Endoscopic ultrasound, endoscopic sonoelastography, and strain ratio evaluation of lymph nodes with histology as gold standard

Associations of Real-Time Ultrasound and Strain and Shear Wave Elastography with Gastrointestinal Organs: A Systematic Review

Ultrasound elastography is gaining attention for its diagnostic potential across various medical fields, and its physical properties make it valuable in modern clinical medicine. However, its specific attributes, especially in the context of recent medical advancements, remain relatively unexplored. This study aimed to identify instrument-specific characteristics and applications of real-time ultrasound elastography, shear wave elastography, and strain elastography, particularly within gastroenterology. Following PRISMA guidelines, the study examined elastography articles on databases like PubMed, resulting in 78 included articles. Data on patient demographics, organ involvement, specificity, sensitivity, accuracy, positive predictive value, and negative predictive value were extracted. Statistical analysis involved SPSS version 21, with significance set at p < 0.05. The majority of patients were male (50.50%), with a mean age of 42.73 ± 4.41 years. Shear wave elastography was the most prevalent technique (48.7%), and liver investigations were predominant in gastroenterology (34.6%). Gastrointestinal applications showed higher sensitivity, positive predictive value, and negative predictive values (p < 0.05) but lower specificity (p < 0.05). Real-time ultrasound elastography exhibited increased specificity, accuracy, and predictive values (p < 0.05). Ultrasound elastography appears more accurate and effective in gastroenterological settings. Nonetheless, its performance depends on instrument-specific and operator-dependent factors. While promising, further studies are necessary to ascertain optimal utilization in both gastrointestinal and non-gastrointestinal conditions.

Endoscopic Ultrasound (EUS) Guided Elastography

Endoscopic ultrasound (EUS) is an essential technique for the management of several diseases. Over the years, new technologies have been developed to improve and overcome certain limitations related to EUS-guided tissue acquisition. Among these new methods, EUS-guided elastography, which is a real-time method for the evaluation of tissue stiffness, has arisen as one of the most widely recognized and available. At present, there are available two different systems to perform an elastographic evaluation: strain elastography and shear wave elastography. Strain elastography is based on the knowledge that certain diseases lead to a change in tissue hardness while shear wave elastography monitored shear-wave propagation and measures its velocity. EUS-guided elastography has shown in several studies high accuracy in differentiating benign from malignant lesions from many different locations, mostly in the pancreas and lymph nodes. Therefore, nowadays, there are well-established indications for this technology, mainly for supporting the management of pancreatic diseases (diagnosis of chronic pancreatitis and differential diagnosis of solid pancreatic tumors) and characterization of different diseases. However, there are more data on new potential indications for the near future. In this review, we will present the theoretical bases of this technology and we will discuss the scientific evidence to support its use.

Ultrasound Elastography to Differentiate the Thrombus and Plaque in Peripheral Arterial Diseases

Purpose

Arterial stiffness and steno-occlusion of the lower-extremity can result from many vascular lesions, including acute thromboembolisms, soft plaques, calcified plaques, or inflammatory disease. Ultrasound (US) elastography measures the tissue deformation response to compression and displays tissue stiffness. This study aimed to evaluate the characteristics of arterial lesions in the lower extremities using US elastography.

Materials and Methods

We retrospectively analyzed the data of 20 patients who visited our institute for arterial disease treatment between May 2016 and November 2017. An US examination with B-mode and strain elastography (SE) was performed of four different lesion types at 45 sites: acute and subacute thromboembolisms, soft plaques, calcified plaques, and thromboangiitis obliterans lesions (TAOs). During SE, stress was externally applied by the operator using the transducer. Strain ratio (SR) was calculated as the fraction of the average strain in the reference area divided by the average strain in the lesion. The SR was compared among different lesion types, with the accompanying vein as the reference region of interest.

Results

The strain was highest in the soft plaques (0.63%±0.23%), followed by the TAOs (0.45%±0.11%), calcified plaques (0.44%±0.13%), and acute thromboembolisms (0.34%±0.23%), which were statistically significant (P=0.026). However, the mean SR was highest for the calcified plaques (2.33%±0.80%), followed by the TAOs (1.63%±0.40%), acute thromboembolisms (1.60%±0.48%), and soft plaques (1.51±0.39), and which were statistically significant (P=0.013).

Conclusion

Despite several limitations, vascular elastography may be useful for differentiating between lesion types in peripheral arterial disease.

The expanding role of endoscopic ultrasound elastography

Endoscopic ultrasound (EUS) is an invaluable tool for assessing various GI diseases. However, using just the conventional B-mode EUS imaging may not be sufficient to accurately delineate the lesion's character. Using the principle of stress-induced tissue strain, EUS elastography (EUS-E) can help in the real-time sonographic assessment of the level of tissue stiffness or hardness of any organ of interest during a routine EUS procedure. Thus, EUS-E can better characterize the lesion's nature and highlight the more suspicious areas within an individual lesion. The most commonly studied lesions with EUS-E are the pancreatic lesions, namely, chronic pancreatitis, pancreatic cancer, and lymph nodes. However, EUS-E is gradually expanding its use for lesion characterization of the liver, bile duct, adrenals, gastrointestinal tract, and even therapy response. Moreover, the use of EUS-E along with other image enhancement techniques such as harmonic EUS and contrast-enhanced EUS can improve the accuracy of the diagnosis. However, several technical aspects need to be standardized before EUS-E can be truly used as a tool for "virtual biopsy". This review focuses on the various technical aspects of the use of EUS-E, it is established and expanding indications and an extensive outline of the various studies on EUS-E. We also discuss the current pitfalls and future trends in EUS-E.

Enhanced EUS imaging (with videos)

BACKGROUND AND AIMS

EUS remains a primary diagnostic tool for the evaluation of pancreaticobiliary disease. Although EUS combined with FNA or biopsy sampling is highly sensitive for the diagnosis of neoplasia within the pancreaticobiliary tract, limitations exist in specific clinical settings such as chronic pancreatitis. Enhanced EUS imaging technologies aim to aid in the detection and diagnosis of lesions that are commonly evaluated with EUS.

METHODS

We reviewed technologies and methods for enhanced imaging during EUS and applications of these methods. Available data regarding efficacy, safety, and financial considerations are summarized.

RESULTS

Enhanced EUS imaging methods include elastography and contrast-enhanced EUS (CE-EUS). Both technologies have been best studied in the setting of pancreatic mass lesions. Robust data indicate that neither technology has adequate specificity to serve as a stand-alone test for pancreatic malignancy. However, there may be a role for improving the targeting of sampling and in the evaluation of peritumoral lymph nodes, inflammatory pancreatic masses, and masses with nondiagnostic FNA or fine-needle biopsy sampling. Further, novel applications of these technologies have been reported in the evaluation of liver fibrosis, pancreatic cysts, and angiogenesis within neoplastic lesions.

CONCLUSIONS

Elastography and CE-EUS may improve the real-time evaluation of intra- and extraluminal lesions as an adjunct to standard B-mode and Doppler imaging. They are not a replacement for EUS-guided tissue sampling but provide adjunctive diagnostic information in specific clinical situations. The optimal clinical use of these technologies continues to be a focus of ongoing research.

Preoperative EUS evaluation of the response to neoadjuvant therapy for gastric and esophagogastric junction cancer is correlated with survival: A single retrospective study of 97 patients

Background and Objectives:

The European Society for Medical Oncology suggests performing EUS staging for esophagogastric junction and gastric cancers to further assess the T and N stages. The use of EUS after neoadjuvant therapy (NT) is still under debate. We aimed to evaluate the contribution of EUS after NT to staging, therapeutic choices, and prognosis prediction.

Subjects and Methods:

In 97 patients with esophagogastric junction and gastric cancers who received NT (chemotherapy or radiochemotherapy) followed by carcinologic surgery, EUS was performed before (uT, uN) and after (yuT, yuN) NT. We compared the results of EUS staging after NT (yuT and yuN) and final histology (ypT and ypN). We analyzed the correlation between overall survival (OS), disease-free survival (DFS), and the objective and subjective responses to NT evaluated by EUS (comparison of uT and yuT and uN and yuN with OS and DFS).

Results:

EUS staging detected metastasis that went undetected by computed tomography in 16% of metastatic patients. The accuracy between EUS after NT and postoperative pathological findings was 44.4% (34.2%; 54.7%) for T stage and 49.3% (37.5%; 61.1%) for N stage. On multivariate analysis, OS had significantly correlated with the objective response to NT. In the case of a response to NT, the median OS was 64.77 months, and in the case of stable disease, the median OS was 22.9 months (P = 0.01).

Conclusion:

EUS after NT can be used for staging. Despite its moderate accuracy, the evaluation of the response to NT by EUS seems to be correlated with patient prognosis.

Slow-pull technique yields better quality smears: prospective comparison of slow-pull and standard suction techniques of endoscopic ultrasound-guided fine-needle aspiration

BACKGROUND

Diagnostic accuracy and quality of smears obtained by endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) are influenced by characteristics of suction and examined organ.

AIMS AND METHODS

Efficiency of EUS-FNA and quality of smears obtained by slow-pull (SP) and standard suction (SS) techniques was prospectively compared in the sampling of pancreatic (N = 56) and extrapancreatic (N = 145) tumors.

RESULTS

SS technique resulted in a higher number of smear pairs both in pancreatic (1.74 vs. 3.19; p < 0.001) and extrapancreatic tumors (1.62 vs. 3.28; p < 0.001); however, it decreased the proportion of diagnostic smears (46.69% vs. 36.52%; p = 0.002 and 49.17% vs. 30.67%; p < 0.001) and increased the bloodiness (1.51 vs. 2.07; p < 0.001 and 1.48 vs. 2.05; p < 0.001). In pancreatic cancers, no difference was observed in terms of diagnostic accuracy (81.38% vs. 83.45%) and cellularity (1.44 vs. 1.27; p = 0.067); however, they were substantially higher in extrapancreatic tumors using SP technique (71.41% vs. 60.71% and 1.34 vs. 0.77; p < 0.001). Only SP technique resulted in a significant difference between examiners in terms of technical success rate and quality of smears without any decrease of diagnostic accuracy.

CONCLUSIONS

SP technique yields better quality smears independently from tumors characteristics; however, it shows significant examiner-dependency. SS technique reduces the diagnostic accuracy of sampling in extrapancreatic tumors.

Experimental model standardizing polyvinyl alcohol hydrogel to simulate endoscopic ultrasound and endoscopic ultrasound-elastography

BACKGROUND

Endoscopic ultrasound (EUS) and endoscopic ultrasound elastography (EUS-E) simulation lessens the learning curve; however, models lack realism, diminishing competitiveness.

AIM

To standardize the mechanical properties of polyvinyl alcohol (PVA) hydrogel for simulating organs and digestive lesions.

METHODS

PVA hydrogel (Sigma Aldrich, degree of hydrolysis 99%) for simulating EUS/EUS-E lesions was investigated in Unidad de Investigación y Desarrollo Tecnológico at Hospital General de México “Dr. Eduardo Liceaga”, Mexico City. We evaluated physical, contrast, elasticity and deformation coefficient characteristics in lesions, applying Kappa’s concordance and satisfaction questionnaire (Likert 4-points).

RESULTS

PVA hydrogel showed stable mechanical properties. Density depended on molecular weight (MW) and concentration (C). PVA bblocks with the greatest density showed lowest tensile strength (r = -0.8, P = 0.01). Lesions were EUS-graphically visible. Homogeneous and heterogeneous examples were created from PVA blocks or PVA phantoms, exceeding (MW₂ = 146000-186000, C₉ = 15% and C₁₀ = 20%) with a density under (MW₁ = 85000-124000, C₁ = 7% and C₂ = 9%). We calculated elasticity and deformation parameters of solid (blue) areas, contrasting with the norm (Kappa = 0.8; high degree of satisfaction).

CONCLUSION

PVA hydrogels were appropriate for simulating organs and digestive lesions using EUS/EUS-E, facilitating practice and reducing risk. Repetition amplified skills, while reducing the learning curve.

Diagnostic Endoscopic Ultrasound: Technique, Current Status and Future Directions

Endoscopic ultrasound (EUS) is now well established as an important tool in clinical practice. From purely diagnostic imaging, it has progressed to include tissue acquisition, which provided the basis for therapeutic procedures. Even as interventional EUS developed, there has been ongoing progress in EUS diagnostic capabilities due to improved imaging systems, better needles for tissue acquisition and development of enhanced imaging functions such as contrast harmonic EUS (CHEUS) and EUS elastography. EUS is well established for differentiation of subepithelial lesions, for T-staging of luminal gastrointestinal and pancreaticobiliary malignancies, for differentiation of benign pancreaticobiliary disorders and for diagnostic tissue acquisition, which can be achieved by EUS-guided fine needle aspiration or by EUS-guided fine needle biopsy using dedicated biopsy needles. This review briefly describes the technique of performing EUS and then discusses its clinical utility in terms of gastrointestinal cancer staging, the evaluation of pancreaticobiliary disorders and tissue acquisition. Enhanced imaging techniques such as CHEUS and EUS elastography are briefly reviewed.

Endoscopic Ultrasound Elastography for Evaluation of Lymph Nodes: A Single Center Experience

Background and Aim

The differentiation between malignant and benign lymph nodes (LNs) is important for tumor staging, for detection of prognosis, and for selection of the best treatment strategy in many cancers. On B-mode EUS, there are some known criteria that suggest the malignant nature of LNs; these criteria may be found in benign LNs. The aim of the work is to evaluate the effectiveness of elasticity score and SR to differentiate between benign and malignant LNs.

Patients and Methods

The study was designed as a retrospective study that included 40 patients with abdominal or mediastinal LNs, either associated with primary masses or isolated, referred for EUS evaluation. Elasticity scores and SR were determined during the examination and finally, EUS-FNA was done at the end of the procedure.

Results

In this 2-years study, 40 patients were enrolled (24 malignant; 16 benign). There were 23 males and 17 females. Their mean age was 52.5 years (range: 28-77). ES alone had a specificity of 87.5%, sensitivity of 41.7%, PPV of 83.3%, NPV of 50%, and accuracy of 60%. Based on the ROC curve analysis results, the best cut-off level of SR to obtain the maximum area under the curve (AUC) was 6.7 with a specificity of 99.9%, sensitivity of 57.1%, PPV of 99.9%, NPV of 64%, and accuracy of 77.5%.

Conclusion

The use of elasticity score and SR increases the reliability of differentiation between benign and malignant LNs and can decrease the number of unnecessary biopsies.

Present status and perspectives of endosonography 2017 in gastroenterology

Endoscopic ultrasound has become an essential tool in modern gastroenterology and abdominal surgery. Compared with all other endoscopic methods, it has the most potential for innovation and its future looks bright. Thus, we compiled this summary of established and novel applications of endoscopic ultrasound methods to inform the reader about what is already possible and where future developments will lead in improving patient care further. This review is structured in four parts. The first section reports on developments in diagnostic endoscopic ultrasound, the second looks at semi-invasive endoscopic ultrasound, and the third discusses advances in therapeutic endoscopic ultrasound. An overview on the future prospects of endoscopic ultrasound methods concludes this article.

Future Directions for Endoscopic Ultrasound: Where Are We Heading?

Endoscopic ultrasound (EUS) plays an important role as a diagnostic and therapeutic modality in gastroenterology. New developments have emerged, especially in the last decade, and are being introduced to endoscopists. The ability to readily visualize and access organs in the gastrointestinal tract has allowed endoscopists to perform new interventional procedures. EUS procedures have taken the place of conventional approaches for the treatment of various gastrointestinal diseases, including pancreatic cystic lesions. This article focuses on the advances and future of diagnostic and therapeutic EUS.

New Imaging Techniques: Endoscopic Ultrasound-Guided Elastography

Endoscopic ultrasound (EUS) is a major imaging method in the management of several diseases of the gastrointestinal tract and surrounding structures. Elastography is a novel technique providing additional information to standard B-mode imaging on the tissue stiffness. Elastography can be performed under EUS guidance. This method has proven to be an accurate and additional tool in the evaluation of pancreatic diseases and lymph nodes analysis. Possible uses include the study of liver lesions, subepithelial masses, and many more. This article reviews current knowledge and future perspectives.

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.

Maximizing the endosonography: The role of contrast harmonics, elastography and confocal endomicroscopy

New technologies in endoscopic ultrasound (EUS) evaluation have been developed because of the need to improve the EUS and EUS-fine needle aspiration (EUS-FNA) diagnostic rate. This paper reviews the principle, indications, main literature results, limitations and future expectations for each of the methods presented. Contrast-enhanced harmonic EUS uses a low mechanical index and highlights slow-flow vascularization. This technique is useful for differentiating solid and cystic pancreatic lesions and assessing biliary neoplasms, submucosal neoplasms and lymph nodes. It is also useful for the discrimination of pancreatic masses based on their qualitative patterns; however, the quantitative assessment needs to be improved. The detection of small solid lesions is better, and the EUS-FNA guidance needs further research. The differentiation of cystic lesions of the pancreas and the identification of the associated malignancy features represent the main indications. Elastography is used to assess tissue hardness based on the measurement of elasticity. Despite its low negative predictive value, elastography might rule out the diagnosis of malignancy for pancreatic masses. Needle confocal laser endomicroscopy offers useful information about cystic lesions of the pancreas and is still under evaluation for use with solid pancreatic lesions of lymph nodes.

Impact of EUS-FNA for preoperative para-aortic lymph node staging in patients with pancreatobiliary cancer

BACKGROUND AND AIMS

In patients with pancreatobiliary cancer, para-aortic lymph node (PALN) metastasis is considered to be the involvement beyond the regional lymph nodes, namely, distant metastasis. Effective methods for preoperative PALN staging, however, are not established. This study aimed to compare the diagnostic capability for PALN metastasis between EUS-FNA and (18)F-fluorodeoxyglucose positron emission tomography with CT (PET/CT).

METHODS

We performed a prospective, nonrandomized, single-center trial. Between December 2010 and March 2014, 208 patients with pancreatobiliary cancer without apparent distant metastasis except for PALNs were assessed for study eligibility before surgery. Among them, 52 consecutive patients with PALN enlargement were enrolled in the study. (18)F-Fluorodeoxyglucose PET/CT and EUS-FNA were performed sequentially as a single combined procedure to evaluate PALN metastases. The primary outcome was to compare the diagnostic capability of EUS-FNA and PET/CT for PALN metastasis.

RESULTS

Of 71 enlarged PALNs in the 52 patients, 30 (42.3%) were finally diagnosed as metastases in 21 patients (40.4%). Of the 21 patients with PALN metastases, preoperative EUS-FNA or PET/CT made a correct diagnosis in 20 (95.2%) or 12 (57.1%), respectively. EUS-FNA had higher sensitivity and specificity for the diagnosis of PALN metastasis (sensitivity, 96.7% [29/30]; 95% confidence interval, 82.2%-99.9%; specificity, 100% [39/39]; 95% confidence interval, 91.0%-100%) than PET/CT.

CONCLUSIONS

EUS-FNA is superior to PET/CT for preoperative PALN staging in patients with pancreatobiliary cancer. Because of the clinical benefit of EUS-FNA to reduce unnecessary surgery, it should be part of the standard preoperative examination for patients with pancreatobiliary cancer. (UMIN clinical trials registry number: 000006408.).

Endoscopic ultrasound elastography: Current status and future perspectives

Elastography is a new ultrasound modality that provides images and measurements related to tissue stiffness. Endoscopic ultrasound (EUS) has played an important role in the diagnosis and management of numerous abdominal and mediastinal diseases. Elastography by means of EUS examination can assess the elasticity of tumors in the proximity of the digestive tract that are hard to reach with conventional transcutaneous ultrasound probes, such as pancreatic masses and mediastinal or abdominal lymph nodes, thus improving the diagnostic yield of the procedure. Results from previous studies have promised benefits for EUS elastography in the differential diagnosis of lymph nodes, as well as for assessing masses with pancreatic or gastrointestinal (GI) tract locations. It is important to mention that EUS elastography is not considered a modality that can replace biopsy. However, it may be a useful adjunct, improving the accuracy of EUS-fine needle aspiration biopsy (EUS-FNAB) by selecting the most suspicious area to be targeted. Even more, it may be useful for guiding further clinical management when EUS-FNAB is negative or inconclusive. In the present paper we will discuss the current knowledge of EUS elastography, including the technical aspects, along with its applications in the differential diagnosis between benign and malignant solid pancreatic masses and lymph nodes, as well as its aid in the differentiation between normal pancreatic tissues and chronic pancreatitis. Moreover, the emergent indication and future perspectives are summarized, such as the benefit of EUS elastography in EUS-guided fine needle aspiration biopsy, and its uses for characterization of lesions in liver, biliary tract, adrenal glands and GI tract.

Endobronchial ultrasound elastography strain ratio for mediastinal lymph node diagnosis

Background

Ultrasound elastography is an imaging procedure that can assess the biomechanical characteristics of different tissues. The aim of this study was to define the diagnostic value of the endobronchial ultrasound (EBUS) elastography strain ratio of mediastinal lymph nodes in patients with a suspicion of lung cancer. The diagnostic values of the strain ratios were compared with the EBUS brightness mode (B-mode) features of selected mediastinal lymph nodes and with their cytological diagnoses.

Patients and methods

This prospective, single-centre study enrolled patients with an indication for biopsy and mediastinal staging after a non-invasive diagnostic workup of a lung tumour. EBUS with standard B-mode evaluation and elastography with strain ratio measurement were performed before endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA).

Results

Thirty-three patients with 80 suspicious mediastinal lymph nodes were included. Malignant infiltration was confirmed in 34 (42.5%) lymph nodes. The area under the receiver operating characteristic curve for the strain ratio was 0.87 (p < 0.0001). At a strain ratio ≥ 8, the accuracy for malignancy prediction was 86.25% (sensitivity 88.24%, specificity 84.78%, positive predictive value [PPV] 81.08%, negative predictive value [NPV] 90.70%). The strain ratio is more accurate than conventional B-mode EBUS modalities for differentiating between malignant and benign lymph nodes.

Conclusions

EBUS-guided elastography with strain ratio assessment can distinguish malignant from benign mediastinal lymph nodes with greater accuracy than conventional EBUS modalities. This new method may reduce the number of mediastinal EBUS-TBNAs and thus reduce the invasiveness and expense of mediastinal staging in patients with non-small lung cancer (NSCLC).

Transcutaneous Ultrasound: Elastographic Lymph Node Evaluation. Current Clinical Applications and Literature Review

Distinguishing malignant versus benign lymphadenopathies is a major diagnostic dilemma in clinical medicine. Metastatic deposits in normal-sized lymph nodes (LNs) can be smaller than a millimeter, thus presenting a diagnostic challenge. In most clinical settings, however, enlarged LNs detected on imaging need to be classified as malignant or benign. Ultrasound seems to be a very reliable method for LN characterization because of the high resolution, especially in the subcutaneous areas. However, B-mode and Doppler-ultrasound criteria for characterization of a lymphadenopathy as benign or malignant are lacking specificity. Newer methods such as elastography seem to be valuable for identifying metastatic deposits within LNs and may help discriminate malignant and benign LNs. This review summarizes the different elastographic methods available and provides an overview of the relevant publications. According to the literature, elastography can be used for identifying metastatic deposits, to guide fine needle aspiration and to non-invasively choose the most suspicious LN of a group of enlarged LNs for targeted biopsy.

Endoscopic ultrasound: Elastographic lymph node evaluation

Different imaging techniques can bring different information which will contribute to the final diagnosis and further management of the patients. Even from the time of Hippocrates, palpation has been used in order to detect and characterize a body mass. The so-called virtual palpation has now become a reality due to elastography, which is a recently developed technique. Elastography has already been proving its added value as a complementary imaging method, helpful to better characterize and differentiate between benign and malignant masses. The current applications of elastography in lymph nodes (LNs) assessment by endoscopic ultrasonography will be further discussed in this paper, with a review of the literature and future perspectives.

New endoscopic ultrasound techniques for digestive tract diseases: A comprehensive review

Endoscopic ultrasound (EUS) is one of the most important modalities for the diagnosis of digestive tract diseases. EUS has been evolving ever since it was introduced. New techniques such as elastography and contrast enhancement have emerged, increasing the accuracy, sensitivity and specificity of EUS for the diagnosis of digestive tract diseases including pancreatic masses and lymphadenopathy. EUS-elastography evaluates tissue elasticity and therefore, can be used to differentiate various lesions. Contrast-enhanced EUS can distinguish benign from malignant pancreatic lesions and lymphadenopathy using the intravenous injection of contrast agents. This review discusses the principles and types of these new techniques, as well as their clinical applications and limitations.

Can elastography replace fine needle aspiration?

Endoscopic ultrasound (EUS) is one of the best diagnostic methods for diseases of the digestive tract and surrounding organs. Whereas EUS-guided fine needle aspiration (FNA) has been very useful for providing histological confirmation for previously hard to reach lesions, elastography is aiming to obtain a “virtual biopsy” by assessing differences in elasticity between the normal and pathological – usually malignant – tissue. A question that arises is whether EUS-elastography has reached a stage where it might successfully supplant the use of EUS-FNA in some of its clinical indications. The main indications of EUS-guided FNA are listed in this article and published data on the usage of elastography in these settings is reviewed for each one. In some of the indications, a plethora of studies have been published, notably for the evaluation of solid pancreatic masses and lymph nodes, while in others there is little relevant data (submucosal masses, left liver lesions, left adrenal masses), or elastography simply is not suitable as a diagnostic means (cystic lesions). Our conclusion is that elastography is not yet ready to replace EUS-FNA in its indications, but should complement it in various settings, especially for the assessment of lymph nodes. It can only be considered an alternative on a case-by-case basis, in situations where FNA is regarded as a contraindication. Furthermore, it could be used in conjunction with other imaging techniques, such as contrast-enhanced EUS, in order to further improve the accuracy of non-invasive EUS assessment, possibly making the case for a more limited or targeted use of EUS-FNA in selected cases.

New ultrasound techniques for lymph node evaluation

Conventional ultrasound (US) is the recommended imaging method for lymph node (LN) diseases with the advantages of high resolution, real time evaluation and relative low costs. Current indications of transcutaneous ultrasound and endoscopic ultrasound include the detection and characterization of lymph nodes and the guidance for LN biopsy. Recent advances in US technology, such as contrast enhanced ultrasound (CEUS), contrast enhanced endoscopic ultrasound (CE-EUS), and real time elastography show potential to improve the accuracy of US for the differential diagnosis of benign and malignant lymph nodes. In addition, CEUS and CE-EUS have been also used for the guidance of fine needle aspiration and assessment of treatment response. Complementary to size criteria, CEUS could also be used to evaluate response of tumor angiogenesis to anti-angiogenic therapies. In this paper we review current literature regarding evaluation of lymphadenopathy by new and innovative US techniques.

Real time elastography endoscopic ultrasound (RTE-EUS), a comprehensive review

Real-time elastography (RTE) performed during endoscopic ultrasound (EUS) is a relatively new technique which allows the evaluation of tissue stiffness, with the intent of better characterising lesions during EUS examinations. The aim of this comprehensive review was to describe the technique of RTE-EUS, as well as the clinical applications, including the study of pancreatic lesions, but also hepatobiliary, gastrointestinal (GI) tract pathology (including anal canal), lymph nodes, adrenal glands, lung and mediastinum, as well as urogenital applications. One of the advantages of the RTE-EUS technique is especially the possibility to be used in various locations accessible from the GI tract. Future developments are also briefly discussed, as elastography is a tissue characterising technique that will certainly not replace biopsy, but will rather be an adjunct during EUS examinations, due to its ease of use and low cost.