Endoscopic ultrasound elastography in diagnosing chronic pancreatitis: has the strain ratio found its region of interest?

Early detection of pancreatic tumors by advanced EUS imaging

The early detection of pancreatic ductal adenocarcinoma (PDAC) dramatically improves outcome. All available state-of-the-art imaging methods allow early detection with EUS being the best technique for exclusion of PDAC and detection of very early PDAC. Etiological differentiation of small SPL is important to guide individually tailored patients' management including radical surgery in resectable PDAC, medical (neoadjuvant or palliative intended) treatment in patients with non-resectable malignancy, pancreatic parenchyma saving strategies in some non-PDAC, and follow-up in particular in low-grade PanNEN or other small benign lesions. Multimodality EUS imaging including B-Mode assessment, elastography, contrast-enhancement and EUS-guided sampling is the most appropriate technique for diagnosis and risk assessment of small SPL. We present a review discussing modern (endoscopic) ultrasound imaging techniques including contrast enhanced ultrasound and elastography for the early detection and characterization of solid pancreatic lesions.

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.

Differentiation of Pancreatic Masses via Endoscopic Ultrasound Strain Ratio Elastography Using Adjacent Pancreatic Tissue as the Reference

OBJECTIVES

The aims of this study were to evaluate diagnostic value of endoscopic ultrasound strain ratio elastography in patients with focal pancreatic masses and to determine the cutoff value between the pancreatic malignancies and inflammatory pancreatic masses using reference areas different than those used by other investigators.

METHODS

In a prospective single-center study, strain ratio was measured in patients with pancreatic masses. After the diagnosis was established, statistical analysis was used to compare the group with pancreatic malignancies to the one with inflammatory masses.

RESULTS

Strain ratio cutoff of 7.59 provided 100% sensitivity, 95% specificity, and 97% overall accuracy for differentiation of patients with pancreatic malignancies from those with inflammatory masses.

CONCLUSIONS

Our data show high sensitivity and specificity for the calculated strain ratio. Adjacent normal pancreatic tissue is adequate as a reference area based on the inclusion criteria. Diverse cutoff values and standardization of methods in the studies published so far require further investigations, before the implementation of the method in a routine clinical practice becomes possible.

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.