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

Cancer therapy-related salivary dysfunction

Salivary gland dysfunction is a common side effect of cancer treatments. Salivary function plays key roles in critical daily activities. Consequently, changes in salivary function can profoundly impair quality of life for cancer patients. We discuss salivary gland anatomy and physiology to understand how anticancer therapies such as chemotherapy, bone marrow transplantation, immunotherapy, and radiation therapy impair salivary function. We discuss approaches to quantify xerostomia in the clinic, including the advantages and limitations of validated quality-of-life instruments and approaches to directly measuring salivary function. Current and emerging approaches to treat cancer therapy-induced dry mouth are presented using radiation-induced salivary dysfunction as a model. Limitations of current sialagogues and salivary analogues are presented. Emerging approaches, including cellular and gene therapy and novel pharmacologic approaches, are described.

Clinical and radiographic follow-up after the Wilkie procedure at 28 years: A case report

Rerouting of the parotid ducts posteriorly to drain into the tonsillar fossae (Wilkie procedure) was initially designed to address drooling in patients with cerebral palsy. This procedure was subsequently modified to include bilateral submandibular gland excision and extended to apply to other etiologies of sialorrhea. Our literature review failed to identify report of long-term follow-up beyond 2 decades following this procedure. We describe a 33-year-old female with spastic cerebral palsy who underwent the Wilkie procedure to treat sialorrhea and, 25 years later, developed right-sided facial swelling and dental infections in association with xerostomia. CT imaging showed symmetric atrophy of the parotid glands with fat replacement interspersed with fibrosis. Ultrasound analysis with shear wave elastography offered the additional interpretation of a greater degree of gland stiffness involving the tail of the recently inflamed right parotid gland compared to the left. This case report identifies long-term complications associated with xerostomia following initial success employing the Wilkie procedure to address sialorrhea. The radiographic evaluation supports the contention that rerouting of Stensen's duct may be associated with chronic obstructive changes to the parotid gland. Ultrasound shear wave elastography supplemented CT imaging by identifying asymmetric stiffness of the parotid glands as was consistent with the more recent right parotid inflammation.

Functional Evaluation of Major Salivary Glands Using Viscosity PLUS and 2D Shear-Wave PLUS Elastography Techniques in Healthy Subjects-A Pilot Study

Biological soft tissues are characterized by viscoelastic properties. The propagation of shear waves within tissues is influenced by both elasticity, which is linked to the shear wave speed, and viscosity, which is linked to the shear wave dispersion. This study aimed to functionally assess the parotid glands (PG) and submandibular glands (SMG) in a group of 40 healthy subjects using the novel Viscosity PLUS (Vi.PLUS) and 2D Shear-Wave Elastography PLUS (2D-SWE.PLUS) techniques. The viscosity and stiffness of PG and SMG were measured before and after gustatory stimulation with a sialagogue agent (commercially available lemon juice) using the new SuperSonic MACH 30 ultrasound system equipped with a curvilinear C6-1X transducer. PG presented a mean basal viscosity and elasticity of 2.10 ± 0.19 Pa.s and 11.32 ± 1.91 kPa, respectively, which significantly increased poststimulation to 2.39 ± 0.17 Pa.s (p < 0.001) and 12.58 ± 1.92 kPa (p < 0.001), respectively. SMG did not present statistically increased values of viscosity and elasticity following stimulation (2.31 ± 015 Pa.s vs. 2.37 ± 0.18 Pa.s, p = 0.086, and 10.40 ± 1.64 kPa vs. 10.90 ± 1.98 kPa, p = 0.074, respectively). Vi.PLUS measurements presented a good positive correlation with 2D-SWE.PLUS values for PG and SMG, before and after stimulation. Gender and BMI were not confounding factors for these two parameters. Vi.PLUS represents an innovative non-invasive imaging technique that, together with 2D-SWE.PLUS proves to be useful in functionally assessing the major salivary glands in healthy subjects.

Can Ultrasound in Combination with Virtual Touch Imaging Quantification Predict the Dignity of a Parotid Tumor?

Pre-operative evaluation of a parotid gland tumor is crucial in guiding treatment. This study evaluates the diagnostic performance of B-mode ultrasound in combination with Virtual Touch imaging quantification (VTIQ) in the assessment of parotid lesions. A prospective study of 268 patients with parotid lesions was conducted. Pre-operative ultrasound findings and VTIQ data were compared against histologic results. Ill-defined margins on ultrasound were associated with a significantly higher risk of malignancy (odds ratio [OR] = 1224.0, 95 % confidence interval [CI]: 151.8-9872.7). Faster mean shear waves on VTIQ (OR = 1.81, 95% CI: 1.47-2.23, per 1 m/s increase) and an area with shear wave velocity >6.0 m/s involving >70 % of the lesion (OR = 19.80, 95 % CI: 6.22-63.07) were associated with higher risk of malignancy. Addition of VTIQ to routine pre-operative B-mode ultrasound can provide supplemental information on the dignity of a parotid tumor, allowing for peri-operative procedural optimization.

The current value of quantitative shear wave sonoelastography in parotid gland tumors

Background

The preoperative differentiation between salivary gland tumor entities using computed tomography, magnetic resonance imaging (MRI) and ultrasound (US) is still limited. Biopsies are often regarded as indispensable for properly characterizing these various lesions. The aim of this study was to analyze the value of acoustic radiation force impulse (ARFI) sonoelastography as an US differentiation tool when examining parotid gland (PG) lesions.

Methods

We included 104 patients with PG masses in this study, employing two different US devices using quantitative ARFI-sonoelastography (Siemens Acuson-S3000, n=59; Siemens Acuson-Sequoia, n=45). The ability of sonoelastographic measurements to differentiate between different neoplasms was compared and analyzed for both US machines.

Results

Quantitative shear wave sonoelastography is limited in its ability to reliably differentiate between tumor entities of the PG as a stand-alone parameter. Measurement results were unsystematically distributed and not transferable between the two US devices. A significant differentiation of benign and malignant lesions was not possible with either US machine (S3000: P=0.770, Sequoia: P=0.382). A differentiation between pleomorphic adenomas (PA) and Warthin tumors was only possible with the Acuson S3000 system (P=0.001, Spearman-Rho =0.492, sensitivity 73.9%, specificity 65.0%).

Conclusions

A reliable identification and differentiation of PG tumors as well as clinical treatment decisions cannot be made with the sole use of ARFI-sonoelastography. The results emphasize the device-dependence and high error-proneness of this US technique when examining lesions of the PG.

Shear wave elastography of the submandibular gland in healthy individuals

OBJECTIVES

Shear wave elastography is a rapidly evolving new technique. The purpose of the present study was to determine the sonoelastographic features of the submandibular glands in healthy individuals.

METHODS

We conducted a cross-sectional study of 45 healthy individuals, whose submandibular glands were studied using shear wave elastography. The stiffness of both submandibular glands was measured and its relationships with the age, sex, body mass, body mass index (BMI), and height of the participants were assessed.

RESULTS

The participants had a mean age of 31.82 ± 5.53 years, a mean height of 158.30 ± 7.16 cm, a mean body mass of 57.83 ± 8.84 kg, and a mean BMI of 22.99 ± 2.72 kg/m². The mean shear elastic modulus of the right and left submandibular glands were 18.02 kPa and 19.09 kPa, respectively. Positive correlations were found between the elasticity of the right submandibular gland and the anthropometric parameters.

CONCLUSION

The elastic modulus of the submandibular glands has been determined in healthy individuals and the data generated can serve as a reference for future studies of pathological conditions of these structures.

Multimodal Ultrasound Including Virtual Touch Imaging Quantification for Differentiating Cervical Lymph Nodes

Defining the entity of cervical lymph nodes (LNs) is essential for the diagnosis and staging of head and neck malignancies. Virtual Touch imaging quantification (VTIQ) is a relatively new method of elastography that measures tissue stiffness quantitatively. A prospective study was conducted that included 108 patients (57 benign and 51 metastatic lymph nodes [MLNs]). Shear wave velocities (SWVs) were analyzed using VTIQ and were compared with the histopathological results. Both maximum and minimum SWVs within the LNs significantly differed between benign masses and MLNs (p < 0.001). Percentage areas of the node with SWVs >6 m/s and <3.5 m/s differed significantly (p < 0.001). Intralesional areas with SWVs ≤3.5 m/s of 0-29% (odds ratio: 93.7) and 30%-69% (odds ratio: 46.3) were predictive of malignant LNs as well as ill-defined tumor (odds ratio: 5.2). VTIQ can provide more information on the entity of cervical LNs.

Two-Dimensional Shear Wave Elastography of Normal Soft Tissue Organs in Adult Beagle Dogs; Interobserver Agreement and Sources of Variability

Shear wave elastography (SWE) induces lateral shear wave through acoustic pulses of the transducer and evaluates tissue stiffness quantitatively. This study was performed to evaluate feasibility and reproducibility of two-dimensional shear wave elastography (2D SWE) for evaluation of tissue stiffness and to examine technical factors that affect shear wave speed (SWS) measurements in adult dogs. Nine healthy, 2 year-old, adult beagles with the median weight of 9.8 kg were included. In this prospective, experimental, exploratory study, 2D SWE (Aplio 600) from the liver, spleen, kidneys, pancreas, prostate, lymph nodes (submandibular, retropharyngeal, axillary, medial iliac, and inguinal), submandibular salivary gland, and thyroid was performed in anesthetized beagles. Color map was drawn and SWS of each SWE were measured as Young’s modulus (kPa) and shear wave velocity (m/s). The effect of measuring site, scan approach, depth, and anesthesia on SWE was assessed in abdominal organs by two observers independently. A total of 27 SWE examinations were performed in 12 organs by each observer. All SWS measurements were preformed successfully; however, SWE in the renal medulla could not be successfully conducted, and it was excluded from further analysis. Interobserver agreement of SWE was moderate to excellent in all organs, except for the left liver lobe at 10–15 mm depth with the intercostal scan. In the liver, there was no significant effect of the measuring site and scan approach on SWE. SWS of the liver and spleen tended to be higher with increasing the depth, but no significant difference. However, anesthesia significantly increased tissue stiffness in the spleen compared to awake dog regardless of the depth (P < 0.05). There was a significant difference in SWS according to the measuring site in the kidneys and pancreas (P < 0.001). 2D SWE was feasible and highly reproducible for the estimation of tissue stiffness in dogs. Measuring site and anesthesia are sources of variability affecting SWE in abdominal organs. Therefore, these factors should be considered during SWS measurement in 2D SWE. This study provides basic data for further studies on 2D SWE on pathological conditions that may increase tissue stiffness in dogs.

Stiffness and Anisotropy Effect on Shear Wave Elastography: A Phantom and in Vivo Renal Study

Tissue elasticity is related to the pathologic state of kidneys and can be measured using shear wave elastography (SWE). However, SWE quantification has not been rigorously validated. The aim of this study was to evaluate the accuracy of SWE-measured stiffness and the effect of tissue anisotropy on SWE measurements. Point SWE (pSWE), 2-D SWE and dynamic mechanical analysis (DMA) were used to measure stiffness and evaluate the effect of tissue anisotropy on the measurements. SWE and DMA were performed on phantoms of different gelatin concentrations. In the tissue anisotropy study, SWE and DMA were performed on the outer cortex of sheep kidneys. In the in vivo study, 15 patients with different levels of interstitial fibrosis were recruited for pSWE measurements. Another 10 healthy volunteers were recruited for tissue anisotropy studies. SWE imaging revealed a non-linear increase with gelatin concentration. There was a significant correlation between pSWE and 2-D SWE, leading to the establishment of a linear regression equation between the two SWE ultrasound measurements. In the anisotropy study, the median difference in stiffness between shear waves oriented at 0° and 90° towards the pyramid axis was significant. In the in vivo study, there was a strong positive linear correlation between pSWE and the percentage of interstitial fibrosis. There was a significant difference in the Young's modulus (YM) between severities of fibrosis. The mean YM values were lower in control patients than in patients with mild, moderate and severe fibrosis. YM values were also significantly higher when shear waves were oriented at 0° toward the pyramid axis. Tissue stiffness and anisotropy affects SWE measurements. These factors should be recognized before applying SWE for the interpretation of measured values.

Ultrasonographic and elastographic biometry in adult major salivary glands: a preliminary case-control report

Specifications about the size and stiffness of healthy salivary glands with ultrasound (US) are not available for Asian people. Using a Toshiba Apolio 500 US platform, we determined the size (including anterior-posterior median length, median paramandibular depth dimension, and cranio-caudal height) and hardness of 100 healthy submandibular and parotid glands in volunteers without a history of disease affecting the salivary glands or post-radiation, and compared the dimensions to those of 36 parotid glands and 37 submandibular glands in post-irradiated patients. The dimensions of the parotid and submandibular glands were significantly correlated with body weight. However, the dimension of the parotid glands was not significantly correlated with that of patients with prior radiation; the shear wave velocity (SWV) significantly increased (1.99 m/s versus 2.43 m/s, p-value < 0.01). The dimension of the submandibular glands was significantly correlated with prior radiation, where the SWV also significantly increased (2.32 m/s versus 2.50 m/s, p-values < 0.01). We find that US is a useful tool for assessment of the reference dimensions and hardness of major salivary glands that may be altered by irradiation.

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.

Ultrasound Shear Wave Elastography: Variations of Liver Fibrosis Assessment as a Function of Depth, Force and Distance from Central Axis of the Transducer with a Comparison of Different Systems

We evaluated variation in fibrosis staging caused by depth, pre-load force and measurement off-axis distance on different ultrasound shear wave elastography (SWE) systems prospectively in 20 patients with diffuse liver disease. Shear wave speed (SWS) was measured with transient elastography, acoustic radiation force impulse (ARFI) and 2-D shear wave elastography (SWE). ARFI and 2-D-SWE measurements were obtained at different depths (3, 5 and 7 cm), with different pre-load forces (4, 7 and 10N and variable) and at 0, 2 and 4cm off the central axis of the transducer. A single, blinded pathologist staged fibrosis using the METAVIR system (F0-F4). Area under the receiver operating characteristic curve was charted to differentiate significant fibrosis (F ≥ 2). Depth was the only factor found to influence ARFI-derived values; no acquisition factors were found to affect 2-D-SWE SWS values. ARFI and 2-D-SWE for diagnosis of significant fibrosis at a depth of 7cm along the central axis had good diagnostic performance (areas under the receiver operating characteristic curve: 0.92 and 0.82, respectively), comparable to that of transient elastography. Further investigation of this finding will likely be of interest.

Shear wave elastography of parotid glands in pediatric patients with HIV infection

OBJECTIVES

Parotid gland (PG) involvement is common among the patients with HIV infection. Shear wave elastography (SWE) is a noninvasive method used to measure the tissue stiffness of several organs including PG. The aim of this study was to evaluate the tissue stiffness values of PGs of HIV-infected children via SWE and compare the results with the counterparts of healthy subjects.

MATERIALS AND METHODS

This single-center, prospective study included the PG examinations of 23 pediatric HIV patients and 40 healthy children via grayscale ultrasound and SWE. Independent sample T test and Mann-Whitney U test were used in statistical analysis.

RESULTS

Stiffness of both PGs was significantly higher in patients' group when compared with control subjects. In addition, when the patients were separated into two groups according to the appearance of PG on grayscale ultrasound as homogeneous and heterogeneous, stiffness values were increased in the patients with homogeneous parenchymal appearance. No significant difference was achieved in terms of median CD4 and CD8 counts, HIV RNA levels or median duration of illnesses.

CONCLUSIONS

PG examination of HIV-infected children via SWE reveals increased tissue stiffness when compared with healthy subjects. SWE can be used as an ultrasound-assisted noninvasive technique in this manner.

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.

Evaluation of parotid glands in healthy children and adolescents using shear wave elastography and superb microvascular imaging

OBJECTIVES

We aim to determine parotid gland elasticity values from healthy children and adolescents using shear wave elastography (SWE). We also define the degree of vascularity using superb microvascular imaging (SMI), power Doppler (PD), and color Doppler (CD) and compare SMI with CD and PD.

MATERIALS AND METHODS

A total of 100 cases, comprising 50 girls and 50 boys, with ages ranging from 3 to 17 years were included in this prospective study. SWE, SMI, PD, and CD measurements were taken from both parotid glands, and the relationships with sex, age, and body mass index (BMI) were determined. The SMI was compared with the PD and CD.

RESULTS

The median elasticity values measured with SWE were 8.37 ± 2.09 kPa and 1.68 ± 0.26 m/s on the right and 8.33 ± 2.04 kPa and 1.69 ± 0.26 m/s on the left. There were significant positive correlations present for those aged below and above 10 years and for BMI with elasticity values. The median vascular spot numbers measured using SMI, PD, and CD were 5 ± 1.70, 3.5 ± 1.45, and 2 ± 1.1 on the right and 4 ± 1.7, 4 ± 1.43, and 2 ± 1.05 on the left, respectively. The median values obtained with SMI were significantly higher than the median values obtained with both PD and CD.

CONCLUSION

This study determined the reference SWE, SMI, PD, and CD values for normal parotid glands in healthy children and adolescents. Elasticity values were affected by age and BMI. There was no correlation between vascularity values and age, sex, or BMI. SMI provided more detailed information about vascularity compared with the other methods.

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

Acoustic radiation force impulse (ARFI) imaging enables the sonographic measurement of tissue stiffness. The aim of this study was to evaluate if experience in ARFI imaging influences the reproducibility of ARFI imaging of the head and neck. Three experienced sonographers and three inexperienced sonographers performed ARFI imaging of thyroid, submandibular and parotid glands in 10 healthy volunteers. The examination was repeated after 2 wk. Ten single ARFI measurements were done in every gland. Inter-rater and intra-rater reliability was analyzed using the intra-class correlation coefficient (ICC). Moderate agreement was observed between experienced and inexperienced examiners (ICC = 0.46). In salivary glands, agreement was fair between the groups (ICC = 0.33), whereas in separate evaluations, inter-rater reliability in the submandibular glands was moderate (ICC = 0.52), and that in the parotid glands, only poor (ICC = 0.09). For ARFI imaging of the thyroid gland, there was moderate agreement between the groups (ICC = 0.50). The intra-rater reliability for the salivary and thyroid glands together and separately was strong in both groups. ARFI imaging of the thyroid and salivary glands did exhibit good reproducibility. ARFI imaging of the thyroid gland reached the highest levels of inter- and intra-observer agreement in both groups. ARFI imaging in salivary glands is only reproducible with experienced examiners.

Sonoelastographic Modalities in the Evaluation of Salivary Gland Characteristics in Sjögren's Syndrome

The purpose of this study was to investigate salivary tissue assessment with various sonoelastographic modalities (real-time tissue elastography, Virtual Touch imaging and quantification) in patients with Sjögren's syndrome as compared with an appropriate control group. The sonoelastographic modalities were evaluated in 50 patients with primary Sjögren's syndrome (pSS). Patients underwent high-resolution ultrasonography of the submandibular and parotid glands. Results of B-mode, real-time tissue elastography, Virtual Touch imaging-each graded with the appropriate scoring system-and Virtual Touch quantification were compared with those for 50 patients with sicca symptoms who did not fulfill the American-European consensus group criteria. In B-mode, 34 of 50 parotid glands in patients with pSS and 8 of 50 in the control group had abnormal findings (p < 0.001). Compared with 9 of 50 control patients, 38 of 50 patients with pSS had abnormal findings in submandibular gland B-mode (p < 0.001). With real-time tissue elastography, there was a trend toward higher scores for parotid glands in the pSS group (p = 0.238), whereas scores for submandibular glands in the control group were higher (p = 0.107). Virtual Touch imaging did not indicate any difference (p = 0.647 and p = 0.658). In Virtual Touch quantification, values for parotid (mean: 2.99 m/s) and submandibular glands (mean: 2.54 m/s) in the pSS group were higher than those for parotid (mean: 2.16 m/s) and submandibular (mean: 2.04 m/s) glands in the control group (p < 0.001 and p = 0.008). Glandular stiffness, measured by Virtual Touch quantification, was significantly higher in patients with Sjögreńs syndrome than in patients with sicca symptoms.