Utility of virtual touch quantification in the diagnosis of pancreatic ductal adenocarcinoma

Ultrasound elastography

Physicians have used palpation as a diagnostic examination to understand the elastic properties of pathology for a long time since they realized that tissue stiffness is closely related to its biological characteristics. US elastography provided new diagnostic information about elasticity comparing with the morphological feathers of traditional US, and thus expanded the scope of the application in clinic. US elastography is now widely used in the field of diagnosis and differential diagnosis of abnormality, evaluating the degree of fibrosis and assessment of treatment response for a range of diseases. The World Federation of Ultrasound Medicine and Biology divided elastographic techniques into strain elastography (SE), transient elastography and acoustic radiation force impulse (ARFI). The ARFI techniques can be further classified into point shear wave elastography (SWE), 2D SWE, and 3D SWE techniques. The SE measures the strain, while the shear wave-based techniques (including TE and ARFI techniques) measure the speed of shear waves in tissues. In this review, we discuss the various techniques separately based on their basic principles, clinical applications in various organs, and advantages and limitations and which might be most appropriate given that the majority of doctors have access to only one kind of machine.

Recent Advances in Endosonography-Elastography: Literature Review

Ultrasonographic elastography is a modality used to visualize the elastic properties of tissues. Technological advances in ultrasound equipment have supported the evaluation of elastography (EG) in endosonography (EUS). Currently, the usefulness of not only EUS-strain elastography (EUS-SE) but also EUS-shear wave elastography (EUS-SWE) has been reported. We reviewed the literature on the usefulness of EUS-EG for various diseases such as chronic pancreatitis, pancreatic solid lesion, autoimmune pancreatitis, lymph node, and gastrointestinal and subepithelial lesions. The importance of this new diagnostic parameter, "tissue elasticity" in clinical practice might be applied not only to the diagnosis of liver fibrosis but also to the elucidation of the pathogeneses of various gastrointestinal diseases, including pancreatic diseases, and to the evaluation of therapeutic effects. The most important feature of EUS-EG is that it is a non-invasive modality. This is an advantage not found in EUS-guided fine needle aspiration (EUS-FNA), which has made remarkable progress in the field of diagnostics in recent years. Further development of artificial intelligence (AI) is expected to improve the diagnostic performance of EUS-EG. Future research on EUS-EG is anticipated.

Pancreatic Ductal Adenocarcinoma: Relating Biomechanics and Prognosis

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and carries a dismal prognosis. Resectable patients are treated predominantly with surgery while borderline resectable patients may receive neoadjuvant treatment (NAT) to downstage their disease prior to possible resection. PDAC tissue is stiffer than healthy pancreas, and tissue stiffness is associated with cancer progression. Another feature of PDAC is increased tissue heterogeneity. We postulate that tumour stiffness and heterogeneity may be used alongside currently employed diagnostics to better predict prognosis and response to treatment. In this review we summarise the biomechanical changes observed in PDAC, explore the factors behind these changes and describe the clinical consequences. We identify methods available for assessing PDAC biomechanics ex vivo and in vivo, outlining the relative merits of each. Finally, we discuss the potential use of radiological imaging for prognostic use.

Percutaneous Two-Dimensional Shear Wave Elastography for Diagnosis of Pancreatic Tumor

BACKGROUND

To investigate the efficacy of two-dimensional shear wave elastography (2D-SWE) for the diagnosis of pancreatic mass lesions.

METHODS

This ethics committee-approved cross-sectional study included 52 patients with histologically-proven pancreatic tumors (pancreatic ductal adenocarcinoma (PDAC), 36; tumor-forming pancreatitis (TFP), 15; neuroendocrine tumor, 1) and 33 control subjects. The 2D-SWE was performed for the tumor/non-tumor tissues, and SWE-mapping patterns and propagation quality were assessed.

RESULTS

Three mapping patterns were detected based on the size and distribution of the coloring areas. Pattern A (whole coloring) was detected in all non-tumor tissues and TFP, whereas pattern C (multiple small coloring spots) was detected in PDAC only. Pattern B (partial coloring with smaller spots) was detected in other lesions. The specificity and positive predictive value of pattern A for non-PDAC and those of pattern C for PDAC were 100%. The SWE value was higher in tumor lesions than in the non-tumor tissues (38.1 vs. 9.8 kPa; p < 0.001) in patients with PDAC. The SWE value in the non-tumor lesion was higher in patients with PDAC than in control (9.8 vs. 7.5 kPa; p < 0.001).

CONCLUSIONS

2D-SWE may play a role as a novel diagnostic tool for PDAC to detect a specific mapping pattern with quantitative assessment.

Modern ultrasound imaging of pancreatic tumors

In patients with solid pancreatic lesions (SPLs), the differential diagnosis must be evaluated to determine whether radical surgery, pancreatic parenchyma-saving strategies, or follow-up is indicated. Contrast-enhanced (endoscopic) ultrasonography and elastography facilitate the further characterization of SPLs. The majority of cases of pancreatic ductal adenocarcinoma exhibit hypoenhancement with contrast-enhanced ultrasonography. Elastographically soft SPLs are benign with very few exceptions, whereas stiffer SPLs can be malignant or benign. This article reviews the current use of modern ultrasound imaging techniques, including contrast-enhanced ultrasonography and elastography, for the detection and characterization of SPLs. In particular, the unexcelled diagnostic potential of multiparametric endoscopic ultrasonography to detect and characterize small SPLs is highlighted.

Elastography of the Pancreas, Current View

Ultrasound elastography (USE) of the pancreas allows pancreatic tissue stiffness assessment by virtual palpation. Two main types of USE are used. For the pancreas strain elastography applying by endoscopic ultrasound has been established for the characterisation of small solid pancreatic lesions (SPL). In larger SPL >30 mm the results are less convincing mainly due to the heterogenicity of the lesions but also by concomitant changes of the surrounding pancreatic parenchyma. The current role of shear wave elastography has to be determined. This article reviews the current use of elastography of the pancreas.

Correlation between histopathological grading and shear-wave elastography in evaluating invasive carcinoma of no special type

The present study aimed to investigate the correlation between histologic grade and shear-wave elastography in evaluating invasive breast carcinoma of no special type (NST). A total of 84 breast lesions in 80 patients (age range, 32-64 years) were retrospectively evaluated. The patients underwent B-mode ultrasound and virtual touch tissue quantification diagnosis. A semi-quantitative method was then applied in order to determine the histologic grade of the invasive carcinoma of NST according to the grading system published by the World Health Organization. Among the 84 breast lesions, 14 (16.7%) were classified as Grade I, while 29 (34.5%) and 41 (48.8%) were determined to be of Grade II and Grade III, respectively. The size of the breast lesions increased with the increase in histological grade (P<0.001). In addition, 29.3% of the Grade-III breast lesions exhibited acoustic enhancement, while the majority of the Grade-I breast lesions (78.6%) exhibited acoustic shadowing (P=0.002). Furthermore, a higher histopathological grade was closely correlated with a higher mean, minimum and maximum shear-wave velocity value (P<0.05). In conclusion, regarding the evaluation of invasive breast carcinoma of NST, the histologic grade was strongly correlated with tissue stiffness; a higher histologic grade was associated with a harder lesion. Therefore, shear-wave elastography may provide important clinical reference values.