Mirjana Kalauz

Endoscopic ultrasound elastography strain histograms in the evaluation of patients with pancreatic masses

AIM To investigate the accuracy of the strain histogram endoscopic ultrasound (EUS)-based method for the diagnostic differentiation of patients with pancreatic masses. METHODS In a prospective single center study, 149 patients were analyzed, 105 with pancreatic masses and 44 controls. Elastography images were recorded using commercially available ultrasound equipment in combination with EUS linear probes. Strain histograms (SHs) were calculated by machine integrated software in regions of interest and mean values of the strain histograms were expressed as Mode 1 (over the mass) and Mode 2 (over an adjacent part of pancreatic tissue, representing the reference area). The ratio between Mode 2 and Mode 1 was calculated later, representing a new variable, the strain histogram ratio. After the final diagnosis was established, two groups of patients were formed: a pancreatic cancer group with positive cytology achieved by fine needle aspiration puncture or histology after surgery (58 patients), and a mass-forming pancreatitis group with negative cytology and follow-up after 3 and 6 mo (47 patients). All statistical analyses were conducted in SPSS 14.0 (SPSS Inc., Chicago, IL, United States). RESULTS Results were obtained with software for strain histograms with reversed hue scale (0 represents the hardest tissue structure and 255 the softest). Based on the receiver operating characteristics (ROC) curve coordinates, the cut-off point for Mode 1 was set at the value of 86. Values under the cut-off point indicated the presence of pancreatic malignancy. Mode 1 reached 100% sensitivity and 45% specificity with overall accuracy of 66% (95%CI: 61%-66%) in detection of pancreatic malignant tumors among the patients with pancreatic masses. The positive and negative predictive values were 54% and 100%, respectively. The cut-off for the new calculated variable, the SH ratio, was set at the value 1.153 based on the ROC curve coordinates. Values equal or above the cut-off value were indicative of pancreatic malignancy. The SH ratio reached 98% sensitivity, 50% specificity and an overall accuracy of 69% (95%CI: 63%-70%). The positive and negative predictive values were 92% and 100%, respectively. CONCLUSION SH showed high sensitivity in pancreatic malignant tumor detection but disappointingly low specificity. Slight improvements in specificity and accuracy were achieved using the SH ratio.

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.