Identifying intact and fibrotic parenchyma in pancreatic ductal adenocarcinomas using compression optical coherence elastography

Intraoperative assessment of the condition of pancreatic tissue, including identification of “soft” pancreatic parenchyma and areas of pancreatic ductal adenocarcinoma (PDAC) are important for the prevention of postoperative pancreatic fistulas (POPFs), a predictor of the likely success of pancreatic islet isolation for transplantation, and for determining accurate resection margins in case of PDAC. The aim of this study was to analyze pancreatic stiffness using compression optical coherence elastography (C-OCE) to differentiate intact from fibrotic parenchyma and to determine the resection margins of PDAC. A total of 35 freshly excised human pancreatic specimens containing PDACs together with some of the surrounding non-tumorous pancreatic tissue derived from pancreatectomies were studied. In our investigation, calculation of the stiffness (Young’s modulus, kPa) and its color-coded 2D distribution were performed for different pancreatic tissues using C-OCE. The accuracy of the resulting data was confirmed by histological studies. The palpation stiffness of the pancreatic parenchyma was also qualitatively evaluated intraoperatively by the surgeon. Stiffness values were compared between POPF positive and negative groups. It has been shown that C-OCE can be used to differentiate various tissue types in pancreatic specimens (such as adipose tissue, acinar tissue, connective tissue, pancreatic cancer, and islets of Langerhans) and to objectively distinguish intact pancreatic parenchyma from fibrotic tissue based on quantitative stiffness assessment (p < 0.0001). A high negative correlation was observed between the percentage of acinar tissue present, determined using histological examination, and the average stiffness of the specimens, based on C-OCE data (r = -0.86; p < 0.0001). It was found that, when using a C-OCE value of < 84 kPa as the cutoff for pancreatic parenchymal stiffness to predict POPF, the sensitivity and specificity were 85% and 95%, respectively. Furthermore, our study is the first time that C-OCE technology has been demonstrated accurately to visualize the transition zone between PDAC and the surrounding non-tumorous tissues both after neoadjuvant chemotherapy and without. Therefore, the present study provides a new approach to the further rapid and objective in-traoperative assessment of the status of pancreatic parenchyma in patients, based on calculation of its stiffness using real time C-OCE data enabling improved differentiation of ‘soft’ pancreatic parenchyma from ‘hard’, as well as areas of PDAC.