Added Value of Dynamic Contrast-Enhanced Ultrasound Analysis for Differential Diagnosis of Small (≤20 mm) Solid Pancreatic Lesions

Objective: To evaluate the added value of dynamic contrast-enhanced ultrasound (DCE-US) analysis in pre-operative differential diagnosis of small (<= 20 mm) solid pancreatic lesions (SPLs). Methods: In this retrospective study, patients with biopsy or surgerical resection and histopathologically confirmed small (<= 20 mm) SPLs were included. One wk before biopsy/surgery, pre-operative B-mode ultrasound and contrast-enhanced ultrasound were performed. An ultrasonic system (ACUSON Sequoia, Siemens Medical Solutions, PA, USA) equipped with a 5C1 MHz convex array transducer was utilized. A dose of 1.5 ml SonoVue (Bracco, Italy) was injected as the contrast agent. Time-intensity curves were generated using VueBox software (Bracco) and various DCE-US quantitative parameters were subsequently calculated after curve fitting. Univariate and multivariate logistic regression analysis were utilized. Results: From August 2020 to November 2023, a total of 76 patients (31 males and 45 females; mean age: 61.9 +/- 10.5 y) with 76 small (<= 20 mm) SPLs were included. Mean size of the lesions was 16.4 +/- 0.4 mm (range: 7-20 mm). Final diagnosis included 37 benign and 39 malignant small SPLs. On B-mode ultrasound, the majority of malignant (37/39, 94.9%) and benign SPLs (30/37, 81.1%) were hypo-echoic lesions with ill-defined borders and irregular shapes (p > 0.05). During the arterial phase of contrast-enhanced ultrasound, most SPLs (59/76, 77.6%) exhibited iso-enhancement when compared with surrounding pancreatic parenchyma. Subsequently, 82.1% (32/39) of malignant SPLs and 35.1% (13/37) of benign SPLs demonstrated wash-out in the venous phase and showed hypo-enhancement in venous and late phases (p > 0.05). Compared with benign SPLs, the time-intensity curves of small malignant SPLs revealed earlier and lower enhancement in the arterial phase, and a faster decline during the venous phase with a decreased area under the curve. Among the quantitative parameters, a lower peak enhancement ratio and higher fall time ratio were more common in small malignant SPLs (p < 0.05). For DCE-US analysis, the combined areas under the curve of significant quantitative parameters was 0.919, with 87.2% sensitivity and 86.5% specificity when differentiating between small malignant and benign SPLs. This result was better than contrast-enhanced computed tomography, which has a sensitivity of 74.4% and a specificity of 75.7%. Conclusion: DCE-US analysis provides added value for the pre-operative differential diagnosis of small malignant SPLs.