Shear-Wave Elastography in the Characterization of Pleural Effusions

Current evidence for lung ultrasound elastography in the field of pneumology: a systematic review

Background and objectives

Elastography is a technology that has strongly impacted several medical specialties; however, it is not yet applied as part of standard clinical practice in the field of pulmonology. The objective of this systematic review is to analyse the evidence available to date in relation to pleuropulmonary ultrasound elastography, focusing on the three pathologies with the most publications: subpleural consolidations, interstitial lung diseases and pleural effusion.

Methods

Original in vivo studies published up until 12 August 2023 in the Embase, MEDLINE or Web of Science databases were included. The QUADAS-2 tool was applied to analyse bias.

Results

We found 613 records in database search. After duplicates removal, we screened 246 records and finally included 18 papers. The average cohort sample size was 109 patients. The elastography modes most frequently used were strain (22.2%), transient elastography (22.2%), point shear-wave elastography (38.9%) and two-dimensional shear-wave elastography (22.2%). The possibility of a meta-analysis was ruled out because of the heterogeneity of the studies included.

Discussion

The currently available literature indicates that pleuropulmonary ultrasound elastography produces promising and consistent results, although the lack of standardisation in the use of the technique and in the elastography modes employed still impedes its use in daily clinical pneumology practice. The development of a clinical guideline establishing a common nomenclature and standardised techniques for pleuropulmonary elastography will be imperative to generate quality scientific evidence in this field.

Comparison of Medical Treatment Efficiency With Shear Wave Elastography Values of Thrombus in Patients With Lower Extremity Deep Vein Thrombosis

ABSTRACT

In lower-extremity deep vein thrombosis (DVT), thrombus age is essential for successful treatment. The aim of our study was to compare the shear wave elastography (SWE) values measured before treatment and achieved lumen patency after treatment in lower-extremity DVT patients with total occlusion. Patients diagnosed with DVT in the acute-subacute stage (<4 week) with total thrombosis in lower extremity were included in this prospective study. Shear wave elastography measurements were performed where the thrombus was most prominent and homogeneous. To evaluate patient response to treatment, lumen patency (partial [>25%] or total recanalization) was examined using color Doppler imaging in the first and third months posttreatment. Shear wave elastography values with and without patency were compared using an independent t test. Among 75 patients in this study, at the first-month color Doppler imaging examination, the SWE values were 1.77 ± 0.49 (1.09-3.03) m/s in patients who achieved lumen patency (n = 42) and 2.21 ± 0.54 (1.24-3.36) m/s in those who did not show lumen patency (n = 33). The difference between the groups' mean elastography value was statistically significant ( P < 0.001). At the third-month examination, the SWE values were 1.76 ± 0.46 (1.09-3.03) m/s in patients with lumen patency (n = 55) and 2.52 ± 0.48 (1.74-3.36) in patients without lumen patency (n = 20). The difference between the 2 groups' mean elastography value was statistically significant ( P < 0.001). We concluded that it is more difficult to achieve lumen patency in veins occluded by thrombus with higher elasto values, and endovascular interventional procedures should be considered during the initial treatment of high SWE value thrombosis.

Does ARFI elastography complement B-mode ultrasonography in the radiological diagnosis of idiopathic granulomatous mastitis and invasive ductal carcinoma?

BACKGROUND

Idiopathic granulomatous mastitis (IGM) is a chronic, unpleasant autoimmune inflammatory condition and is clinically and radiologically often confused with breast malignancy.

PURPOSE

To investigate the contributions of qualitative and quantitative aspects of acoustic radiation force impulse (ARFI) elastography to the differential diagnosis between IGM and invasive ductal carcinoma (IDC) in the breast.

MATERIAL AND METHODS

Ninety-four women with IDC and 39 with IGM were included in the study. Shear wave velocity (SWV) was calculated for all lesions using quantitative elastography. Next, each lesion's correspondence on qualitative elastographic images to those on the B-mode images was evaluated: pattern 1, no findings on elastography images; pattern 2, lesions that were bright inside; pattern 3, lesions that contained both bright and dark areas; and pattern 4, lesions that were dark inside. Pattern 4 was subdivided into 4a (dark area same size as lesion) and 4b (dark area larger than lesion size). Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy were calculated.

RESULTS

The mean SWV based on ARFI elastography was 3.78 ± 1.26 m/s for IGM and 5.34 ± 1.43 m/s for IDC lesions (P < 0.05). Based on qualitative ARFI elastography, IDC lesions were mostly classified as pattern 4b, while IGM lesions were mostly classified as pattern 1 or 2 (P = 0.01). Evaluation of both the qualitative and quantitative aspects of ARFI elastography yielded a sensitivity of 89% and specificity of 84%.

CONCLUSION

ARFI elastography may facilitate the differential diagnosis between IGM and IDC.

Application of Transthoracic Shear Wave Elastography in Evaluating Subpleural Pulmonary Lesions

AIM

The objective of this research was to investigate the feasibility of transthoracic shear wave elastography in the differentiation of subpleural masses.

METHODS

Between December 2019 and November 2020,82 consecutive patients with radiographic evidence (including chest X ray and thoracic computed tomography CT) of single subpleural lesion enrolled in this research. The Young's modulus E (including E_mean and E_max) of each lesion was detected, and the Young's modulus E of malignant lesions were compared with those of benign ones. We made diagnoses according to the results of pathology or standard clinical course for at least 3 months. Receiver operating characteristic (ROC) analysis was plotted to determine the cut-off point by maximizing the Youden index.

RESULTS

The E_mean and E_max of the benign and malignant group was 34.68 ± 12.12 kPa vs. 53.82 ± 11.95 kPa (p < 0.001), 57.77 ± 14.45 kPa vs. 76.62 ± 17.04 kPa (p < 0.001). The ROC of E_mean showed that when the cut-off point was 43.8 kPa, the Youden index (0.53) for distinguishing benign and malignant tumors was the largest (sensitivity 80.4 %, specificity 72.2 %, AUC = 0.848, p < 0.0001). When the cut-off point recommended by E_max ROC was 73.5 kPa, the Youden index (0.44) for distinguishing benign and malignant tumors was the largest (sensitivity 76.1 %, specificity 66.7 %, AUC = 0.780, p < 0.0001).

CONCLUSIONS

This study demonstrated that we can employ transthoracic shear wave elastography as a valuable instrument in differentiating benign subpleural lesions from malign ones.

Spleen Stiffness Measurement by Using Shear-Wave Elastography as a Predictor of Progression to Secondary Myelofibrosis

OBJECTIVE

Polycythemia vera (PV) and essential thrombocythemia (ET) are chronic myeloproliferative diseases that can transform to secondary myelofibrosis (SMF). In this study, we evaluated spleen stiffness using shear-wave elastography (SWE) as a predictor of progression to SMF.

METHODS

Participants were grouped as healthy volunteers (HVs), PV/ET patients, and SMF patients. Participants' spleen sizes, spleen stiffness values, bone marrow fibrosis degrees, and the other parameters were evaluated. Spleen stiffness values and spleen sizes were compared between groups.

RESULTS

Of the 121 participants included in this study, 52 patients were HVs, 52 patients were PV and/or ET patients, and 17 patients were SMF patients. In terms of age and sex, there was no difference between groups. Splenic parenchymal stiffness median values by using SWE were found to be 0.82 m/s in HVs, 1.41 m/s in PV/ET patients, and 2.32 m/s in SMF patients (P < 0.001). In terms of median length of the spleen, the difference between groups was significant (P < 0.001). In addition, we found a significant positive correlation between spleen stiffness and bone marrow fibrosis degree (P < 0.001, r = 0.757). However, in multivariate analysis, there was no strong independent risk factor for spleen stiffness.

CONCLUSION

In this study, we showed that measurement of spleen stiffness using SWE can distinguish SMF from PV/ET patients and HVs. Therefore, we believe that SWE may be used as a noninvasive and easily accessible method to check the fibrotic progression of bone marrow in PV and ET patients to monitor the transformation to SMF, and enables to detect fibrosis in early phase.

Efficacy of Shear Wave Elastography in the Differentiation of Acute and Subacute Deep Venous Thrombosis

ABSTRACT

It is important to know the age of clot formation to determine an appropriate treatment for deep vein thrombosis (DVT). The present study aims to differentiate between acute and subacute DVT using the shear wave elastography (SWE) technique. Patients with complaints no longer than 4 weeks and who were found to have early-stage (acute-subacute) thrombus on ultrasound (US) between January 2020 and May 2020 were included in the study. All of the patients underwent SWE using a Philips Healthcare EPIQ 5 Ultrasound System Inc. device with a high-resolution linear US probe (eL18-4, 22-2 MHz). Included in the study were 50 patients, including 23 with acute DVT and 27 with subacute DVT. Of the patients, 22 were women and 28 were men, and the mean age was 46.32 ± 11.33 years (range: 24-74 years). The mean SWE value was 2.63± 0.16 (2.39-2.96) in patients with acute DVT and 3.34± 0.31 (2.65-3.88) in patients with subacute DVT. The findings were statistically significant in the comparison of the 2 groups using an independent samples t test (P < 0.001). In the receiver operating characteristic analysis, the area under the curve was found to be 97.6%. When the cutoff value was taken as 2.85 according to the area under the curve, sensitivity was found to be 96.3%, and specificity was 91.3%. Thrombus stage plays a critical role in treatment decisions in DVT in the lower extremities. The present study reveals that the shear wave US elastography technique can be used to discriminate between acute and subacute DVT.

Ultrasound Elastography in the Differentiation of Simple Cyst and Type I Hydatid Cyst of the Liver

ABSTRACT

Hydatid cyst (HC) is a parasitic disease that is endemic particularly to the sheep-breeding regions of the world, our country included. Given their propensity to materialize most commonly in the liver, our study evaluates the value of ultrasound elastography in the differential diagnosis of simple cyst and type I HCs of the liver.The study involved a total of 73 cysts (22 simple cysts, 51 type I HCs) that were removed using the puncture aspiration injection reaspiration technique between 2016 and 2018. All measurements were made using a Siemens ACUSON S2000 (Siemens Healthcare, Erlangen, Germany) device with a 4-MHZ 4C1 convex probe, an acoustic radiation force impulse elastography procedure, and a Virtual Touch IQ option. The difference between the mean shearwave elastography (SWE) values of both groups was analyzed with an independent t test.Of the 70 patients involved in the study, 29 were female and 41 were male, with a mean ± SD age of 38.85 ± 17.62 years (range, 5-82 years). Upon the examination of the 22 simple cysts and the 51 HCs, the mean ± SD SWE values were found to be 2.6 ± 0.96 (0.96-4.25) and 2.8 ± 1.69 (0.66-4.84), respectively. No statistically significant difference was identified between the SWE values of type I HCs and simple cysts (P > 0.005).Although HCs and simple cysts had similar radiological appearances, and a relative difference was noted in the differentiation of the elastographic measurements, this difference was not statistically significant. Accordingly, more comprehensive and various studies are needed.

Application of transthoracic shear-wave ultrasound elastography in lung lesions

INTRODUCTION

Tissue stiffness information may help in the diagnosis of lung lesions. This study aimed to investigate and validate the application of transthoracic two-dimensional shear-wave ultrasound elastography in differentiating malignant from benign subpleural lung lesions.

METHODS

This study involved one retrospective observational derivation cohort from January 2016 to December 2017 and one prospective observational validation cohort from December 2017 to December 2019. The inclusion criterion was radiographic evidence of pulmonary lesions. The patients were categorised into air bronchogram and hypoechoic groups based on B-mode grayscale images. The elasticity of subpleural lung lesions with acceptable shear-wave propagation was measured. Diagnoses were made on the basis of pathology, microbiological studies or following up the clinical course for at least 6 months.

RESULTS

A total of 354 patients were included. Among the 121 patients in the derivation cohort, a receiver operating characteristic curve was constructed and the cut-off point to differentiate benign from malignant lesions was 65 kPa with a Youden index of 0.60 and an accuracy of 84.3%. Among the 233 patients in the validation cohort, the diagnostic performance was maintained, with a Youden index of 0.65 and an accuracy of 86.7%. Upon applying the cut-off point to the air bronchogram group, the Youden index was 0.70 and the accuracy was 85.0%.

CONCLUSIONS

This study validated the application of transthoracic shear-wave ultrasound elastography for assessing lung malignancy. A cut-off point of 65 kPa is suggested for predicting lung malignancy. Furthermore, for pulmonary air bronchogram lesions with high elasticity, tissue proofing should be considered because of the high possibility of malignancy.

Comparison of Efficiencies Between Shear Wave Elastography, Fine-Needle Aspiration Biopsy and American College of Radiology Thyroid Imaging Reporting and Data System Scoring System in Determining the Malignity Potential of Solid Thyroid Nodules

ABSTRACT

We aimed to evaluate the efficiencies of quantitative shear-wave elastography, fine-needle aspiration (FNA) biopsy and American College of Radiology (ACR)-thyroid imaging reporting and data system (TIRADS) scoring system in determining the malignity potential of solid thyroid nodules. In period between September 2014 and January 2016, 191 solid thyroid nodules of 189 patients were enrolled in this study. The mean shear wave velocities of the nodules were recorded by acoustic radiation force impulse method. All nodules were classified according to ACR-TIRADS scoring system and underwent FNA procedure. The cytopathologic results (after FNA) were benign in nature, atypical-cytology/suspiciously malign and highly suspicious of malignity in 117, 28, and 21 nodules, respectively. The specimen from FNA was insufficient in 25 nodules. Thirty-four nodules of 33 enrolled patients were operated, and the efficiencies of shear wave elastography, FNA, and ACR-TIRADS procedures were statistically analyzed; relying on the histopathologic results, the shear-wave elastography had 83.3% sensitivity, 93.7% specificity (with a cutoff value of 2,74 m/s), the FNA had 94.4% sensitivity, 87.5% specificity, and ACR-TIRADS had 88.2% sensitivity, 94.1 specificity in determining malignant tyroid nodules (P < 0.005). Quantitative shear wave elastography is concluded to be an effective, noninvasive, and practical imaging modality with a lesser sensitivity and specificity values than TIRADS unless a lower sensitivity but a higher specificity values than FNA (93.7% vs 87.5%) in considering the malignity potential of solid thyroid nodules.