Ultrasound elastography in the head and neck. Part I. Basic principles and practical aspects

Soft tissue elasticity at teeth and implant sites. A novel outcome measure of the soft tissue phenotype

AIM

To assess ultrasonographic tissue elasticity at teeth and implant sites and its variation after peri-implant soft tissue augmentation with a connective tissue graft (CTG).

METHODS

Twenty-eight patients, each contributing with one clinically healthy dental implant exhibiting a soft tissue dehiscence (PSTD), were included. Implant sites were augmented with CTG and monitored over 12 months. Ultrasonographic strain elastography, expressed as strain ratios (SR1, SR2, and SR3, respectively) was assessed at baseline, 6-, and 12-month, and compared with the corresponding contralateral homologous natural tooth. SR1 assessed the strain/elasticity of the midfacial coronal portion of the soft tissue in comparison to the natural tooth crown/implant-supported crown, SR2 evaluated the strain of the midfacial coronal soft tissue in relation to the one of the alveolar mucosa, while SR3 depicted the strain of the midfacial soft tissue in relation to the interproximal soft tissue on the transverse ultrasound scan.

RESULTS

SR1 in natural dentition and at implant sites was 0.20 ± 0.08 and 0.30 ± 0.14, respectively (p = .002), indicating that the coronal portion of the soft tissue around teeth is generally more elastic than its counterpart around dental implants. Soft tissue augmentation with CTG promoted an increased stiffness of the midfacial coronal portion of the soft tissue over 12 months (p < .001 for SR1, SR2, and SR3). Strain ratios at the 12-month time points were significantly higher than the values observed at 6 months (p < .001). Regression analysis demonstrated that strain elastography ratios in natural dentition were significantly associated with keratinized gingiva width, and gingival thickness. At implant sites, SR1 was significantly associated with keratinized mucosa width and mucosal thickness (p < .001 for both correlations), SR2 was significantly associated with keratinized mucosa width (p = .013), and SR3 was significantly associated with the surgical technique performed in combination with CTG (p = .022).

CONCLUSION

Ultrasound strain elastography captures and quantifies tissue elasticity and its changes after soft tissue augmentation. A different baseline tissue elasticity was observed between teeth and dental implants in the most coronal aspect of the soft tissue. The main factors affecting tissue elasticity-related outcomes were the keratinized tissue width, and mucosal thickness.

Ultrasound elastography in dogs: Physical principles and application in intestinal evaluation

Ultrasound elastography provides diagnostic information based on tissue elasticity. There is a lack of specific studies on the application of elastography in canine intestinal assessment. Therefore, we reviewed comparative medicine studies and those referring to the literature listed in the databases. Static and dynamic elastography techniques are widely applied in human intestinal diseases, especially Chron's disease, but few studies have investigated the application of these modalities in canine enteropathies. This case raises questions about the use of new diagnostic imaging techniques in veterinary gastroenterology and highlights the need for further research. Hence, this study aimed to review the literature on the physical principles of elastography and its clinical application in the intestinal evaluation of dogs.

Determining the elastography strain ratio cut off value for differentiating benign from malignant breast lesions: systematic review and meta-analysis

Background

Elastography is an addition to grey-scale ultrasonic examination that has gained substantial traction within the last decade. Strain ratio (SR) has been incorporated as a semiquantitative measure within strain elastography, thus a potential imaging biomarker. The World Federation for Ultrasound in Medicine and Biology (WFUMB) published guidelines in 2015 for breast elastography. These guidelines acknowledge the marked variance in SR cut-off values used in differentiating benign from malignant lesions. The objective of this review was to include more recent evidence and seek to determine the optimal strain ratio cut off value for differentiating between benign and malignant breast lesions.

Methods

Comprehensive search of MEDLINE and Web of Science electronic databases with additional searches via Google Scholar and handsearching set from January 2000 to May 2020 was carried out. For retrieved studies, screening for eligibility, data extraction and analysis was done as per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses for Diagnostic Test Accuracy (PRISMA-DTA) Statement guidelines of 2018. Quality and risk of bias assessment of the studies were performed using the revised Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool.

Results

A total of 424 articles, 412 from electronic database and 12 additional searches were retrieved and 65 studies were included in the narrative synthesis and subgroup analysis. The overall threshold effect indicated significant heterogeneity among the studies with Spearman correlation coefficient of Logit (TPR) vs Logit (FPR) at − 0.301, p-value = 0.015. A subgroup under machine model consisting seven studies with 783 patients and 844 lesions showed a favourable threshold, Spearman’s correlation coefficient,0.786 (p = 0.036).

Conclusion

From our review, currently the optimal breast SR cut-off point or value remains unresolved despite the WFUMB guidelines of 2015. Machine model as a possible contributor to cut-off value determination was suggested from this review which can be subjected to more industry and multi-center research determination.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40644-022-00447-5.

Evaluation of acoustic radiation force impulse imaging in differentiating benign and malignant cervical lymphadenopathy

Background:

The aim of this study was to assess the diagnostic role of acoustic radiation force impulse imaging (ARFI) in differentiating benign and malignant cervical nodes.

Methods:

This was a diagnostic accuracy cross-sectional study. All patients who underwent ultrasound-guided fine-needle aspiration cytology (FNAC) of cervical nodes were included. Patients without FNAC/biopsy and patients in whom cervical nodes were cystic or completely necrotic were excluded. FNAC was used as reference investigation to predict the diagnostic accuracy. In all cases, FNAC was carried out after the B-mode, color Doppler and the ARFI imaging. In patients with multiple cervical lymph nodes, the most suspicious node based on grayscale findings was chosen for ARFI. ARFI included Virtual Touch imaging (VTI), area ratio (AR), and shear wave velocity (SWV) for each node, and the results were compared with FNAC/biopsy.

Results:

The final analysis included 166 patients. Dark VTI elastograms had sensitivity and specificity of 86.2% and 72.1%, respectively, in identifying malignant nodes. Sensitivity and specificity of AR were 71.3% and 82.3%, respectively, for a cutoff of 1.155. Median SWV of benign and malignant nodes was 1.9 [95% confidence interval (CI), 1.56–2.55] m/s and 6.7 (95% CI, 2.87–9.10) m/s, respectively. SWV >2.68 m/s helped in identifying malignant nodes with 81% specificity, 81.6% sensitivity, and 81.3% accuracy. ARFI was found to be inaccurate in tuberculous and lymphomatous nodes.

Conclusion:

Malignant nodes had significantly darker elastograms, higher AR and SWV compared to benign nodes, and SWV was the most accurate parameter. ARFI accurately identifies malignant nodes, hence could potentially avoid unwarranted biopsy.

What does liver elastography measure? Technical aspects and methodology

Elastography can be thought as an extension of the ancient technique of palpation. After giving a short introduction to the history of elastography, the different technologies that are nowadays available and the physics behind them, the article focuses on the assessment of liver stiffness in patients with diffuse liver disease using shear wave elastography (SWE). Practical advices on how to perform the SWE techniques and on the factors that should be considered for a correct interpretation of the results are given. This paper aimed to provide a practical guide for beginners and advanced clinical users to better understand technical aspects, methodologies and terminology.

Effectiveness of ultrasonography and shear wave sonoelastography in Sjögren syndrome with salivary gland involvement

Purpose

This study investigated the effectiveness of major salivary gland ultrasonography (MSGUS) using a new grading system and shear wave elastography (SWE) in evaluating the major salivary glands of patients with Sjögren syndrome (SjS).

Methods

This prospectively-designed cross-sectional study included 49 SjS patients and 49 healthy controls. Major salivary glands were examined with gray-scale ultrasonography and SWE. A new grading system for salivary glands was developed using MSGUS findings. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of MSGUS and shear wave velocity (SWV) values were investigated. The MSGUS grading system and SWV values were evaluated together by logistic regression analysis. A cutoff value of SWE for salivary glands was determined.

Results

The sensitivity, specificity, PPV, and NPV of MSGUS were 69.4%, 73.5%, 72.3%, and 70.6% for the submandibular gland and 69.4%, 65.3%, 66.7%, and 68.1% for the parotid gland, respectively. The mean SWV values of the parotid and submandibular glands were significantly higher in SjS patients than in controls (P<0.05). The sensitivity, specificity, PPV, and NPV for the submandibular gland (cutoff, 1.95 m/s) and the parotid gland (cutoff, 2.39 m/s) were 69.4%, 52%, 59.1%, and 63% and 82.7%, 83.7%, 83.5%, and 82.8%, respectively. Adding SWE to the parotid gland grading system increased the sensitivity and specificity (sensitivity, 82.7%; specificity, 83.7%).

Conclusion

Evaluating the salivary glands using MSGUS with a new grading system and SWE may contribute to the diagnosis of SjS. The combination of MSGUS and SWE may be a promising tool for diagnosing SjS.

Ultrasonographic Algorithm for the Assessment of Sentinel Lymph Nodes That Drain the Mammary Carcinomas in Female Dogs

The status of sentinel lymph nodes (SLNs) is decisive in staging, prognosis, and therapeutic approach. Using an ultrasonographic examination algorithm composed of B-mode, Doppler technique, contrast-enhanced ultrasound (CEUS) and elastography, this study aimed to determine the diagnostic performance of the four techniques compared to histopathological examination. 96 SLNs belonging to 71 female dogs with mammary gland carcinomas were examined. After examinations, mastectomy and lymphadenectomy were performed. Histopathological examination confirmed the presence of metastases in 54 SLNs. The elasticity score had the highest accuracy-89.71%, identifying metastases in SLNs with 88.9.9% sensitivity (SE) and 90.5% specificity (SP), ROC analysis providing excellent results. The S/L (short axis/long axis) ratio showed 83.3% SE and 78.6% SP as a predictor of the presence of metastases in SLN having a good accuracy of 81.2%. On Doppler examination, the resistivity index(RI) showed good accuracy of 80% in characterizing lymph nodes with metastases versus unaffected ones; the same results being obtained by CEUS examination. By assigning to each ultrasonographic parameter a score (0 or 1) and summing up the scores of the four techniques, we obtained the best diagnostic performance in identifying lymph node metastases with 92.2% accuracy. In conclusion, the use of the presented algorithm provides the best identification of metastases in SLNs, helping in mammary carcinoma staging and appropriate therapeutic management.

Ultrasound Elastography for Lung Disease Assessment

Ultrasound elastography (US-E) is a noninvasive, safe, cost-effective and reliable technique to assess the mechanical properties of soft tissue and provide imaging biomarkers for pathological processes. Many lung diseases such as acute respiratory distress syndrome, chronic obstructive pulmonary disease, and interstitial lung disease are associated with dramatic changes in mechanical properties of lung tissues. Nevertheless, US-E is rarely used to image the lung because it is filled with air. The large difference in acoustic impedance between air and lung tissue results in the reflection of the ultrasound wave at the lung surface and, consequently, the loss of most ultrasound energy. In recent years, there has been an increasing interest in US-E applications in evaluating lung diseases. This article provides a comprehensive review of the technological advances of US-E research on lung disease diagnosis. We introduce the basic principles and major techniques of US-E and provide information on various applications in lung disease assessment. Finally, the potential applications of US-E to the diagnosis of COVID-19 pneumonia is discussed.

B-mode ultrasound, color Doppler, and sonoelastography in differentiation between benign and malignant cervical lymph nodes with special emphasis on sonoelastography

Background

Enlarged cervical lymph nodes are the most commonly encountered neck lumps. Ultrasonography is the most extensively used tool for classification of superficial lymph nodes due to its availability and low cost. Ultrasound (US) elastography refers to a non-invasive imaging technique that can describe tissue displacement (i.e., strain) or stiffness in response to a given force.

The aim of this study is to compare between B-mode sonography, color Doppler, and sonoelastography in assessment of enlarged deep cervical lymph nodes.

Results

The prevalence of benign lymph nodes was 26 out of 84 (31%). Lymphomatous lymph nodes were 22/84 (26.2%), while metastatic lymph nodes were 36/84 (42.8%). Color Doppler evaluation of nodal vascular pattern was of high sensitivity (91.7%), specificity (80.8%), and accuracy (88.6%) for differentiating metastatic and benign nodes (P value was < 0.001). There was a significant difference between elasticity scores of benign and malignant lymph nodes (P < 0.001). The most frequent score in the malignant group was 3 (21/27) (77.8%) while the most frequent score in the benign group was 2 (5/11) (45.5%). The mean strain ratio (strain index) for malignant lymph nodes (mean 3.2 ± 0.8) was significantly greater than that for benign lymph nodes (mean 1.1 ± 0.8).

Conclusion

Ultrasound elastography with its high sensitivity and specificity is a helpful improvement in US for the assessment of cervical lymph nodes, in which biopsies should be performed.

Thyroglossal duct cysts and site-specific differential diagnoses: imaging findings with emphasis on ultrasound assessment

Thyroglossal duct cysts (TGDCs) are the most common congenital abnormality of the neck, accounting for approximately 70% of congenital neck lesions. Two-thirds of thyroglossal duct anomalies are diagnosed within the first three decades of life, with more than half being identified before 10 years of age. The age of presentation, clinical examination and imaging are essential for an accurate diagnosis. This review aims to summarize the imaging findings of TGDCs and their main differential diagnoses with emphasis on ultrasound assessment. A focus on site-specific key differentiating between them is also addressed.

Enhanced Instantaneous Elastography in Tissues and Hard Materials Using Bulk Modulus and Density Determined Without Externally Applied Material Deformation

Ultrasound is a continually developing technology that is broadly used for fast, non-destructive mechanical property detection of hard and soft materials in applications ranging from manufacturing to biomedical. In this study, a novel monostatic longitudinal ultrasonic pulsing elastography imaging method is introduced. The existing elastography methods require an acoustic radiational or dynamic compressive externally applied force to determine the effective bulk modulus or density. This new, passive M-mode imaging technique does not require an external stress and can be effectively used for both soft and hard materials. Strain map imaging and shear wave elastography are two current categories of M-mode imaging that show both relative and absolute elasticity information. The new technique is applied to hard materials and soft material tissue phantoms for demonstrating effective bulk modulus and effective density mapping. When compared with standard techniques, the effective parameters fall within 10% of standard characterization methods for both hard and soft materials. As neither the standard A-mode imaging technique nor the presented technique require an external applied force, the techniques are applied to composite heterostructures and the findings presented for comparison. The presented passive M-mode technique is found to have enhanced resolution over standard A-mode modalities.

The effect of regions-of-interest and elasticity modulus selection on differentiating benign and malignant cervical lymph nodes with shear wave elastography

OBJECTIVE

Imaging diagnosis of cervical lymphadenopathy has conventionally used ultrasonography. Shear wave elastography (SWE) is a recent ultrasound technological advancement that has shown promise in the important medical problem of differentiating between benign and malignant cervical lymph nodes based on quantitative measurements of elasticity modulus. However, widely varying elasticity modulus metrics and regions-of-interest (ROIs) were used in existing studies, leading to inconsistent findings and results that are hard to compare with each other.

METHODS

Using a large dataset of 264 cervical lymph nodes from 200 patients, we designed a study comparing three elasticity modulus metrics (Emax, Emean, and standard deviation-SD) with three different ROIs to evaluate the effect of such selections. The metric values were compared between the benign and malignant node groups. The different ROI and metric selections were also compared through receiver operating characteristics curve analysis.

RESULTS

For all ROIs, all metric values were significantly different between the two groups, indicting their diagnostic potential. This was confirmed by the ≥0.80 area under the curve (AUC) values achieved with these metrics. Different ROIs had no effect on Emax, whereas all ROIs achieved high performance at 0.88 AUC. For Emean, the smallest ROI focusing on the area of the highest elasticity achieved the best diagnostic performance. In contrast, the larger ROIs achieved higher performances for SD.

CONCLUSIONS

This study illustrated the effect of elasticity modulus and ROI selection on the diagnostic performance of SWE on cervical lymphadenopathy. These new findings help guide relevant future studies and clinical applications of this important quantitative imaging modality.

Strain and shear wave ultrasound elastography in evaluation of chronic inflammatory disorders of major salivary glands

OBJECTIVE

The aim of this study was to assess chronic inflammatory conditions of major salivary glands by ultrasound elastography.

METHODS

21 patients with chronic inflammatory conditions of major salivary glands and 21 healthy adult volunteers were included in this study. All participants underwent B-mode sonography and ultrasound elastography. The diagnostic performance of strain ratio and shear wave velocity was evaluated by sensitivity and specificity at the optimum cutoff point and the area under the receiver operating characteristic curve.

RESULTS

Cases showed statistically significant higher median strain ratio of parotid and submandibular gland than control group (p-value = 0.001). Total cases showed statistically significant higher median scores than control group (p-value < 0.001). At cut-off value of (1.13); diagnostic accuracy, sensitivity and specificity were 97.6, 95.2 and 100% respectively with AUROC 0.954 and confidence interval: 0.840-0.995. Cases showed statistically significant higher median shear wave velocity of parotid gland than control group (p-value = 0.022), with no statistically significant difference in submandibular gland in the two groups (p-value = 0.216). Total cases showed statistically significant higher median scores than control group (p-value < 0.001). At cut-off value of (23.5), diagnostic accuracy was 78.6% with a sensitivity of 81% and specificity of 76.2% with 0.819 AUROC and onfidence interval :0.669-0.920.

CONCLUSION

Our initial experience suggests that elastography may be potentially useful for diagnosis of chronic inflammatory conditions of the major salivary glands. This conclusion needs to be further validated large sample studies.

Ultrasound elastography as a potential diagnostic aid in oral submucous fibrosis

Background

Oral submucous fibrosis (OSMF) is a well-recognized "potentially malignant" disorder. It mostly affects the productive population of young adults and adolescents. The diagnosis of oral submucous fibrosis is primarily clinical and subjective. The only objective diagnostic method for OSMF is tissue biopsy. This study was conducted to find the potential use of ultrasound elastography to objectively quantify the clinical presentation in accordance with severity of the clinical condition in OSMF.

Materials and Methods

The study sample consisted of 27 clinically diagnosed and staged participants with OSMF. Transcutaneous ultrasonography was done by a single operator on GE Logiq E9 machine with a 6-15 MHz linear matrix probe. Color-coded scheme was used to qualitatively grade the eight different zones of oral mucosa with the use of stress-strain elastography. The grades ranged from 0 to 5, where 0 represented artifacts and color range from red to blue corresponded to varying degree of increasing tissue stiffness. Clinical stage 1, 2, and 3 corresponded to mouth opening of >30 mm, 20-30 mm, and <20 mm, respectively. The summative elastography score range as follows: 8-10, 11-14, and ≥15 represented the respective degree of tissue stiffness from soft, mild stiff to severe stiff.

Results

The results obtained by Pearson's correlation between the elastographic grading and clinical grading came out to be 0.007, and it was highly significant. The sensitivity and specificity of the diagnostic method were 90.9% and 20%, respectively.

Conclusion

The advantages of ultrasound elastography as a diagnostic tool over the subjective clinical method of diagnosis and staging of OSMF looks promising. Further studies should be conducted with a suitable specific transducer probe and with quantitative diagnostic elastography method.

Masseter muscle thickness and elasticity in periodontitis

This study aimed to compare the thickness and elasticity of the masseter muscle between patients with gingivitis and patients with periodontitis. A total of 124 patients (63 gingivitis, 61 chronic periodontitis) were recruited at the start of the study, but only 84 patients were declared as final participants. Patients were divided into two groups: (1) patients suffering from gingivitis and (2) those with generalized chronic periodontitis. Clinical (PI, plaque index; GI, gingival index; PD, probing depth; CAL, clinical attachment loss; and BOP, bleeding on probing scores) and ultrasonographic (thickness and elasticity of the masseter muscle) measurements of periodontitis were performed. There were no significant differences in gender, age, body mass index, education status, income level, or marital status between the two groups (P > 0.05). The mean age ± SD for the gingivitis and periodontitis groups was 39.5 ± 10.8 years and 44.8 ± 8.8 years, respectively. There were significant differences between the two groups in the number of PI, GI, PD, CAL, and BOP scores. There were significant differences between the two groups when thickness of masseter during contraction and at rest was taken into account. The gingivitis group had significantly thicker masseter during both contraction and rest. On the other hand, when the elasticity of the masseter was evaluated, there were no significant differences found between the two groups and two sides for each group. Masseter muscle thickness in the periodontitis group was found to be decreased compared with that in the gingivitis group. Furthermore, loss of periodontal tissues due to periodontitis reduces the masticatory ability.

The Role of Real-Time Elastography in the Differential Diagnosis of Salivary Gland Tumors

OBJECTIVES

The aim of the study was to scrutinize the value of qualitative elastography in the diagnosis of salivary gland masses.

METHODS

Sixty patients were enrolled in this prospective study. Patients aged between 1 and 91 years (mean age, 48.8 ± 20.48) with a salivary gland mass were studied with real-time elastography. All patients were examined by 1 examiner, blinded to all relevant data. On elastography, masses were scored into 4 types according to their stiffness compared to normal tissue. Scores of 3 and 4 were accepted as signs of malignancy. Sensitivity, specificity, and positive and negative predictive value were calculated for elastography in verifying malignancy.

RESULTS

Forty-two percent of the masses were located in the parotid, and the rest in submandibular gland. The diameter of the lesions varied between 12 and 60 mm (mean, 24.36 ± 11.98 mm). Forty-four masses were benign (73%), and among them the majority were inflammatory lesions (31 of 60; 51.7%). There were 16 malignant lesions (27%). On elastography, not only all malignant lesions but 15 benign lesions were scored as 3 to 4. All masses scored as 1 to 2 were benign. Sensitivity was 100%; specificity, 66%; positive predictive value, 52%; and negative predictive value, 100%. When only Score 4 lesions were accepted as malignant, these values became 75%, 77%, 55%, and 90%, respectively.

CONCLUSIONS

Elastography alone cannot be used to discriminate malignant from benign in the evaluation of salivary gland lesions. However, with its high negative predictive value, it may be used as an adjunct tool to increase the diagnostic value of ultrasonography.

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.

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.

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.

Ultrasound Elastography: Review of Techniques and Clinical Applications

Elastography-based imaging techniques have received substantial attention in recent years for non-invasive assessment of tissue mechanical properties. These techniques take advantage of changed soft tissue elasticity in various pathologies to yield qualitative and quantitative information that can be used for diagnostic purposes. Measurements are acquired in specialized imaging modes that can detect tissue stiffness in response to an applied mechanical force (compression or shear wave). Ultrasound-based methods are of particular interest due to its many inherent advantages, such as wide availability including at the bedside and relatively low cost. Several ultrasound elastography techniques using different excitation methods have been developed. In general, these can be classified into strain imaging methods that use internal or external compression stimuli, and shear wave imaging that use ultrasound-generated traveling shear wave stimuli. While ultrasound elastography has shown promising results for non-invasive assessment of liver fibrosis, new applications in breast, thyroid, prostate, kidney and lymph node imaging are emerging. Here, we review the basic principles, foundation physics, and limitations of ultrasound elastography and summarize its current clinical use and ongoing developments in various clinical applications.

Real-Time Sonoelastography of Parotid Gland Tumors

OBJECTIVES

We sought to determine the performance of real-time sonoelastography in the differential diagnosis of parotid gland tumors.

METHODS

Between April, 2014, and June, 2015, 54 parotid gland masses were examined by ultrasound and strain sonoelastography in 46 patients. Real-time sonoelastography using the elasticity score (E-index), which gives an absolute value between 0 (softest) and 6 (hardest), was performed. Demographic characteristics, histopathologic examination, and difference in elasticity scores between benign and malignant masses were evaluated.

RESULTS

The mean age of the patients was 60.01 ± 2.97 years, and 56.52% of the patients were male (n = 26). Among the 54 parotid gland masses, 44 (81.5%) were benign and 10 (18.5%) were malignant tumors, 63% (n = 34) of the lesions being on the right side. The diagnoses as benign tumors consisted of Warthin tumor (n = 18, 33.3%), pleomorphic adenoma (n = 8, 14.8%) and other benign tumors (n = 18, 33.3%). The mean elasticity score and the size of all tumors were 2.87 ± 0.96 and 23.68 ± 12.38 mm, respectively. The mean elasticity score for benign tumors was 2.75 ± 0.95, and for malignant tumors it was 3.44 ± 0.85 (P = .034).

CONCLUSIONS

According to our results, real-time strain sonoelastography seems to have additional value over routine sonographic evaluation of parotid gland tumors in the differential diagnosis of benign and malignant parotid masses. However, with a small sample of malignant cases and appreciable overlap of the stiffness of benign and malignant masses, caution must be applied because the findings may not be representative of all patients with a parotid gland tumor.

Placental Elasticity and Histopathological Findings in Normal and Intra-Uterine Growth Restriction Pregnancies Assessed with Strain Elastography in Ex Vivo Placenta

The aim of this study was to investigate the differences of placental elasticity between intra-uterine growth restriction (IUGR) and normal pregnancies to show whether or not there is any association between histopathological changes and placental elasticity. Fifty-five human placentas were collected at delivery, including 25 with IUGR and 30 controls. Strain elastography (SE) was performed ex vivo and all placentas were examined histopathologically. Elasticity index (EI) and histopathological findings were compared between groups. The placental stiffness and presence of histopathological changes were higher in the IUGR group than in controls (p < 0.05). Also, histopathological findings were associated with decreased EI values, but no specific patterns of histologic abnormalities were identified except villitis and delayed villous maturity. Distinct reduced placental elasticity could be the result of the cumulative effects of all the histologic findings in IUGR.

Applicability of shear wave elastography of the major salivary glands: values in healthy patients and effects of gender, smoking and pre-compression

Our aim in this study was to determine normal shear wave elastography (SWE) values for the parenchyma of the major salivary glands and to evaluate the influences of gender, smoking, side and type of gland and varying amounts of ultrasound probe pressure on SWE values. Twenty-five consecutive healthy patients were examined with ultrasound. SWE velocities were measured with acoustic radiation force imaging in the hilum and central region of both glands with "normal" and very low pressure. Mean SWE velocities were 1.854 m/s for the parotid gland and 1.932 m/s for the submandibular gland. No statistically significant differences were detected between males and females, smokers and non-smokers, parotid and submandibular gland and left and right sides. Greater pre-compression with the ultrasound probe resulted in a statistically significant increase in the SWE values of both salivary glands (p < 0.000). The degree of pre-compression by the ultrasound transducer should be standardized, so that the reliability and reproducibility of this innovative method can be improved.

Ultrasound elastography for evaluation of cervical lymph nodes

Ultrasound (US) elastography has been introduced as a noninvasive imaging technique for evaluating cervical lymph nodes. US elastography techniques include strain elastography and shear wave-based elastography. The application of this technique is based on the fact that stiff tissues tend to deform less and show less strain than compliant tissues when the same force is applied. In general, metastatic lymph nodes demonstrate higher stiffness than benign lymph nodes. Overall, preliminary studies suggest that US elastography may be useful in differentiating benign and malignant cervical lymph nodes, thereby informing decisions to perform a biopsy and facilitating follow-up. For US elastography to be accepted into clinical practice, however, its techniques, associated diagnostic criteria, and reliability need to be further refined.

Effects of compression force on elasticity index and elasticity ratio in ultrasound elastography

OBJECTIVES

The purpose of this study was to investigate the relationship between compression force and hardness values in ultrasound elastography.

METHODS

Ultrasound elastography was performed using an elastography phantom, comprising inclusions with different elasticities and echogenicities. The compression force was set to approximately 100 gw (light force) and approximately 500 gw (heavy force). The elasticity index (EI) of the inclusion was measured. The EI was a relative hardness value of a structure within an elastographic image. Similarly, the EI of the background was measured as a reference. The elasticity ratio (ER) was calculated as the EI of the inclusion divided by the EI of the reference.

RESULTS

The hardness of the phantom could be discerned with both the EI and ER, regardless of the compression force. The EI and ER with heavy force tended to be higher than those with light force, but the difference was not significant. A strong correlation was observed between the EI and ER of soft structures, whereas the correlation between the EI and ER of hard structures was weak, and the ER values varied widely.

CONCLUSIONS

The EI offers potential as a good indicator for assessing the hardness.