Purpose: The purpose of our study was to evaluate the role of contrast-enhanced ultrasound (CEUS) with magnetic resonance imaging (MRI) and computed tomography (CT) in the pathological diagnosis of pancreatic cystic neoplasms (PCNs).
Methods: A total of 90 patients (66 women, 24 men) aged 18– 71 years were studied prospectively. CEUS was performed in all patients, whereas MRI was performed in 85 patients and CT in 69 patients. We analyzed the sensitivity and accuracy of these three imaging modalities to diagnose the PCNs. Neoplasm size, location, shape, intralesional mural nodules, septa and duct dilatation were also assessed by different radiologists.
Results: There were no significant differences in sensitivity for discriminating PCNs from pancreatic cystic lesions between CEUS and MRI (p=0.614) or between CEUS and CT (p=0.479). The diagnostic accuracy of CEUS for classifying PCNs was 64.4% (58/90), which was higher than that of CT (53.6%, 37/69, P=0.017), and lower than that of MRI (70.6%, 60/85, p=0.791). Regarding tumor size for lesions larger than 3 cm, CEUS was superior to CT in differentiating the specific type of PCN (p=0.041), and CEUS had the same value as MRI (p=0.774). Furthermore, CEUS is valuable for precisely characterizing internal structures, for instance, septa (p=0.003, compared with CT; p=0.443, compared with MRI) and nodules (p= 0.018, compared with CT; p=0.033, compared with MRI). The number of septa (p=0.033) and cyst morphology (p=0.016) were meaningful indicators in differentiating serous and mucinous adenoma. There was no significant difference in evaluating size and detecting duct dilatation among the three imaging methods.
Conclusion: CEUS compares favorably with MRI in displaying the inner structure of PCNs and offers advantages over CT. CEUS can contribute in an important way to the diagnosis of pancreatic cystic neoplasms.

Keywords: contrast-enhanced ultrasound, computed tomography, magnetic resonance imaging, pancreatic cystic neoplasms, diagnostic evaluation

INTRODUCTION

High-quality cross-sectional imaging examinations and medical checkups have significantly increased the detection of pancreatic cystic lesions (PCLs). With this imaging development, it is challenging to manage PCLs, which are mostly incidentally discovered.^1,2 The pooled rate of PCLs was higher in studies conducted in the US than in Asia (12.6% vs 3.1%).³ PCLs commonly encountered in clinical practice include pancreatic cystic neoplasms (PCNs) and nonneoplasms, which mainly refer to true cysts and pseudocysts. In the past, among all PCLs, pseudocysts were the most common; however, with imaging being more sensitive, PCNs are more frequently detected, and the prevalence of PCNs accounts for up to 60% of all PCLs.^4,5 The most common PCNs consist of serous cystadenomas (SCAs), mucinous cystadenomas (MCAs), intraductal papillary mucinous neoplasms (IPMNs), and solid pseudopapillary neoplasms (SPNs).^6,7 Neuroendocrine neoplasms (NENs) and cystadenocarcinomas are relatively less common PCNs.^8,9 The differential diagnosis of these cystic lesions ranges from benign to potentially or truly malignant lesions. Although most PCLs are considered benign, particularly those that are small in size, they have the potential to become malignant.^10,11 Thus, differentiating PCNs from nonneoplastic cysts and improving the diagnostic performance of classification the different PCNs is critical.

Currently, the imaging methods used to diagnose PCNs mainly include conventional ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI), magnetic resonance cholangiopancreatography (MRCP) and endoscopic ultrasound (EUS) with or without fine-needle aspiration (FNA).⁸ As the most convenient and inexpensive examination, US can detect cystic lesions with high sensitivity, but its diagnostic accuracy is low.^12,13 CT, due to its short scanning duration and high-quality multiplanar image display, has been regarded as a preferred imaging modality for evaluating PCLs,^14,15 but it is radioactive and has lower image resolution. MRI is deemed necessary when a pancreatic cyst is identified on cross-sectional imaging. Although MRI is considered the gold standard imaging method to evaluate these cysts in follow-up visits, it possesses some limits, which include its high costs and time-consuming process,^16–18 and the contrast agent of CT and MRI was both nephrotoxicity. Recently, contrast-enhanced sonography (CEUS), which is performed with microbubbles, a blood-pool contrast agent, is not nephrotoxic and has been increasingly used in the evaluation of pancreatic lesions.¹⁹ There are several published reports of using CEUS in PCLs, which proved that CEUS can play a vital role in improving the diagnostic rate of pancreatic cystic lesions.^12,13,20-22 However, no study has compared the diagnostic performance of CEUS with CT and MRI in pancreatic neoplasms. In this study, we prospectively compared the diagnostic capability of CT, MRI, and CEUS of 90 patients with PCNs who were finally confirmed surgicopathologically and analyzed the mainly detailed characterization of these lesions. In addition, some diagnostic indicators of serous cystadenomas and mucinous cystadenomas were analyzed.

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