Reproducibility of Acoustic Radiation Force Impulse Imaging in Thyroid and Salivary Glands with Experienced and Inexperienced Examiners

Differentiation of salivary gland tumours using diffusion-weighted image-based virtual MR elastography: a pilot study

OBJECTIVES

Differentiation among benign salivary gland tumours, Warthin tumours (WTs), and malignant salivary gland tumours is crucial to treatment planning and predicting patient prognosis. However, differentiation of those tumours using imaging findings remains difficult. This study evaluated the usefulness of elasticity determined from diffusion-weighted image (DWI)-based virtual MR elastography (MRE) compared with conventional magnetic resonance imaging (MRI) findings in differentiating the tumours.

METHODS

This study included 17 benign salivary gland tumours, 6 WTs, and 11 malignant salivary gland tumours scanned on neck MRI. The long and short diameters, T1 and T2 signal intensities, tumour margins, apparent diffusion coefficient (ADC) values, and elasticity from DWI-based virtual MRE of the tumours were evaluated. The interobserver agreement in measuring tumour elasticity and the receiver operating characteristic (ROC) curves were also assessed.

RESULTS

The long and short diameters and the T1 and T2 signal intensities showed no significant difference among the 3 tumour groups. Tumour margins and the mean ADC values showed significant differences among some tumour groups. The elasticity from virtual MRE showed significant differences among all 3 tumour groups and the interobserver agreement was excellent. The area under the ROC curves of the elasticity were higher than those of tumour margins and mean ADC values.

CONCLUSION

Elasticity values based on DWI-based virtual MRE of benign salivary gland tumours, WTs, and malignant salivary gland tumours were significantly different. The elasticity of WTs was the highest and that of benign tumours was the lowest. The elasticity from DWI-based virtual MRE may aid in the differential diagnosis of salivary gland tumours.

Influence of transducer pressure and examiner experience on muscle active shear modulus measured by shear wave elastography

INTRODUCTION

This study examined the effects of ultrasound transducer pressure and examiner experience on the biceps femoris long head and semitendinosus muscle active shear modulus in healthy individuals (n = 28).

METHODS

Active shear modulus was assessed using shear wave elastography at 20% of knee flexor maximal voluntary isometric contraction. Examiners with different experience levels measured the muscles' shear modulus with three pressure levels: mild, moderate, and hard.

RESULTS

A main effect of transducer pressure was found for both biceps femoris long head (p < 0.001; η2p = 0.314) and semitendinosus muscles (p < 0.001; η2p = 0.280), whereas differences were found between mild-moderate (biceps femoris long head: p = 0.013, d = 0.23; semitendinosus: p = 0.024, d = 0.25), and mild-hard pressures (biceps femoris long head: p = 0.001, d = 0.47; semitendinosus: p = 0.002, d = 0.47). Examiners performed similar shear modulus measurements in the biceps femoris long head (p = 0.299; η2p = 0.041) and semitendinosus (p = 0.177; η2p = 0.066), although the experienced examiner showed a higher measurement repeatability (biceps femoris long head: ICC = 0.86-0.95, semitendinosus: ICC = 0.89-0.96; vs. biceps femoris long head: ICC = 0.78-0.87, semitendinosus: ICC = 0.66-0.87).

CONCLUSION

Transducer pressure influences the active shear modulus measurement between mild and moderate or hard pressures. Additionally, examiner experience seems to have no influence on muscle active shear modulus measurement when assessed at the same site (using casts).

IMPLICATIONS FOR PRACTICE

Future studies assessing active muscle shear modulus should use mild transducer pressure and having experienced examiners in order to improve measurement reliability.

Combining surface-enhanced Raman scattering (SERS) of saliva and two-dimensional shear wave elastography (2D-SWE) of the parotid glands in the diagnosis of Sjögren's syndrome

In this study, we combine the molecular structural information gained by SERS of saliva samples with the morphological data given by two-dimensional shear wave elastography (2D-SWE) (SuperSonic Imagine, Aixplorer) of parotid glands in the case of n = 31 patients with Sjögren's syndrome (SjS) and n = 22 controls, with the aim to discriminate between the two groups. The overall classification accuracy yielded by a hybrid principal component analysis-linear discriminant analysis (PCA-LDA) model based on both SERS and elastography (81%) was superior to that yielded by SERS spectra alone (75%) and elastography data alone (71%). This preliminary study is the first report on the use of 2D-SWE of parotid glands for the diagnosis of SjS as well as the first to describe the diagnosis of SjS based on the SERS spectra of dried saliva samples, the results suggesting that the strategy of combining the two methods could improve the diagnosis of SjS.

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.

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.

Does acoustic radiation force elastography improve the diagnostic capability of ultrasound in the preoperative characterization of masses of the parotid gland?

OBJECTIVES:

Ultrasound is the method of choice for preoperative evaluation of tumours of the parotid glands. However, existing methods do not allow for clear differentiation between the most common benign tumours and malignant tumours. The aim of our study was to evaluate if acoustic radiation force, Virtual Touch Quantification (VTQ) elastography helps to improve the preoperative evaluation of parotid masses.

METHODS:

We investigated the parenchyma of 102 parotid glands, 14 lymph nodes of healthy volunteers and 51 tumours of the parotid gland via ultrasound, colour Doppler ultrasound and VTQ. The results were matched with histopathology and analyzed.

RESULTS:

The perfusion in pleomorphic adenoma, the most frequent benign tumour of the parotid gland, was significantly lower in comparison to malignant tumours. All tumours showed statistically significant higher perfusion in comparison to the parenchyma or the lymph nodes of the gland. Shear wave velocity of the user-defined region of interest was statistically significant more frequently an overflow value higher than 8.5 m/s in total tumours in comparison to parenchyma or lymph nodes. The different tumour types presented no significant difference in the shear wave velocity.

CONCLUSIONS:

VTQ in combination with classical ultrasound examination provides additional data useful in distinguishing between benign and malignant tumours and thus shows promise for integration into preexisting ultrasound protocols. However, despite the improvement, clear differentiation of tumours is still not possible and further investigation is recommended.

Shear Wave Elastography Improves Specificity of Ultrasound for Parotid Nodules

OBJECTIVES

This study aimed to determine the performance of Virtual Touch tissue quantification (VTQ) technique in the differential evaluation of parotid gland nodules.

METHODS

Acoustic radiation force impulse VTQ technique was used to determine the shear wave velocity (SWV) of 76 patients with parotid nodules and 30 subjects with normal parotid gland. These nodules were assigned to benign and malignant nodules according to histopathology, measurements of SWV were compared, a cutoff point for benign and malignant nodules was obtained with reference to receiver-operating characteristic curve, and relevant sensitivity and specificity were evaluated.

RESULTS

There were 61 of 76 patients with benign parotid nodules and 15 of 76 patients with malignant nodules. The SWV of the malignant nodules was higher than the SWV of the benign nodules, and the SWV of the benign and malignant nodules was higher than the normal parotid glands. There were significant differences between benign and malignant nodules as well as normal parotid glands in terms of the age and SWV of the nodules (all P < 0.001). The area under the curve is 0.893, the cutoff is 2.445 m/s, and the sensitivity and specificity are 80.0% and 91.8%, respectively.

CONCLUSIONS

Acoustic radiation force impulse VTQ technique can determine the stiffness of parotid nodules in general, its ability to distinct malignant from benign nodular nodule is still not strong, and overlay of SWV of VTQ between benign and malignant nodules is the main impedance to set cutoff point.

Limitations and opportunities of non-invasive liver stiffness measurement in children

Changes in liver structure are an important issue in chronic hepatopathies. Until the end of the 20^th century, these changes could only be determined by histological analyses of a liver specimen obtained via biopsy. The well-known limitations of this technique (i.e., pain, bleeding and the need for sedation) have precluded its routine use in follow-up of patients with liver diseases. However, the introduction of non-invasive technologies, such as ultrasound and magnetic resonance imaging, for measurement of liver stiffness as an indirect marker of fibroses has changed this situation. Today, several non-invasive tools are available to physicians to estimate the degree of liver fibrosis by analysing liver stiffness. This review describes the currently available tools for liver stiffness determination that are applicable to follow-up of liver fibrosis/cirrhosis with established clinical use in children, and discusses their features in comparison to the “historical” tools.

Effect of liposomal local therapy on salivary glands in acoustic radiation force impulse imaging in Sjögren's syndrome

The purpose of this study was to evaluate the utility of acoustic radiation force impulse (ARFI) imaging as a monitoring tool for the effect of a liposomal local therapy in patients with dry mouth symptoms due to primary Sjögren's syndrome (pSS). Fifty patients with pSS, diagnosed according to the American-European Consensus Group (AECG) criteria, were included. Clinical data were collected, and sonographic examination including ARFI imaging of the parotid and submandibular glands was performed. Subjective symptoms were evaluated via visual analogue scales (VAS), and the unstimulated whole salivary flow was measured. After a two-month period of liposomal local therapy, sonographic examination was repeated and both subjective and objective symptoms were re-evaluated. Before local treatment, the mean ARFI value of parotid glands was 2.96 m/s (SD 0.97). Mean ARFI value of the submandibular glands was 2.09 m/s (SD 0.71). After the two-month treatment period, a significant decline of ARFI values in the parotid glands to a value of 2.34 m/s (SD 0.70, p < 0.001) could be observed. The submandibular glands did not show any significant change. Further, a significant reduction of the subjective sensation of dry mouth symptoms could be observed (p = 0.0001). With the application of ARFI imaging, a decline in parotid gland stiffness could be observed in patients with primary Sjögren's Syndrome accompanied by a significant improvement of the subjective sensation of dry mouth symptoms. The seromucous submandibular glands did not show any changes compared to the serous parotid glands.