Quantitative low mechanical index contrast-enhanced endoscopic ultrasound for the differential diagnosis of chronic pseudotumoral pancreatitis and pancreatic cancer

Abstract

Background: Second-generation intravenous blood-pool ultrasound contrast agents are increasingly used in endoscopic ultrasound (EUS) for characterization of microvascularization, differential diagnosis of benign and malignant focal lesions, as well as improved staging and guidance of therapeutic procedures.

Methods: The aim of our study was to prospectively compare the vascularisation patterns in chronic pseudotumoral pancreatitis and pancreatic cancer using quantitative low mechanical index (MI) contrast-enhanced EUS. We included 51 patients with chronic pseudotumoral pancreatitis (n = 19) and pancreatic cancer (n = 32). Perfusion imaging started with a bolus injection of Sonovue (2.4 ml), followed by analysis in the early arterial (wash-in) and late venous (wash-out) phase. Perfusion analysis was performed by post-processing of the raw data (time intensity curve [TIC] analysis). TIC analysis was performed inside the tumor and the pancreatic parenchyma, with depiction of the dynamic vascular pattern generated by specific software. Statistical analysis was performed on raw data extracted from the TIC analysis. Final diagnosis was based on a combination of EUS-FNA, surgery and follow-up of minimum 6 months in negative cases.

Results: The sensitivity and specificity of low MI contrast enhanced EUS using TIC were sensitivity and specificity of low MI contrast enhanced EUS using TIC analysis were 93.75% (95% CI = 77.77-98.91%) and 89.47% (95% CI = 65.46-98.15%), respectively. Pseudotumoral chronic pancreatitis showed in the majority of cases a hypervascular appearance in the early arterial phase of contrast-enhancement, with a dynamic enhancement pattern similar with the rest of the parenchyma. Statistical analysis of the resulting series of individual intensities revealed no statistically relevant differences (p = .78). Pancreatic adenocarcinoma was usually a hypovascular lesion, showing low contrast-enhancement during the early arterial and also during the late venous phase of contrast-enhancement, also lower than the normal surrounding parenchyma. We found statistically significant differences in values during TIC analysis (p < .001).

Conclusions: Low MI contrast enhanced EUS technique is expected to improve the differential diagnosis of focal pancreatic lesions. However, further multicentric randomized studies will confirm the exact role of the technique and its place in imaging assessment of focal pancreatic lesions.

Figure 1

Statistical distribution of TIC-related parameters within the two lots. (a) Distribution of median intensities between the two pathologies. (b) Distribution of the maximum intensities within the two lots. (c) Median times to peak for the two pathologies. (d) Area under the curve for the two corresponding TICs. Legend: a.u. = arbitrary units; CP = chronic pancreatitis; PA = pancreatic adenocarcinoma; Imax = maximum intensity; TTP = time to peak; AUC = area under the curve.

Figure 2

Example of CEH-EUS and TIC of pseudotumoral chronic pancreatitis. (a) Pseudotumoral chronic pancreatitis. (b) Graphical representation of the TIC trend line for the ROI corresponding to the inflammatory mass referenced to the parenchyma baseline.

Figure 3

Example of CEH-EUS and TIC of pancreatic adenocarcinoma. (a) Pancreatic adenocarcinoma. (b) Graphical representation of the TIC trend line for the ROI corresponding to the tumor referenced to the parenchyma baseline.