Characterization of Pancreatic Lesions Using Dynamic Contrast-enhanced Ultrasound

Pancreatic cancer is currently one of the most prevalent malignant neoplasms, characterized by an increasing prevalence and a high mortality and lethality rate. It is the seventh most common malignant tumor in the general population, the fourth most deadly in both sexes, with a 5-year survival rate of approximately 9%. The lack of an early diagnostic tool and the absence of effective treatments for advanced-stage disease are the major contributors to this poor prognosis.

The diagnosis of pancreatic cancer is based on the results of multiple examinations, including various imaging modalities, until the histological diagnosis is obtained through biopsy. Transabdominal ultrasound (US) computed tomography (CT), magnetic resonance imaging (MRI), and endoscopic ultrasound (EUS) are performed to detect and stage pancreas cancer in resectable, borderline, locally advanced and metastatic. Hence, the differential diagnosis and characterization of solid pancreatic tumors represent a crucial step in identifying a suitable therapeutic strategy.

Transabdominal US is frequently used as a first-line diagnostic tool for patients with suspected pancreatic diseases. The main limitation of transabdominal US is the low accuracy in the differential diagnosis between malignant and benign solid lesions, and, considering malignant lesions, between the different pancreatic tumors (adenocarcinomas, neuroendocrine tumors, carcinosarcomas, lymphomas) since all these masses appear as hypoechoic formations.

The introduction of ultrasound contrast agent (UCA) has significantly improved the diagnostic abilities of conventional ultrasound and contrast enhanced ultrasound (CEUS) has been widely implemented in clinical practice because of the enormous quantity of information it provides, along with its low cost, reproducibility, minimal invasiveness, and safety of the UCA. In the detection of pancreatic cancer, contrast enhanced ultrasound (CEUS) achieve a sensitivity and specificity of 92% and 76%, respectively. The European Federation for Ultrasound in Medicine and Biology (EFSUMB) has recently defined the importance of contrast-enhanced ultrasonography (CEUS) in the diagnosis of pancreatic disease, supporting its use to characterize B-mode-identified pancreatic solid lesions.

Despite its numerous advantages, one of the most significant limitations of CEUS is the subjective evaluation of contrast enhancement related behavior of tissues examined. In recent years, one of the methods explored to overcome this limitation has been the Dynamic CEUS (DCEUS) which allow the quantitative analysis of UCA-kinetics in a specific region of interest (ROI). It consists of measuring the average intensity of a ROI following a bolus injection of UCA and generating a time-intensity curve (TIC). Then, multiple parameters are derived from the TIC to quantitatively characterize the different stages of the wash-in and wash-out phases. These parameters can be divided into three categories: time parameters, intensity parameters and area under the curve (AUC).