Abstract
BackgroundSecond-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.MethodsThe 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.ResultsThe 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).ConclusionsLow 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.
Highlights
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
The sensitivity and specificity of low mechanical index (MI) contrast enhanced EUS using Time intensity curve (TIC) analysis were 93.75% and 89.47%, respectively
Time needed for the contrast agent varied for both pathologies and was significantly lower in cases of pseudotumoral pancreatitis compared to pancreatic adenocarcinoma (27.87 seconds versus 56.19 seconds, p < 0.0001) (Figure 1c)
Summary
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. Contrast Enhanced Harmonic Endoscopic Ultrasound (CEH-EUS) was recently proposed as a suitable tool the differential diagnosis of pseudotumoral chronic pancreatitis and pancreatic cancer, a new generation method with high resolution [2,3]. It has the added benefit of biological material sampling without risk of tumor seeding. Second generation contrast agents and recent advances of new ultrasound systems allow better visualization of intralesional vascular signals and indicate blood flow patterns of normal and diseased tissue Because it has a better resolution than transabdominal ultrasound, CEH-EUS can represent the best way to quantify the tumor vasculature in a minimally invasive manner and with high accuracy [2]. They persist in the blood until they are eliminated by the lungs in the expired air [4]
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