Insufficient data are available on the possible application of elastography in the differential diagnosis of indeterminate lesions and in thyroiditis. Elastography represents a noninvasive tool able to increase the performance of ultrasound in the selection of thyroid nodules at higher risk of malignancy. Some technical improvements and definition of more robust quantitative diagnostic criteria are required for assigning a definite role in the management of thyroid nodules and thyroiditis to elastography.

Diagnostic performance of ultrasound and ultrasound elastography with respect to physician experience

The aim of this study was to compare the diagnostic performance of gray-scale ultrasound (US), elastography and a combination of gray-scale ultrasound and elastography (US-E) in differentiating benign and malignant thyroid nodules with respect to the level of physician experience. Three hundred fifty-eight patients with 367 thyroid nodules who underwent both gray-scale US and elastography, from November 2011 to January 2012, were included in this study. The diagnostic performance of US performed by experienced and less experienced physicians was compared. Comparisons of the diagnostic performance of US, elastography and US-E were evaluated for each group separately. Of 367 nodules, 121 were malignant and 246 were benign. When we compared the diagnostic performance of the experienced and less experienced physician groups, specificity was statistically higher in the experienced physician group for both US alone (p = 0.001) and US-E (p = 0.048). However, the experienced and less experienced physician groups did not differ significantly on other measures of diagnostic performance, regardless of modality. For the experienced physicians, the specificity and positive predictive value US were 88.0% and 76.8%, respectively; both of them were significantly higher than the corresponding values for US-E. For the less experienced physicians, specificity was significantly higher on elastography (93.8%) than on US (71.4%) (p < 0.001). However, diagnostic performance did not differ significantly between US and US-E for the less experienced physicians. Experienced physicians had superior specificity compared with less experienced physicians. The diagnostic performance of elastography and US-E was inferior compared with that of US alone, irrespective of the level of experience of the physician.

Relative proportions of stromal to cellular components of pleomorphic adenomas: determination with shear wave elastography

OBJECTIVES

The purpose of this study was to evaluate whether the relative proportions of stromal to cellular components of pleomorphic adenomas have an effect on the shear elastic modulus determined by shear wave elastography (SWE).

METHODS

This study was approved by the Ethics Committee of our institution and performed between September 2011 and December 2012. Thirty-five patients who underwent surgery for a parotid mass were included in the study. The maximum shear elastic modulus of the mass was measured by SWE. Pleomorphic adenomas were histopathologically subdivided into stroma-poor, intermediate-stroma, and stroma-rich tumors based on the relative proportion of stromal to cellular components.

RESULTS

The maximum shear elastic modulus values of the pleomorphic adenomas ranged from 12.6 to 291.9 kPa (mean ± SD, 120.9 ± 92.8 kPa). The Friedman test revealed a statistically significant relationship between the stromal amount and maximum shear elastic modulus (P < .001). Stroma-poor adenomas (mean, 32.3 ± 27.7 kPa; range, 12.6-81.1 kPa) were softer on SWE than stroma-rich adenomas (mean, 174.1 ± 48.4 kPa; range, 92.7-217.2 kPa; P = .009). No such significant difference was detected between stroma-poor and intermediate-stroma tumors (mean, 146.3 ± 106.1 kPa; range, 19.1-291.9 kPa; P = .062) or between intermediate-stroma and stroma-rich tumors (P = .465).

CONCLUSIONS

Shear wave elastography depicts pleomorphic adenomas with a variable appearance, which is due to the relative proportions of stromal to cellular contents in the tumors.

Real-time ultrasound elastography for differentiation of benign and malignant thyroid nodules: a meta-analysis

OBJECTIVES

The clinical challenge of managing thyroid nodules nowadays is to diagnose the minority of malignant disease. Real-time ultrasound elastography, which can measure tissue elasticity, is used as a complement to conventional sonography for improving the diagnosis of thyroid tumors. There are 2 common criteria for evaluating an elastogram: the elasticity score and strain ratio. This meta-analysis was performed to expand on a previous meta-analysis to assess the diagnostic power of ultrasound elastography in differentiating benign and malignant thyroid nodules for elasticity score and strain ratio assessment.

METHODS

The MEDLINE, EMBASE, PubMed, and Cochrane Library databases up to January 31, 2013, were searched. The pooled sensitivity, specificity, and summary receiver operating characteristic curve were obtained from individual studies with a random-effects model. The extent and sources of heterogeneity were explored.

RESULTS

A total of 5481 nodules in 4468 patients for elasticity score studies and 1063 nodules in 983 patients for strain ratio studies were analyzed. The overall mean sensitivity and specificity of ultrasound elastography for differentiation of thyroid nodules were 0.79 (95% confidence interval [CI], 0.77-0.81) and 0.77 (95% CI, 0.76-0.79) for elasticity score assessment and 0.85 (95% CI, 0.81-0.89) and 0.80 (95% CI, 0.77-0.83) for strain ratio assessment, respectively. The areas under the curve for the elasticity score and strain ratio were 0.8941 and 0.9285.

CONCLUSIONS

These results confirmed those obtained in the previous meta-analysis. Ultrasound elastography has high sensitivity and specificity for identification of thyroid nodules. It is a promising tool for reducing unnecessary fine-needle-aspiration biopsy.

Ultrasound elastography for thyroid nodules: recent advances

Ultrasonography (US)-based elastography has been introduced as a noninvasive technique for evaluating thyroid nodules that encompasses a variety of approaches such as supersonic shear imaging and acoustic radiation force impulse imaging as well as real-time tissue elastography. However, the diagnostic performances for differentiating malignant thyroid nodules from benign ones with elastography as an adjunctive tool of gray-scale US is still under debate. In this review article, diagnostic performances of conventional US and a combination of conventional US and elastography are compared according to the type of elastography. Further, the interobserver variability of elastography is presented according to the type of elastography.

Comparison of elastographic strain index and thyroid fine-needle aspiration cytology in 631 thyroid nodules

CONTEXT

Ultrasound (US) elastography (USE) was recently been reported as a sensitive, noninvasive tool for identifying thyroid cancer. However, the accuracy of this technique is hampered by the intra- and interoperator variability, some US features of the nodule, and the coexistence of autoimmune thyroid disease (ATD).

OBJECTIVES

The purpose of this article was to assess the accuracy of USE findings in the differential diagnosis of thyroid nodules compared with other US features to evaluate its feasibility in the presence of ATDs and identify the strain index (SI) cutoff with the highest diagnostic performance.

DESIGN

We evaluated 528 consecutive patients for a total of 661 thyroid nodules. All nodules underwent fine-needle aspiration cytology (FNAC) and USE evaluation. The SI was calculated as a ratio of the nodule strain divided by the strain of the softest part of the surrounding normal tissue.

RESULTS

The median SI value was significantly higher in THY4 and THY5 than in THY2 nodules in ATD-positive, ATD-negative, and ATD-unknown patients. The cutoff of SI for malignancy was estimated to be 2.905 by receiver operating characteristic curve analysis in a screening set (379 FNAC results), and then tested in a replication set (252 FNAC results). In all cases, a SI value of ≥ 2.905 conferred to the nodule a significantly greater probability of being malignant. This SI cutoff had the greatest area under the curve, sensitivity, and negative predictive value, compared with the conventional US features of malignancy.

CONCLUSION

The elastographic SI has a high sensitivity, specificity, and negative predictive value for the diagnosis of thyroid malignancy both in the presence and in the absence of ATD. If our data on USE are also confirmed in THY3 nodules, FNAC could be avoided in a number of thyroid nodules with certain features.