Elastography for hepato-biliary-pancreatic surgery

Abstract

Palpation is a subjective and non-sharable diagnostic method. Recently, palpation has been supported and replaced by elastography, which provides a novel parameter of “stiffness” as a visual representation or quantified value. Today, elastography is performed using two major modalities: strain elastography and shear wave elastography. Strain elastography converts the extent of deformation during external compression into colors, displaying these colors as a strain map in a motion picture representing the relative elasticity inside the region of interest. Shear wave elastography can quantify the elasticity of a target by calculating the velocity of shear waves generated by a probe. In addition to superficial organs, elastography has also been applied to upper abdominal organs, including the liver, pancreas and spleen. The visualization of the stiffness of focal lesions in the liver or the pancreas has enabled a more sensitive and specific depiction of small, non-palpable nodules, which are difficult to depict using B-mode ultrasonography. The quantification of stiffness also enables non-invasive estimates of liver fibrosis, the risk of postoperative liver insufficiency and the risk of recurrence of viral hepatitis after transplantation. In this article, we review the major reports that have recently been published describing the effective application of elastography to solid upper abdominal organs in a clinical setting.

Self‐expandable hydrogel biliary stent design utilizing the swelling property of poly(vinyl alcohol) hydrogel

“…The results suggested both the dried hydrogels had a capacity to expand bile ducts by swelling, because the controlled force corresponds to the force, which can expand bile ducts by twice. The vertical force applied in the swelling tests under a controlled expansion force (20 kPa on the specimen) is close to the previously reported maximal value of the elastic modulus of the gastrointestinal tissue, which varies widely (range: 0.6–20 kPa) . We set the controlled vertical force for the swelling tests based on the following facts and estimations.…”

Intraoperative Characterization of Pancreatic Tumors Using Contrast‐Enhanced Ultrasound and Shear Wave Elastography for Optimization of Surgical Strategies

“…Although the sensitivity was slightly lower, our findings are concordant with results from other authors who reported sensitivity rates of 42% up to 100% for localization and characterization of FPLs using endoscopic US or transabdominal US. 6,11,[12][13][14][15][16][17]27 We found intratumoral indurations of 3 m/s or 28.7 kPa to be reasonable cutoff values during intraoperative application, with a sensitivity rate of 74.4%, though the negative predictive value was only about 41%. These cutoffs can be interpreted as initial reference values for intraoperative pancreas tumor characterization and differential diagnosis using IoSWE, but the identification or confirmation of FPL malignancy was more accurate with IoCEUS.…”

“…Thereby, reproducible and quantifiable information about the FPLs' elasticity can be gained, which correlates with the benign or malignant nature of the lesion. 3,[11][12][13][14][15][16] Studies of recent literature proved this advantage of SWE, particularly for small FPLs. 14,17,18 Another important feature that helps distinguish malignant from benign FPLs is their microvascularization.…”

“…1,6,[8][9][10] Although B-mode IoUS can identify and characterize many FPLs, small, isoechoic, or cystic lesions as well as tumorlike masses in patients with chronic pancreatitis can be hard to assess. 1,11 So far, surgeons have assessed the tumor extent by exploring the pancreas by manual palpation, trying to sense focal indurations as a malignancy criterion. With modern shear wave elastography (SWE), the palpation can be spared, as indurations can be visualized in color-coded maps.…”

“…With modern shear wave elastography (SWE), the palpation can be spared, as indurations can be visualized in color-coded maps. 11 Furthermore, SWE as a noninvasive technique enables quantification of indurations measuring the shear wave speed (SWS, in meters per second) or stiffness (kilopascals). Thereby, reproducible and quantifiable information about the FPLs' elasticity can be gained, which correlates with the benign or malignant nature of the lesion.…”